Mercury Magnetics

As I mentioned earlier in the article, I had not originally intended to use a Mercury Magnetics power transformer (PT), electing instead to save a little money and use the stock DRRI PT. I’ve since changed my mind. How this came to be makes for an interesting story.

About 10 days before I was scheduled to pick up my amp at Mikey’s shop, I sent out emails to all the companies that I linked in this article. This included Mercury Magnetics since Mikey was putting their output transformer, reverb transformer and choke in my amp. Shortly after sending out an email to Mercury, I heard back from Paul Patronete who graciously gave the OK to link to their site. He also took a moment to let me know in addition to the other Mercury iron I was using, their power transformer would make an improvement in the tone of my amp. Paul invited Mikey and me to give Sergio Hamernik (an owner of Mercury Magnetics) a call to discuss the benefits of the power transformer.

I really appreciated the helpful suggestion but I hadn’t ever heard of a PT making a difference in tone, thinking the other pieces of Mercury iron would make 90% of the improvement. I did let Paul know I’d add a comment in this article saying I’d heard from Mercury and the PT would make a big improvement in the tone. He wrote me back with an interesting bit of information I had never considered. Here’s a paraphrase from the email he sent me:

The stock reissue PT does an OK job of supplying the required voltages to the circuit however the overall PT’s behavior under working conditions is not the same as the original vintage Deluxe Reverb PT. Characteristics that make the reissue PT different than the original PT involve flux density, AC regulation and primary inductance. These characteristics are a very important factor for the player that wants to nail the tonality of the vintage Blackface Deluxe Reverb amp.

Paul once again encouraged me to talk to Sergio. This certainly piqued my interest so I got in touch with Mikey and discussed Paul’s comments. We decided to get Paul on a conference call and to also see if we could speak to Sergio. We called Mercury in the late afternoon, four days before I was due to pick up my amp. Although Sergio wasn’t in, Paul spent almost 1.5 hours talking with Mikey and me about their power transformer and the rest of their iron.

Paul is a guitar player first and foremost and his enthusiasm for great tone is infectious. In addition to talking about all the good things Mercury Magnetics has brought to the industry and guitar players, he talked about what some of the cutting edge builders are doing. Mikey and Paul had very similar opinions on what makes great tone and why. It was a very informative and fun conversation. At the end of it, I certainly wanted to speak to Sergio so Paul invited Mikey and I to call again in the morning.

The next day, Mikey and I called Paul and after a brief chat, he brought Sergio to the phone. It was truly a treat to talk with Sergio and I learned a LOT about tube amps, the importance of an amp’s magnetics (the iron) and primarily, the benefits of using a Mercury Magnetics power transformer engineered for a Deluxe Reverb. As we talked, I jotted down as many notes as I could manage. I’ll share them with you now, although please keep in mind I may not have captured everything Sergio was conveying. He did a fine job though of keeping his information geared to my level of understanding.

Sergio started by asking me if I knew what modulation is. Of course I’ve heard the word but I wasn’t sure what it meant in relation to tube amps. He explained that an amplifier is a modulated power supply whereby the guitar signal is used to modulate the amp and so the quality of the power transformer affects tonality. He said the power transformer (along with the rectifier tube, a 5AR4 type) is responsible for taking the AC wall current and transforming it into the DC current used in certain parts of the amplifier. He said the power supply sets everything else up and everything depends on the character of the power supply. For example, since it helps determine the AC and DC voltages going to each section of the amp and tubes, it has a big impact on the feel of the amp.

I learned that although the stock DRRI power transformer provides the right amount of volts and amps (current) to the amplifier, the DRRI power transformer is nothing like one of the original PT’s used in Deluxe Reverbs. Sergio said among other things, the flux density and primary inductance all have to be right. As a comparison, the DRRI stock power transformer has 1/2 or less inductance on the primary than a Mercury Axiom PT. (You may recall from a previous section; inductance is the opposition to changes in current.)

He said capacitance and leakage reactance are critically important and Mercury Magnetics power transformers have lower flux density and heavier iron with better permeability. Capacitance and leakage reactance between the windings, and where the filaments are in relation to the B+ supply, really matters. Now that’s a mouthful! I think I’ll need to spend some time researching the concepts mentioned in just the last two paragraphs so I can better understand the electrical theory behind his designs. One of the best things about this project and writing this article is being exposed to new concepts. This is my idea of fun!

Sergio did break this theory down into practical examples for me. He explained the Mercury Magnetics method starts with finding the very best sounding amps and examining their iron. For example, if there is a great tone on a recording, Sergio can try to find the exact amp used on the recording and use it as the model for new iron.

Mercury Magnetics’ Axiom power transformer for a Deluxe Reverb (not for a DRRI)

The DRRI power transformer has different physical dimensions than the one in a Blackface Deluxe Reverb. Mikey has an electronic caliper that does very precise measurements so he sent these dimensions to Paul so Mercury can provide the perfect power transformer for this amp. They have the know-how to build power transformers that will sound just like one in a Blackface Deluxe Reverb. They do this by using the very best example of an original 1965 Deluxe Reverb transformer, unwinding it and laboriously documenting every nuance of how it is constructed. Then a combination of old and new technologies is used to create the very best transformer possible.

There’s a reason why guitar players seek out older amps, and this obviously is because of better tone, which I’ve come to understand is largely due to quality magnetics. I learned the magnetics available to amp builders in the 50s and 60s were made from materials optimized for the military for WWII and the Korean War. There was a tremendous overstock from the military build-up and amp builders had ready access to very high quality materials.

Modern materials are designed to be cheaper to hit price points. Sergio told us he specs custom steel to make Mercury transformers. They do enough volume of business that he can insist his steel manufacturer hand crank the steel through a gas oven, just like it was done in the 50s and 60s. Steel and copper behave differently at different milliamps so the properties of the metal must be designed and manufactured to this end. For the guitar player, this level of quality shows up in things like the ramp rate of note attack, the feel of the pick attack and better bass note response. He also used the choke as an example, where the Q-Factor (the measure of quality in a resonance system) is quite a bit different between the stock DRRI choke and the Mercury choke, so much so that it makes for an audible difference.

Sergio explained the power transformer is rated for a lot more watts than the amp produces. For example, the Mercury Magnetics Axiom power transformer for my amp will be rated at 120 watts and is capable of supporting an audio output of up to 60 watts. The general rule-of-thumb is the power transformer needs to be rated at twice as much as the maximum audio output.

Since this power transformer has specs well in excess of what the two 6V6 tubes are capable of creating, it can safely run 6L6 tubes. 6V6 tubes require only 60% of the power of 6L6 tubes. The output transformer is also capable of handling 6L6 tubes so by getting the Mercury Magnetics power transformer, I can get more power and a different tonality out of my amp than with the 6V6’s. This is a nice bonus and one I hadn’t considered when Paul first emailed me, suggesting their PT. I prefer 6V6’s in the amp but it’s nice to have another option.

Mikey asked Sergio to describe the sonic differences we might expect with the use of the Mercury Axiom reverb transformer. Sergio said the sound differences are subtle because it is such low power but if you have good ears, you’ll hear differences in “evident detail” and a “perceived wider bandwidth.”

Mikey and Sergio talked a bit about the dramatic effects of using the Mercury output transformer. Sergio likened his output transformers to a window with no glass and no screen, allowing all of the tonality of previous sections of the amp to pass through with great clarity. He explained the excellent “phase relationship tonality” (perceived as a 3 dimensional swirl) is dependent on the quality of the construction of the transformer. By comparison, the DRRI output transformer acts as dirty glass covered by a dirty screen. I couldn’t help but be reminded of the scene from the movie “My Cousin Vinny” where Vincent Gambini (Joe Pesci) disproved the testimony of a witness by pointing out with pictures how the witness was looking through dirty glass, a bug covered screen, and through trees and bushes at a fleeing car.

As a tube amp enthusiast, I’ve been reading and learning about tube amp electronics for quite some time. In this conversation with Sergio I learned a lot of things I had never considered. Of course, by now I was completely convinced their power transformer should go in my amp! You can understand why the top amp builders call upon Sergio for his expertise, designs and remarkable archive of information.

If you take a look at the Mercury Magnetics site you will find a large selection of iron to fit just about every need (www.MercuryMagnetics.com).

Sergio and Paul both told us there were very significant differences in iron on the same models of amps from the same era. Sergio spoke of a conversation he’d had with Leo Fender about amp components. Leo told him the Fender Company experienced a swelling of demand for amps when young people became enamored of guitar. Fender was just trying to meet the enormous demand so they put out specs for things like power transformers to various suppliers. The suppliers had a lot of latitude in how they meet the specs, creating a lot of variation in the parts.

Here’s another new bit of tube amp knowledge I learned from Sergio. He told me all magnetics (iron) in an amp need to be broken in over a 20 to 40 hour period of playing time. He said initially, there’s a slight harshness in the tone, which can also be characterized as a lack of sweetness. The magnetics have to be thermally and magnetically cycled. Apparently, it is similar to breaking in a speaker. Paul later told us he’s had guitar players call him up after a month to describe the new subtleties and complexities emerging from the amp: a wonderful and unexpected surprise.

After spending about 45 minutes on the phone with Mikey and me, Sergio turned us back over to Paul. I must say it was a pleasure and an honor to speak with Sergio and he couldn’t have been more gracious in taking his time to explain all of the information I’ve relayed above.

Paul and Mikey made arrangements to take the exact measurements of the bolt placement and chassis openings in the DRRI for a new power transformer. I sat back for a bit as Paul and Mikey continued where they’d left off the night before, talking about new amp ideas Mikey has been considering, which will involve creating an amp using a wide variety of power tube options. It’s too early to go into details about that though. I’ll have to save that for another article :>)

By the way, we got to know a bit more about Paul Patronete. He is a key associate of Sergio who talks with guitar players and amp builders all the time, helping people decide which Mercury Magnetics iron is right for them. You can tell he really gets off on helping players attain tonal nirvana.

Of interest, before coming to Mercury Magnetics, Paul was the General Manager for Groove Tubes for many years. I dug out my copy of Aspen Pittman’s “The Tube Amp Book – 4th Edition” and sure enough, there is a picture of Paul on the inside of the back cover. He’s also listed in the very front of the book in the “Strokes for My Folks” page and a color photograph of his Orange amps is also in the book.

Well, I’ve gone through all of my notes from my discussions with Paul, Sergio and Mikey so I guess it is time to close this chapter. I’ll be picking up my amp tomorrow although it will have the stock DRRI power transformer in it until a new one is manufactured. I sure am glad Paul took the time to talk to me, educate me, and with Sergio’s help, convince me to get a Mercury Magnetics power transformer to go along with the rest of the Mercury iron in my amp. I’ll make another trip to Mikey’s shop in Baltimore next month and I’ll be sure to let you know how it sounds, so stay tuned.

Source: https://mercurymagnetics.com/pages/news/misc/WayneReno.htm

Tim digs into a stock Orange AD200 Bass MK3. He details stripping the amp to its chassis and turning it into a point-to-point handwired amp with high-quality components.

For the past couple of months, I’ve found myself acting as bass player for a new band. It’s been a bit of a change of gears for me as I’m usually playing guitar or lap steel. In playing bass, I found myself with a need for feeding my desire for headroom — a need that can only be satiated with lots of big power tubes and stacks of speakers. I purchased an Orange AD200 bass head with their matching 4×10 and 1×15 bottoms.

In its stock configuration it’s a formidable rig to be sure. I was very impressed with the power, tone and range that it had to offer, even when trying to keep up with a very loud drummer. I played it joyfully for a few months and didn’t have a single complaint. What a happy and content fellow I was… yet… I always have this little nagging voice in the back in my head saying, “what if I changed some components? Sure I’m happy now, but couldn’t I be happier?” And so it always seems to begin with the little nagging voice that I keep listening to against my better judgment. The same voice that often leaves me sitting at my bench, head in hands thinking, why did I start this project? I was so content! WHY?

The concept of changing only a few key components was quickly forgotten once I committed to this project (and had a screwdriver in hand). I gutted the amp to the bare chassis. Out came the printed circuit board (Figure 1) with its board-mounted tube sockets, pots, transformers — everything.

Figure 1: Before gutting.

With the chassis completely stripped, it was time to lay out, measure and drill new holes for the upgraded chassis mounted tube sockets. As the new power tube sockets needed a bit more room than the PCB mounted ones, a Dremel Tool with a coarse sanding drum bit was used to enlarge the holes. Care was taken to make sure that the pin alignment made sense with the lay of the future wires before drilling the mounting holes used to bolt the sockets to the chassis. While I had the drill in hand, I also enlarged the front panel’s pot holes to accommodate the larger upgraded pots that were going to be installed. The placement for the circuit board mounting holes were also located/drilled, as was the location of the ground lugs that were going to be used in the star grounding scheme.

Figure 2: Removing the guts.

One of the most time consuming things for me when building a “one off” amp is the chassis layout. If done properly, it makes the rest of the assembly more of a connect-the-dots type of process. If done in a haphazard and incomplete way, one finds themselves drilling extra holes and routing wires in a way that may not be as professional looking or functional. In high gain designs, a poor layout can lead to excess noise and frustration.

Trying to work within a pre-existing framework is even more of a challenge. It would have been easier to start from scratch with a blank chassis, but I wanted to retain the “Orangeness” of the amp. After all, I am using the original schematic for the project, as it is a fantastic design. I just wanted to upgrade the components and make it a bit more serviceable and rugged.

After mounting the tube sockets (I prefer the Micalex sockets made by Belton) it was now time to select the components to be loaded onto the circuit boards. Unfortunately, this will have to wait for the next installment.

Selection of the parts to be used in a design with a given purpose is an important task. Almost every part in an amplifier makes a difference in the tone — starting with the quality of the AC coming out of the wall, to the power cord, all the way through to the speaker and into the room where the natural acoustics can make or break all of your hard work and tone. Some are pronounced differences, some a bit more subtle. If you add a dozen subtle nuances together, you get a pretty big nuance.

So, how does one wade through the endless amounts of caps, resistors, transformers and other “magical components” available on the market these days? Well, if you’re lucky enough to have the time and financial windfall that we all dream of having, then you can spend your life experimenting, buying and selling great gear without a care in the world. Hopefully, you’re able to develop a relationship with an artist or shop that you can trust and use them as a sounding board. Ultimately, you need to learn to trust your ears. Some of the best sounding amps that I’ve heard have been made with the cheapest, crummiest components. If it sounds right to you, than it is right!

A word of caution: Experimenting can be very fun and rewarding, but it’s easy to get too caught up in the bells and whistles. Don’t forget about the music. I found that when testing some different capacitors in one of my favorite amps that one of the caps sounded much “better” then the other. When I put the “better” sounding cap in and played, I found myself analyzing the sound in every way, from the bass response to the singing highs and, of course, how it felt. When I put the “inferior” cap in, I would start to play, get lost, look at the clock and realize that a half hour had blown by and I didn’t even listen to the cap because I was lost in the music! The “inferior” cap has lived in my amp ever since.

Figure 3: New sockets.

Figure 4: F&T electrolytics power supply caps.

My goal for this project was to “open up” the tone and feel of this already great amp. I wanted tight, slamming bass and open and airy highs with a bit more harmonic interaction. For the power supply caps, I used F&T electrolytics (Figure 4). I like them because of their reasonable size, cost, sound and feel. They are quiet and powerful enough to get good, solid bass without making the amp too fast and therefore not as musical or sweet.

For the coupling caps, I decided on Sprague Orange Drops. I use type 716 as they have a higher quality lead and are a bit more accurate they their 715 brethren. The Orange Drops, while perhaps not as sweet sounding as other choices, have a nice tight bass response with a slightly pinched top end that seems to help with harmonic content and punch. A client described their feel as “walking on packed sand instead of dry loose sand” — perfect for this bass amp.

For resistors, I use different types depending on where they are in the circuit. I don’t like to use carbon comps anywhere that the resistor may be tormented by excessive heat or where it may be prone to inject thermal noise into the signal. I will use them with regularity on the input, for example, but don’t like to use them as plate loads. Of course the brand of resistor has as large an impact as the overall construction. In places where matching and stability are important, I’ll use high-quality metal films.

The pots for this project were a mix of Clarostat Mil Spec. and CTS (CTS because I didn’t have all the values in the Clarostat). I use different types of wire throughout the amps that I build depending on the wire’s purpose. As signal wire, I use certain types of hook-up wire made for the audiophile market. For the B+ and power supply, along with the grounds on the star, I used a high-quality copper multi-strand.

Figure 5: Components installed.

Once all of the parts are selected, they’re laid out and mounted to thick glass component boards (Figure 5) with very sturdy standoffs for ease of mounting. Silicone is applied between caps to create a cushion and help to dampen any unwanted smearing of the signal or microphonics due to rogue vibrations. Paul from Mercury Magnetics sent me a set of beefy transformers that looked quite handsome dressed in their orange end bells.

With the boards made and everything in its place and wired, it was time to fire this creature up and check the voltages at key locations. Using a Variac, voltages are brought up to full power slowly. This is done for a couple of reasons. The first reason is so the electrolytic capacitors in the power supply can form their dielectrics. The second, and perhaps more important, reason is so I can keep an eye on the voltage ratios to make certain that everything is hooked correctly before I install the tubes and risk their lives (and my wallet).

One thing that I appreciate about this design is that Orange took the time (and expense) to design a power transformer and power supply that would deliver 600+ volts to the plates of the power tubes with roughly half of that on the screens. This allows you to get the benefits of high plate voltage (headroom and power) while maintaining a safe operating environment for the power tubes. Now that we’re certain everything is safe and sound, the power tubes (Svetlana “winged c” KT88s) and preamp tubes (mix of NOS RCA and Sylvania) are installed and biased.

Though I’ve been building and modding amps daily for a few decades now, every so often I’m surprised by an end result. With the first strum of the strings, I was floored by the increased headroom, clarity and bell like tones coming out of this powerful amplifier. The change and added versatility in preamp/overdrive section was a pleasant surprise as well. While originally designed as a bass amp, it is fantastic for guitar and pedal steel as well. In retrospect, I’m very glad that I went through the trouble and expense to rebuild this amplifier. It has become my “go to” for almost every application. Long live headroom and power!

Source: https://mercurymagnetics.com/pages/news/PremierGuitar/PremierG-22.htm

Many people, including more than a few amp techs, have the mistaken belief that when it comes to a power transformer, “volts-is-volts,” and upgrading a PT won’t have much of an effect on a guitar amplifier’s overall tone. Not so! My tone transmogrifying tweakers!

The audio circuitry of your amp is completely dependent on the quality of its power supply. The very first component in this food-chain-of-tone is the power transformer. It makes the necessary connection between your amp and the power company. How it behaves sets the standard for your amp’s performance. The PT has a profound affect on your amp’s sonic characteristics especially its ability to handle musical dynamics. What this means to you is crisper note attack, better note separation, and added sparkle in the upper mids and treble frequencies. And keep in mind that with a properly-designed power transformer you’ll hear all-around higher definition with the amp’s clean and dirty tones.

Do not assume that all amp manufacturers know this, or that they have provided your amp with the best possible transformers (unless they are already equipped with Mercurys!). Instead you might just be stuck with low-cost, short-cut transformers. Remember, there are dozens of ways of building cheap transformers to meet certain voltage values but they all fall short of giving your amp the best musical qualities—that’s the magic of Mercury Magnetics!

Which turns you on more? A tranny built only to please a volt meter — or one that maximizes the sonic potential of your amp? You no longer need to be a victim of the sonically-challenged. It’s time to liberate your amp with the only guitar amp transformers actually designed for better sound—Mercury Magnetics.

Source: https://mercurymagnetics.com/pages/_misc/FAQ.htm#The_Power_Transformer

While Michael Bloomfield was playing cranked up blonde Fender Bassman and blackface Twin Reverb amplifiers, Marshall 100 watt stacks suddently appeared thanks to The Who, Jimi Hendrix, Cream and Led Zepplin. Throughout the ’70s, rock was dominated by the sound of a Les Paul and Marshall amps, but despite its reputation as the ultimate rock machine, all four-input, 100 watt Marshall model “1959” heads are not the same….

The first 100 watt Marshall amps appeared in late 1965,and despite Marshall’s decision to drop tube rectifiers for the less forgiving, harder sound of solid state diode rectification, the “Plexi” 100 watt heads remained more closely related to earlier Marshall amps inspired by the tweed Bassman than the Super Leads that would follow. In the early ’70s, the 50 watt model “1987” head and 100 watt Super Lead were gradually modified to produce more gain faster, and the bright channel was pushed to a punishing level of thin, ear-shattering brightness, while Channel II remained too dull and bassy to be used alone.

We acquired a 1973 Super lead—the last year before Marshall switched to printed circuit boards—for the modest sum of $1,000, made possible by a recent Dagnall replacement output transformer. Two .022 mf caps had been replaced with Orange Drops and another removed altogether in a futile effort to reduce brightness and gain—other-wise, the original Super Lead circuit remained intact and unmolested. Our plan was to run the amp at approximately 60 watts with just two EL34s, requiring the amp to be set at half the rated speaker impedance of our 8 ohm 4×12 Avatar cabinet, loaded with two Celestion Gold Alnico 12s and two “Hellatone” 70th Anniversary G12H 30s.

As we discussed this project with Jeff Bakos, he mentioned that the 100 watt Super Leads not only sound very different from the 50 watt heads in ways that transcend a mere increase in power, but he also felt that the 100 watt Super Lead amps sound better with just two powertubes instead of the full compliment of four…“That’s very common down here—I know a lot of layers who prefer that sound.” We also consulted with Sergio Hamernik of Mercury Magnetics on a suitable replacement for the modern Dagnall OT, and he suggested the ToneClone’69 Marshall self-leaded version. “Self-leaded” means that the actual wires wound within the transformer are extended to connect directly to the amp, rather than smaller diameter lead wires being attached to the transformer internally. Installing a self-leaded version is a bit of a bitch, since you are cutting and bending much heavier gauge wire to fit in tight spaces, and the insulation must be scraped off the wires before soldering. But Jeff had been here before,and all was taken in stride.

We also noted that the original power transformer in our ’73 Super Lead was similar to those found in the early Plexi100 watt amps with plate voltages well above 500 volts.

Our amp measured 522 volts, while the plate voltage on most post-plexi 100 watt “1959” amps are usually lower—around 460 volts. The “hotter” transformer in our Super Lead produces a comparatively higher and less compressed distortion threshold, and if not for our pair of NOS MullardEL34s, we might need to be more selective about choosing current production tubes that can withstand +500 volts on the plates. Jeff was confident that JJs would hold up, less confident of Svetlanas.

We took the Marshall home and initially ran it with three spare Telefunken 12AX7s just to see if they sounded as sterile in a guitar as we had recalled in the past. They do. We could hear a distinct improvement in the mid and bass tones with the new transformer, but the bright channel remained far too bright to be used alone, even with a Les Paul. While we could manage to knock down some of the treble and acquire a decent tone with the bright channel set on “3” and the bass channel patch with the volume on “6,”pushing Channel II so far above the level of bright channel introduced an indistinct woofiness we didn’t care for. The next day we returned to Jeff’s shop for his standard Marshall 4-banger input channel mod, which simply involves moving the original .005 mf bright cap on the bright channel to the basier Channel II. We had done this before with our ’69 50 watt and a vintage PA20, and it unerringly transformers the sound of the notoriously dull Channel II to a fat, warm, musically rich and bright sound that works perfectly every time. We also replaced the two Orange Drop caps with Mallory 150s and pulled the super hi-fi Telefunkens, replacing them with NOS RCA 12AX7s—the warmest, creamiest pre-amp tube ever made.

With the Super Lead thus optimized and tweaked, its voice was transformed from an angry soprano chain saw to a classic Marshall with all of the requiste thick,rich, historic hall of fame tones at our fingertips. We could mine brilliant clean tones on “3” at a usable volume level that revealed all the gorgeous detail of the vintage patent number pickups in our Historic Les Pauls, and our Stratocaster, Nocaster and Les Paul Junior all sounded equally good. Add Fender outboard reverb and you do indeed have the Twin from Bloody Hell.As Jeff predicted, the big power supply in the Super Lead also produced a much more formidable and impressive presence than a typical 50W. Yes, the Super Lead is still a beast, tamed for your consideration and our enjoyment. But if classic Marshall tone is the sound you crave, a properly groomed Super Lead is hard to beat, and given today’s boteek and vintage amp prices, it’s a solid steal.

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Boy have I got a treat for you guys!!! As you know I am a big fan of Mercury Magnetics transformers and have been a dealer for many years now. Their products are excellent as well as their customer service. The Mercury Magnetics line is quite extensive and they will do custom pieces as well.
I have been working with Sergio Hamernik for almost a year now on an exclusive interview all about guitar amp transformers. In this interview Sergio talks about how transformers affect your amp’s sound and feel, if transformer size matters and how it affects tone, what a choke is and much more information.

Mercury Magnetics is the leader in guitar amplifier transformer manufacturing. I have personally used their iron in many repairs, restorations and custom builds over the years. It never ceases to amaze me when I use a set and listen to the amp after the project is complete. It’s almost like a blanket was taken off of the sound and you are listening with “3D glasses.” The feel of the amplifier becomes much more dynamic as well. In my opinion “your amp’s transformers truly are the heart and soul of your amp.”
In this exclusive interview with Sergio Hamernik (the man behind the scenes at Mercury) some basic questions that all relate to the tone and feel of a guitar amplifier. His answers are forward, straight to the point and insightful.

300guitars: Why should guitar players care so much about the transformers in their amps?

Sergio Hamernik: When a player has to struggle with his amp then there’s really not much of a reason to play it. The tonal quality and performance of a tube-type guitar amp is largely determined by its transformers. Where there is great “tube tone,” you’ll always find “great sounding transformers” making it all happen!

Once you get past the player’s talent/ability, it’s all about the tone. If an amp doesn’t produce desirable tone, the window of inspiration closes and gets replaced with fatigue for both the player and the listener.

These days musicians who choose to play an electric guitar are only as good as their technical awareness and development allows them to be.

Transformers are the most important and most expensive components of guitar amp’s parts list. Also, they are the only components designed and built specifically for that amp, unlike the rest of the components — the resistors, capacitors and even vacuum tubes. These other components are considered to be “universal application” parts — meaning not just for making guitar amp tone. The electronics industry commonly uses these same components for medical, industrial, radio and many other applications. You certainly couldn’t fit or use guitar amp transformers for any of these other applications without offending someone.

Transformers are the key to providing that unique signature tone. It’s the transformers that differentiate one amp brand or sound from another. Here’s another way to look at it — all amp builders have to deal with the same limited choices from a small pool of vacuum tube manufacturers and other off-the-shelf component requirements (resistors, capacitors, etc.). This is NOT so with the transformers. Although there are plenty of generic transformer designs available that service the “power requirements” of an amp, you wouldn’t want to use these awful-sounding devices in your guitar amps. Likewise it’s not a coincidence that most of the best-sounding amp builders, modifiers, and repair techs begin their craft and finish it with enviable distinction, relying on their choice of transformers.

300guitars: Would you explain, in guitar player terms, what power and output transformers are?

Sergio Hamernik: Well, I really don’t like to lump all guitar players into one category. Making assumptions here (be it charitable or not) just doesn’t seem fair to me. Each player has their own level of interest and technical understanding on this subject. So I’ll split my answer into three different groups of definitions and let the player choose the one that suits them best.

In basic guitar player terms: It’s magic!!

In technician terms: A device applying mutual inductance in an efficient manner, so that circuits with different voltage/current requirements can correspond to each other.

In engineering terms: Transformers are electrical devices consisting of a magnetic-core and two or more coils (commonly referred to as windings) inductively coupled as circuits for the transmission of alternating-current energy from one closely coupled coil to another usually at a different voltage and current value. Transformers are also used for matching impedances between the signal generating source and the load.

300guitars: How does the power transformer affect the sound of your guitar? The sound comes from the output transformer right?

Sergio Hamernik: Yes the amplifier’s sound does come out of the output transformer, but where does it all begin? While an output transformer is vital to an amp’s ultimate tone, it simply can’t do it alone. The power transformer is the first step in building tone and in setting the standard of performance that the tubes and output transformer utilizes.

The output transformer depends on the power transformer for determining the maximum amount of power the amp can put out. The power transformer is also a major contributor for the overall feel of the amp. Such as punch through (the oomph factor), note attack, a perceived larger/wider soundstage presence and most importantly, the speed or reaction time of the amp’s audible response to the player’s sense of touch and playing technique. Tamper with that in any way by using cheap “dumbed down” power transformers and your audience may confuse your amp’s tone with the sound that is made by farting into a pillow!

A puny power transformer will deliver puny tone no matter how good the output transformer is. A good output transformer is also not intended to be a problem fixer or a turd-polisher. Garbage in is always garbage out. So please don’t shoot the messenger because the power tranny just ain’t cutting it.

Output and power transformers are actually close cousins. Doing similar tasks, one matches and isolates the speaker from the amp and the other one matches and isolates the amp from the power company. Peace keepers of a sort, preventing tubes from frying the speakers and preventing the power company’s energy from frying the amp and people connected to it.

300guitars: How does the output transformer affect the amps sound and feel?

Sergio Hamernik: An output transformer is the last component of the audio chain. The amplifier’s voice. The final word that reaches the speaker. Because all vacuum tubes were never really designed to distort intentionally, the weight of producing desirable amplified guitar tone falls heavily on the transformers. The output transformer’s job is to coax, extract and even irritate the power tubes into tone-friendly distortion. Ever wonder why solid-state amps have always played second fiddle to tube amp tone? Is that simply because of not employing tubes or of not having an output transformer? At the very least, it’s something to think about.

The output transformer determines how the amp sounds like from fully clean (sweet with a touch of sparkle) to fully over-driven (chainsaw) distortion, and everything in-between.

By the way, the term “clean” as used in guitar amp speak is a bit of a misnomer. There is no such thing as a distortion-free guitar amp. “Clean” simply refers to less distortion. There is an intimate inductive/reactive relationship between the output transformer (coils) and the speaker voice (coils) that also back-washes into the power tubes and influences that “clean to dirty” range of distortion. The quality of the output transformer determines how well the production of tone is executed by the amp — those notes that float between the strings which are created by overtones, chimes, bell tones, sustain, etc. Poorly made output transformers tend to gargle out, squash and mask those overtones.

The output transformer is also responsible for how efficiently the audio power of the amp transfers to the speaker (load). Ultimately, the player issues the final report card for the performance of the amp and the output transformer with comments like “clarity,” “articulation,” “loudness,” “break-up,” “grit,” “glassy,” “grind,” “dirty,” “woody,” “mushy,” “mashed,” “fuzzy,” “dark,” “cloudy,” and so on. There are hundreds of guitar amp speak descriptions and euphemisms out there which capture their emotional response (players and listeners alike) to what is coming out the amplifier’s window.

The mighty output transformer. Loved and hated by so many. Still one of the most misunderstood components of a guitar amp. 80 years and going strong. Go figure….

300guitars: When it comes to transformers does size matter? How?

Sergio Hamernik: I can almost hear my wife saying “now that sounds like a guy question.” Actually, in most situations, transformers and chokes make a good case for “bigger is better.”

A power transformer that is undersized for the job will run hotter than a bitch kitty. The amp is unable to be pushed — collapsing under weak, sagging voltages. It’s unable to keep up with the demands a player puts to an amp. The amp slows and has a tendency to cough out notes when played clean, and honk or bark out the notes when overdriven.

Another symptom of undersized and/or poorly designed power transformers is the phenomenon of “tone drift.” You know this is happening when the amp (common with some early Fenders and half of today’s 100 watt amps) starts off with decent tone for the first hour or so, then somewhere around two hours later the tone begins to change and not for the better. The internal temperatures of the transformer reach their peak and begin detuning the voltages and power the amp sees. This is caused by the changes to the resistance of copper. As the temperatures become excessive, the amp’s tone drifts. Remember rich amplifier tone needs to be well fed.

An undersized output transformer will act more like a suppository to amplified guitar tone than a big open window, which is its main purpose. Contrary to popular myth, there is no tone magic that occurs when you force feed an output transformer into alleged saturation or intentionally under power it with a dinky power transformer.

The term “output transformer saturation distortion” comes out of poor guessing by people who really don’t understand how tubes and transformers work together to produce music friendly harmonic distortion. If an output transformer reaches true saturation, all bass frequencies will disappear, the mid-range will sound dark and fuzzy with lower volume — leaving the treble frequencies tinny and brittle sounding. Does that sound desirable to you?

So it’s not the transformer itself generating that saturation effect on overdriven guitar tone. Good output transformers are designed to operate at low flux densities (loads of inductance). That low flux makes it difficult to saturate an output transformer. So the output transformer doesn’t get the credit or blame for that “saturated” sound. The actual source is in the push-pull power tube plate circuit reacting/saturating to the changing impedance it sees in the primary coil of the output transformer as its flux density changes with the changing frequencies and fluctuating power coming into it. The saturation phenomena (when it appears) is mostly happening in the tube.

If one wants to intentionally use a dinky power transformer to achieve tone magic (yes some have tried it, believe it or not). They could save themselves a bunch of money and buy that pillow I mentioned earlier for similar results.

Bigger is better for chokes if you have the room for it on the chassis. Assuming the same value of inductance, more iron and copper will let more power through and it will run cooler as well. This is because of lower DC voltage resistance with the extra copper involved. More voltage being available to the tubes means more power out of the amp.

300guitars: What is the choke for and why do you offer so many models?

Sergio Hamernik: Originally chokes were used in guitar amps to extend the life of vacuum tube rectifiers nearly tripling their life expectancy. They behave as a quasi current spike shock absorber. Chokes help capacitors smooth out any ripple that may be present on the DC voltage. The goal here is to always try to get the cleanest voltage to the tube circuits. Caps by themselves do a pretty job of it. But the choke is a multi-tasker. Along with doing a nifty job of smoothing out ripple, the choke does something else that makes it a significant contributor to the amp’s final tonal character. Because its connected in series with the rectifier and not tethered to ground like a cap, the choke (being an inductor) works nicely as a current regulator. And it keeps the current from decreasing as much as it would if there were only caps involved.

This nearly constant current available from the power supply, courtesy of the choke, makes for an ideal platform to make the best possible tone. Simply put, changing the value of the choke changes the tone and behavior of your amp.

Why so many varieties of chokes? Since chokes are a significant link in the audio chain, a one size fits all approach would be a great injustice to all guitar amp owners. Choke values are a finesse point, a fine tuning that helps to extract the most favorable tonal characteristics from an amp. We even offer a “shift on the fly” option with our multiple-value Multi-Chokes. One choke with several choices of inductance to help the amp builder find that sweet spot.

There is one last benefit to using chokes and it’s the most overlooked attribute. When a choke is connected between a couple of caps, a form of a low pass filter is created. What this means is the choke blocks high frequency garbage on the AC line from mixing with the guitar signal and causing all sorts of sonic collisions during the process of amplification. Let us not forget that we live in an electronic age far more complicated than the 1950s or 1960s. There are all sorts of things contaminating our power before it hits our amps. Computers, TVs, BTL cable services superimposed on our power lines, you name it, are all sources of noise we don’t want in our amps.

You’d be surprised to find out how many amp builders substitute a resistor for a choke just to save a few bucks and lose out on the choke’s very cool advantages. Almost all of the great vintage amps had chokes (Marshall 50 & 100 watt, Vox AC30, Fender Twin, Showman, Super Reverb, Vibroverb, Pro Reverb, Deluxe Reverb, etc.). The builders back then were taught tube theory and understood the relevance of the choke in their designs.

300guitars: Would a Mercury replacement reverb transformer make the reverb in an amp sound better?

Sergio Hamernik: That depends on how lousy the original one was. Reverb transformers are wound similar to guitar pickups. Lots of turns with very thin wire. Which adds to the expense of building them. Many companies skimp on materials to keep their costs down as a result.

We believe that the low level signal (barely a whisper) going into the reverb transformer is quite fragile in nature and anything less than using the best materials and winding techniques would cause it and its tone harm. According to our customers that have upgraded their reverb transformers with ours, they report better performance, higher def, a more lush-sounding reverb, etc. Based on that, my answer is yes — or your money back.

300guitars: Is it easy to upgrade an amplifier to a set of Mercury transformers?

Sergio Hamernik: Heck no! It’s not at all easy. Therein lies the rub. This is why we have the great divide between disappointing “corporate” tone and a thriving (yet inconsistent) boutique amp market.

How much hassle and expense are you willing to put up with to get your ideal tone? If merely swapping out tubes will improve tone, then why are we still missing so much of it today? If simply plugging things in or out made for better tone, then all the big amp companies would have nailed it decades ago and we wouldn’t have the need for this interview. But no, it’s not that easy. Quick, cheap and dirty (non-transformer) amp fixes are not worthwhile timesavers. They tend to act more like tinsel and don’t do much for real tone problems. My wise old grand dad once said, “Putting powdered sugar on a turd, doesn’t make it a doughnut.”

Upgrading to Mercury transformers requires technical expertise and a morbid fear of being electrocuted. There are potentially lethal voltages present, a ship load of wires coming out of these things to further complicate matters and requiring a good share of installation elbow grease to boot. A person should be schooled in electronics and not sexually frustrated. A steady hand goes a long way in doing a good install. It shouldn’t be a D.I.Y. project no matter how simple it may look to the casual observer. We have techs all over the planet that are willing to help and do a good job with safety first. Transformers are expensive and labor intensive to install.

Those who are ready to make such a commitment/sacrifice (who needs kids anyhow?) will be rewarded for their efforts. Don’t take my word for it, just read our testimonials. We have a bunch of them all unsolicited from players, amp builders and amp techs, who were impressed enough to write to us telling everyone that it was well worth it.

300guitars: It seems that tubes and big hunks of iron (transformers) are very old school technology. Is there anything new on the horizon at Mercury?

Sergio Hamernik: Playing a guitar is even older school. There isn’t anything modern about an electric guitar. But, what makes an electric guitar “electric” is the fact that it depends on the rules of magnetism. The pickups on an electric guitar are made of coils of wire responding/reacting to a changing magnetic field, so are the voice coils in speakers. And let us not forget the power transformer, choke and output transformer in an amplifier are doing their jobs through magnetic fields — literally completing the link between a player’s finger tips to the player’s and listener’s ears.

My point being that if you replace your amp’s transformers for something else, you might as well replace the electric guitar with something else. So happily, we’ll stay stuck with big hunks of iron and hang on to our electromagnetic guitars! This means that tubes, which are not magnetic devices, could eventually be replaced by other devices such as high-voltage Field Effect Transistors as long as they’re mated to right kind of transformers. This is stuff that you don’t really need to know, but it’s a point of interest. There are a lot of motivated people out there that are fed up with the poor quality of tubes today and might be able to make tube substitution a reality someday soon I hope.

What’s new on the horizon at Mercury? A bunch of stuff. A cool new line of transformers that will give the next generation of players a unique voice of their own. Vintage is great, but we also want to encourage a new generation of inspired song writers and players to continue guitar based music. It’s all about the tone that will help seed this.

We are in the process of designing, developing new Upgrade Kits, pre-packaged transformer sets for those who are not satisfied with the tone of their present day amps. It’s our passion.

And, possible amp tone clinics. If that is what players want. We are also working on things that are a bit beyond the horizon which I’ll talk about sometime later.

300guitars: Thanks Sergio for taking the time for this most informative interview!!!

Sergio Hamernik: Thanks Billy for this interview and for giving a damn about all this stuff we call tone. Your passion clearly shines through on your website. It’s people like you that keep it all going and compel us to continually raise the bar for the guitar playing community.

I also want to apologize in advance if I offended anyone’s sensibilities with any comments I may have made. I will learn to live with the guilt….

Source:  https://mercurymagnetics.com/pages/news/300guitars/300g-02.htm

Shop for Amp Transformers

By Billy Penn

Did you know that tube-based guitar amplifier transformers are unusual and very different from industrial as well as audio transformers? And did you also know that it is impossible to engineer the “perfect” guitar amplifier power transformer from strictly “by the book” specifications? Interestingly, almost all of the great-sounding amp transformers contain either flaws, “happy accidents,” or have other issues in their construction that were not part of their original specifications.

Your quest for truly inspirational and superior tone has led you to the final link in the chain – Mercury Magnetics. Premium guitar amplifier power transformers, output transformers and chokes.

Transformer sets are often misunderstood, yet vital musical components. They’re integral to the nuances of your guitar amp’s sound. Far more than tubes, speakers or other amp components, the transformers establish the platform for shaping your amp’s unique sound.

Today’s players are more informed and demanding than ever. They hear the differences and know that both transformer design and build-quality have a dramatic effect on their tone. Indeed, if your tube-based amp is suffering from bland and unexciting tone then it’s probably related to low-end or poorly designed transformers. As amp designers, techs and manufacturers have discovered, the practice of dumping generic, low-bidder transformers into their amps doesn’t cut it any more. And now you know why.

Within the player community no other company commands as much respect as Mercury Magnetics. You can depend on our uncompromising, fanatical build quality, consistency and reliability.

We always maintain a steady flow of gear arriving for review, but sometimes we also employ a fascinating if time-consuming research strategy that involves logging onto eBay, picking a broad category such as “guitar amplifiers,” and settling in for as long as it takes to patiently scroll through every page of listings. Yeah, that’s often 50 pages or more, but since we can’t possibly think of all the items that might interest us and search for them by name, it’s far more revealing and productive to just hunker down and scroll. Rarely do we fail to find something intriguing that would have otherwise been missed, and such was the case on a morning in August when we stumbled on a listing for a 1959 tweed Deluxe. Were we looking for a tweed Deluxe? Nope. Wouldn’t have crossed our mind at the time…. We had already reviewed 5E3 reproductions from Fender, Clark and Louis Electric within the past 3 years, and we have frequently referenced our 1958 Tremolux as being our desert island #1. Isn’t a Tremolux just a tweed Deluxe with tremolo in a bigger box? No… not even close. That would be like saying you wanted to date a blonde – any blonde. For the record, our fixed bias Tremolux possesses a cleaner tone with a bigger, booming voice created by the taller Pro cabinet. The Two Fifty Nine is a completely different animal….

Sporting a February 1959 date code on the tube chart, the ’59 had been listed by a seller in Arkansas who turned out to be Tut Campbell, formerly a well-known guitar dealer in Atlanta. Still buying and selling gear, Campbell had described the Deluxe as being in original condition with the exception of a replace output transformer – a big old mono block Stancor dating to 1957. Given the otherwise original condition of the Deluxe, which included the Jensen P12R, we made Campbell a “best off” below his asking price and scored the amp for $1,850 shipped. We wouldn’t say we stole the Deluxe, but it seemed a fair price of admission for the opportunity to experience and explore still another rare classic and supremely worthy piece of Fender history on your behalf.

The Deluxe arrived with the big Stancor dangling from the chassis despite Campbell’s careful packaging. Wasn’t his fault, really – in a feeble effort to avoid any additional holes being drilled in the chassis, the fellow who installed the Stancor in the ’60s had merely tightened set screws over the small tabs at the base of the heavy tranny, which was designed to be mounted upright – not hanging upside down in a guitar amplifier. Of more concern was the fact that while the amp was lighting up, there was no sound…. Well, we’ve been here before, so we made a call to God’s Country and the Columbus, Indiana domicile of Terry Dobbs – Mr. Valco to you. We had already set aside a spare output transformer (Lenco, McHenry, IL) that had been the original replacement installed in our ’58 Tremolux when we first received it, replaced with a Mercury Magneticsfor our June ’07 review article. Mr. Valco cheerfully answered his phone and as we explained the situation with the Deluxe he agreed to walk us through the installation of the new replacement – a simple process involving four lead wires being connected to the rectifier and output tube sockets, and the speaker jack. As long as you put the correct wires in the right place, a piece of cake, and we had the new tranny in within 10 minutes. Pilot lamp and all tubes glowing, still no sound…. Valco patiently guided us through a series of diagnostics with the multi-meter and the Deluxe was running on all cylinders, pumping 380 volts. Stumped, and with the hour growing late, we called it a day. Leaving the mysteriously neutered Deluxe chassis on the bench until tomorrow.

Morning came with a whining voice delivering a plaintive wake up call – “It’s got to be something stupid and simple….” Inspired by a huge steaming mug of Jamaican High Mountain meth, we sat back down at the bench, tilted the innards of the Deluxe chassis forward beneath a bright halogen desk lamp and peered in for answers. We began slowly examining the chassis in sections, looking for broken or dull solder joints, loose or broken wires, while gently pushing and prodding wires and connections with the eraser tip of a #2 pencil as we had seen Jeff Bakos do so often at his bench. After ten minutes or so we were about to give up, when we turned our attention to several places where the circuit was grounded to the chassis adjacent to the volume and tone pots, and damned if a solder joint for one of the uninsulated ground wires hadn’t separated from the chassis. No ground, no sound, and as soon as we had restored the solder joint the Two Fifty Nine arose from the dead with a mighty A major roar.

The amp was indeed remarkably well-preserved in all respects, with the typical amber patina of old tweed. The burnished chrome control panel remained bright and clean with no corrosion, the original handle remained intact, and a couple of small ciggie burns on the edge of the cabinet added a stamp of historic legitimacy to the Deluxe’s pedigree. The top half of the Jensen’s frame was coated in a fine film of red clay dust from the Delta, and while the cone was in remarkably good shape with no tears, an audible voice coil rub called for a recone. We would send the speaker to Tom Colvin’s Speaker Workshop in Ft. Wayne, Indiana, requesting that he leave the original unbroken solder joints for the speaker wires intact if possible.

Meanwhile the first order of business was to listen to an assortment of NOS tubes from our stash, and audition no less than a half dozen speakers. Different sets of power tubes and individual preamp tubes will sound surprisingly different, so we started out with a matched pair of NOS RCA 6V6s, a GE 5Y3 rectifier, and an RCA 12AX7 and 12AY7. From there we subbed in a dozen different RCA, Amperex, Tesla and GE 12AX7s, noting varying levels of brightness, warmth and intensity among them all. For an edgier, more aggressive voice, the GEs and Amperex typically deliver the goods, while RCAs produce a slightly warmer, richer, fuller tone. We also experimented with a 12AT7 and 12AX7 in place of the lower gain 12AY7, and while those tubes ramp up gain and distortion faster and with more intensity than the 12AY7, they seemed like overkill for us. Our Deluxe possesses a tone of gain using the stock 12AY7.

Rather than repeatedly reloading the Deluxe with different speakers, we used a Bob Burt 1×12 cabinet built from 100-year-old pine for our speaker tests. The original Jensen had never been pulled from our amp, but multiple speaker replacements in an old Fender inevitably cause the speaker mounting screws to loosen in the baffleboard, making speaker swaps unnecessarily clumsy and complicated. When we do run into loose mounting screws, we simply run a few small drops of Super Glue around the base of the screw and surrounding wood. Allow to dry and your screws will stay put provided that you don’t torque the nuts on the mounting screws like an idiot with a socket wrench. Don’t be that guy,

We tested a range of speakers that included a Celestion G12H 70thAnniversary, Colvin-reconed ’64 Jensen C12N, Eminence Wizard, Private Jack, Alnico Red Fang, Teas Heat, Screaming Eagle, Red, White & Blues, and Warehouse Green Beret, Veteran 30, Alnico Blackhawk and Alnico Black & Blue. The Alnico speakers generally produce a tighter, smoother, slightly more compressed tone, with a variable emphasis on upper mid-range and treble frequencies, while the speakers with ceramic magnets possess a wider, more open sound. Higher power ratings of 75W-100W offered by the Red, White & Blues, Screaming Eagle and Warehouse Blackhawk typically translate into more graceful handling of bass frequencies, and in a 20 watt Deluxe, zero speaker distortion, for a clean, powerful voice.

Let’s cut to the chase with speaker evaluations, shall we? It has become clear to us that even after reviewing a dozen speakers in as much detail as mere words allow in a single article, many of you remain uncertain about which speaker to choose. No kidding. We would absolutely love to hand you a single magic bullet when it comes to speaker swaps, but here’s the dirty little secret about choosing speakers…. The overall character of the amp you will be installing your new speaker in is critical, and to some extent, the type of guitars and pickups you play most often are important, too. Tailoring your sound with the unique gear you play is not a one-size fits-all proposition – you have to invest some thought into the process. Are you going for a classic “scooped” American Fendery tone, or something more British, with a bit of an aggressive edge and upper midrange voice? Are you playing guitars with single coil pickups or humbuckers? Is there a specific, signature tone you are searching for, or are you playing a wide variety of musical styles that requires a broader range of tones? Do you like the more open sound of speakers with ceramic magnets, or the smoother compression of Alnico? What are you not hearing from your amp and the speaker that’s in it now? Do you want a brighter tone, darker, better bass response, or fuller, more prominent mids? Do you want to really drive the speaker and hear it contributing to the overdriven sound of your amp, or do you want a big, clean tone with no speaker distortion in the mix? The truth is, if you don’t know what you want, you are far less likely to get it. On the other hand, nothing is accomplished with paralysis by analysis. To be perfectly honest, there are lots of speakers made by Celestion, Eminence, Warehouse and, if you can wait long enough for them to break in, Jensen, that we could and would be perfectly happy with, but we would also choose them carefully, taking into account all the factors mentioned above. After a couple of days spent swapping speakers, we ultimately concluded that we preferred the ’64 C12N for a classic tweed Deluxe tone, and a broken-in Celestion G12H 70th Anniversary for the most mind-altering 18 watt Marshall tone we have ever heard. Seriously. More on that in a minute….

Having split more than a few hairs with our speaker swaps, it was time to start picking nits off of gnats with some output transformer evaluations. We first contacted Dave Allen of Allen Amplification, who also stocks Heyboer transformers built to his specs. We found a variety of appropriate output transformers on Allen’s site that offered subtle variations on a stock original Deluxe OT, and we asked Dave to describe the TO26 model we wished to try in the Deluxe:

“The TO26 was intended as a hot rodding upgrade to a stock Deluxe Reverb OT. While maintaining the stock 3-1/8” mounting centers, its fat stack of hotter core steel and multi-tap secondary make it a good choice for builders wanting to maximize the performance of a pair of 6V6s and who may also want to push the envelope with 6L6/5881s while still being able to clear the speaker in a stock cabinet. There are physical limitations in small amps, so its short low profile is welcome. The orientation of the laminations is also good for low hum pick up from the power transformer. I found that an OT mounted the tall way (like my TO30D) picks up considerably more hum simply due to its orientation to the power transformer, so, shoe-horning a ‘tallish’ OT into your amp may cause it to pick up hum from the power transformer – not much of an upgrade. “The TO26’s 7K to 8 or 16 ohm rating makes it ideal for a pair of 6V6s as well as 3,500 ohm to 4 or 8 rating for 6L6/5881s. Notice you always have an 8 ohm option with both types of power tubes. An impedance switch could be wired (I use a blackface grounding switch) as a power tube type selector for an 8 ohm speaker to go between 6V6s and 6L6s. The TO26 will typically give slightly more output with 6V6s due to its more efficient low-loss core steel and will keep the bass clean longer for more perceived clean headroom. As it takes the most watts to reproduce the bass, you notice distortion there first, and since Fender-type amps are so bass heavy, you can quickly hit the wall with headroom, so a noticeable increase in clean bass response certainly feels like a more powerful amp with the TO26. It is kind of like you installed a new speaker with a larger ceramic magnet that is more efficient than the old speaker. The amp is a little louder and the bass a little tighter or cleaner.

“There seem to be a lot of 6L6-based 5E3 amps out there now to get a little clean headroom from a circuit normally not known for much of that. The TO26 is a good choice for that type of amp as it will fit typical available chassis and cabinets. It has extra long 12” topcoat leads ready to strip and solder. I would reckon it would handle up to about 30 watts before starting to saturate and compress – plenty of cathode-biased 6L6s. I find that the Heyboer paper stick-wound and interleaved output transformers with premium core steel and heavy core stacks have typically better clarity or definition than ‘stock’ OTs. Call it fidelity or whatever you want – just clearer distorted and complex tones and better separation of notes in chords, etc. I use the TO26 in the Allen Sweet Spot, Accomplice Jr. and Hot Fudge with Nuts amps with excellent results. All of these amps can use either 6V6 or 6L6 power tubes. You know how a 5F6-A or Super Reverb has that huge 4 bolt OT for a pair of 6L6s to get the maximum clean bottom end? That is sort of what the TO26’s OT is to a pair of 6V6s. It just doesn’t even come close to saturating.

When we informed Dave that we planned to run the Deluxe with 6L6/5881 power tubes as well as 6V6s, he recommended that we try the TO26 since it had been specifically designed for such applications. He also sent a smaller TO20 transformer, described as being designed with a wider 1-1/4′′ lamination “fat stack” that provides 60% additional core mass than typical ¾′′ stack units for improved performance. The TO20 is a direct replacement for Blues Jr. and Princeton Reverb amps, and also suitable for dual EL-84 amps with an 8 ohm load.

Mr. Valco also sent us a replacement 5E3 output transformer he had bought on sale from Clark Amplification a few years ago made for Mike Clark by Magnetics Components in Schiller Park, IL – a company that has been producing transformers since 1943, having been the primary supplier for Valco and various Gibson amps in the ’50s and ’60s. A call to the company revealed that ToneQuest ReportV12. N1. Nov. 20104the transformer Valco sent was essentially their replacement for a Deluxe Reverb, model #40-18002 without bell ends per Clark’s request. We also learned that the company offers a complete range of Classic Tone vintage power and output transformers, including a reverse-engineered clone of a ’55 Triad 5E3 output tranny, model #18022.

We also contacted Paul Patronete at Mercury and requested a ToneClone “brown Deluxe” output transformer, since Larry Cragg had provided them with specific measurements from original OT in Neil’s ’61 tweed Deluxe, confirming that it was indeed a ’61–’62 brown Deluxe tranny. With a total of 6 output transformers to listen to, we took the Deluxe to Jeff Bakos, who set up a rig on his bench that enabled us to clip in each transformer and very quickly switch back and forth between them as we played a guitar through the amp. Are we having fun yet? Here’s what we heard:

Lenco – An excellent authentic “vintage” vibe for those that prefer the classic, if somewhat murkier sound of a tweed amp being pushed, lots of sag in the low end and a jangly pop in the top. And “old,” rather “lo-fi” sound indicative of the ’50s era amps.

Magnetics Components Clark Deluxe 18002 – Similar to the Lenco, but stronger and more robust, with a prominent growling character and voice. Thick, wooly and willin’ with better treble presence and clear string definition then the Lenco, yet an entirely “vintage” character. This tranny is comparable to those found in Deluxe amps from the brown era through silverface. Excellent power, punchy and fat with exceptional clarity and tone.

Magnetic Components 5E3 Clone – Percussive and dynamic with a faster attack response than the Clark/Deluxe Reverb version, this transformer was reverse-engineered from an original ’55 Deluxe OT. IT imparts an intense, throaty tweed character with enhanced mid and treble presence, remarkable clarity, and an authentic vintage ’50s vocal tone with softer bass response and slightly less volume and power than the Deluxe 18002.

Allen/Heyboer TO20 – An interesting variation with a much more modern, percussive dynamic character. The sound was not as heavy and imposing in the vintage style, and with this transformer the Deluxe reminded us of the more refined sound of a Fender Princeton, with excellent dynamic punch for slide and Allen/Heyboer TO26 – As advertised, the low end held up loud and proud with very little sag and an audibly higher threshold of clean headroom, although beyond 6 on the volume control the Deluxe was still holding nothing back. Overall, this transformer imparts a cleaner, high fidelity tone with more clarity and stout bass response than a typical stock 5E3 transformer. An excellent choice for enhanced low-end and maximum volume.

Mercury Magnetics brown Deluxe – Immediately recognizable, the Mercury displayed a trademark sound that is smooth, exceptionally musical, warm and balanced. Sounding more “high fidelity” than the Lemco or Magnetic Components transformers, but still seductively unruly enough to get yer ya-ya’s out. Sweet, rich, detailed and sticky.

Now, you may be wondering why we would bother to audition so many output transformers…. How much difference can it make? Well, forty-odd years ago when someone rigged that old Stancor tranny in the Deluxe, the only choice available to most repair shops was whatever was on hand in the scrap pile. Today we can shape the tone and dynamic response of an amp with a variety of “vintage” or more modern, custom transformers that allow us to recapture the original sound and feel of the amp, or improve upon the original design. Why did Cesar Diaz install output transformers for a Twin Reverb in Stevie’s Super Reverb amps, and Bassman transformers in his Vibroverbs? Because the first thing that chokes and overwhelms a smaller output transformer are the bass frequencies, and Cesar wanted Stevie’s amps to produce a rock-solid, thundering low end that could handle his massive wound strings. The tone we’re celebrating with our ’59 Deluxe is quite the opposite…. The raucous sound of the amp teetering on the edge is the key to it’s exploding tone, but if you wanted to go in the opposite direction with more headroom and a tighter low end, transformers like the TO26 have been specifically designed for that purpose. We once replaced the output transformer in our Pro reverb with a bigger MercuryToneClone Bassman, and the Pro grained a tone of clean headroom and unyielding bottom. Wanna make it even harder still? Use a plug-in diode rectifier in place of the 5AR4 rectifier tube. No saggy britches now. As with so many choices we make in the Quest for tone, the final decision comes down to your mission and individual taste, and Jeff agreed that between the Heyboer TO26, both Magnetic Components trannies and the Mercury brown Deluxe, the question wasn’t which one was “best” – all four were exceptional, but different. Some players would prefer one over another for different reasons described here, but all of them represent stellar examples of just how far we’ve come since the day that old Stancor tranny was used to put the Two Fifty Nine back into service.

One last detail needed to be addressed…. Could we safely run the Deluxe with 5881s or 6L6s if we preferred that sound over 6V6s? Once again, we asked the prescient Mr. Valco for some Hoosier insight:

“The impedance mismatch in this particular amp using the 6L6s is really not a big concern, it won’t hurt the amp and will either sound good or it won’t. The 6L6s draw 1.8 amps and two 6V6s draw 0.9 amp, so using the 6L6s will add about 1 amp more current draw that the power transformer needs to supply from the 6.3 volt heater windings. On some small 6V6 amps, using 6L6s can and does cause the power transformer to run hotter because more current equates to more heat. The concern is that the power transformer in the Deluxe, not being a large one to start with, has the extra 1 amp of heater current capacity to safely use the 6L6s. One way to determine if the power transformer is really stressed out with the 6L6s is to measure the AC heater voltage on pins 2 and 7 on the power tube sockets (or on the pilot lamp) and see if the AC voltage drops significantly from the reading using 6V6s versus 6L6s. It should be a bit over 6.3 volts AC with the 6V6 anyway (since the wall voltage is higher these days than in the early ’60s) and with the 6L6s you sure don’t want to see a large drop in voltage below 6.3 volts AC. If there is a large drop it means the transformer is having trouble supplying enough current for the 6L6 heaters if given enough time with the 6L6s could damage the power transformer. If the drop is only a few 10th of a volt, and doesn’t go below 6.3 AC, then it would indicate that the transformer is supplying the demand for the heater current and should be OK. Most Fender amps used power transformers that could handle some extra current demand.

And now we arrive at the moment of truth. We’ve been steadily reeling in a parade of new and classic amps for review in these pages for 12 years now this month – Marshall, Fender, Magnatone, Hiwatt, Vox, Valco, Silvertone, Ampeg, Gibson, Gretsch, Mesa Boogie, Park, Supro, Dickerson, Traynor, Budda, Western Auto, Standel, Dumble, Cornell, Clark, Crate, Divided by 132, Reeves, Bad Cat, Gabriel, Fuchs, Koch, Star, Category 5, 65 Amps, Balls, Bakos, Callaham, Blankenship, Reinhardt, Grammatico, Siegmund, Chicago Blues Box, Roccaforte, Headstrong, Rivera, Mad Professor, Talos, Maven Peal, Reverend, BC Audio, Savage, Goodsell, Fargen, Carol-Ann, DST, Two Rock, Germino, Matchless, Louis Electric, Swart, Demeter, Juke, Aiken, Bluetron, DeArmond, Carr, Victoria, and Dr. Z, with more coming. Lots of amplifiers, multiple models from the same builders, and among the foremost classics – Fender, Marshall, Vox, Hiwatt, Gibson, Ampeg and the entire Valco catalog, we have acquired, optimized and restored dozens of amps considered to be among the most desirable vintage models ever built. In the 20 watt wheelhouse occupied by the Two Fifty Nine, it has no equal by a mile. Game over.

After a lot of back and forth testing with different sets of output tubes, we became hooked on the thundering sound produced by a pair of Philips small-bottle 6L6WGBs. Thanks to Larry Pogreba’s talent for scavenging rare tubes (in Montana, no less), we are flush with several outstanding and stout pairs of RCA 6L6s, but the brighter Philips really lit up the Deluxe with a fresh and lively attitude that mirrors the bounce of a newer amp. With the ’64 Jensen C12N loaded, the Deluxe spookily nails the tones of Neil Young’s rig on Ragged Glory – a “studio” recording cut live with the Deluxe and Old Black in a barn on Young’s ranch with Crazy Horse. With the volume backed off to 4-5 a bluesy jangle emerges anchored by solid low end, rich midrange, the sweetest treble tones imaginable, and variable levels of sustain and edgy distortion that can be controlled both by the volume on the guitar and pick attack. The Deluxe does not discriminate between single coils or humbuckers, ravaging both with equal fervor, and the responsive dynamic character of this amp simply is not of this world. Rotating the single tone control sharpens treble without dumping lows or mids, while also subtlety increasing gain, as if you were using a boost pedal. A “Y” cord plugged into the Instrument and Microphone inputs enables the two channels to be mixed with great effect. As Neil Young described, bringing the mic input volume up with the instrument volume set between 6-8 gradually deepens the tone while slowly igniting an intense explosion of thicker second order harmonics and distortion as the dynamic character of the amp softens. Pushing the Instrument volume level up into the 8-12 range brings the volume up to a perceived level that exceeds 20 watts, while provoking an angry, pissed-off cascade of astonishingly rich musical distortion as the notes swerve into controlled harmonic feedback.

Switching from the Jensen to the Celestion transforms the Deluxe into the most stunningly toneful 20 watt Marshall you could possibly imagine. To be honest, you probably can’t imagine it, because we have never heard anything like this ourselves, even after owning a couple of vintage Marshall PA20s, a rare Lead & Bass head and 1×12 cabinet, and a Balls 2×12 18 watt. We could easily live with either speaker, and the Deluxe also just kills pushing our 8 ohm 4×12 pinstripe cabinet.

For those of you who appreciate a somewhat tamer vibe, we can assure you that the Deluxe loaded with a fine pair of 6V6s is equally mind-altering. The overall sound is a wee bit smaller in girth and less imposing, yet abundantly overflowing with vivid harmonic depth, a supremely touch-sensitive response, and brilliant combination of fidelity, clarity and bloom. Compared to a black or silverface Deluxe Reverb, the ’59 presents a more musically complex soundstage, less harsh, stiff and linear, and it lacks both the sharper treble of a blackface amp, and the scooped midrange character. The tone is rounder and meatier, the treble sweeter and less dominant, with an enhanced 3-D image.

Now, if you’re the type that skeptically requires a qualifier to add a stamp of legitimacy to such an over-the-top review, here it is, Mr. Been There-Done That…. The Deluxe doesn’t and won’t spew big clean tones at stage volume. Our ’58 Tremolux produces a cleaner tone with a higher threshold of clean headroom by far at comparable volume levels, and the taller tweed cabinet encourages a stronger, cleaner resonant bass and low mid response. The Tremolux is also equipped with a Mercury ToneClone Tremolux output transformer, which creates a tone that is less wooly, raucous and indistinct.

The busted-up sound of the Tremolux above 5–6 is gloriously righteous indeed, but with more clarity and less provocative intensity than the Deluxe. Taken in context, what we’re suggesting here is that in our experience, the Deluxe has no equal as both a Fender and Marshall style 20 watt rocker (depending on speaker selection), and we’ll add “blues” to that description equipped with 6V6s and the Jensen C12N. During our 2-month test period, we also routinely used our Lee Jackson Mr. Springgy reverb, Analogman-modded Boss DD3 digital delay, and a very cool, versatile (and cheap) Flip tube tremolo pedal reviewed here. Can a modern replica of the 5E3 Deluxe deliver the same inspiring tones as the Two Fifty Nine? The closest thing we’ve heard is the Louis Electric “Buster,” but no, magical happy accidents like this Deluxe can’t be reproduced today – and that is as it should and shall always be. Quest forth…

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In part I of our Marshall JTM-45 transformation process, we installed a point-to-point board from Metropoulos Amplification (www.metroamp.com) and began to hear the positive results of our test Marshall as it came to new life.

Now, in Part II of our continued Marshall JTM-45 transformation, we move forward with two additional changes in addition to having the opportunity to compare the final results to an original 1964 badge-logo Marshall JTM-45.  The two changes that we decided to perform were to swap out the stock output transformer to a Mercury Magnetics™ (www.MercuryMagnetics.com) Axiom® O45JT-C model as well as to upgrade the board’s capacitors to those made by SoZo Amplification. To say that we were excited as well as just plain curious about the final results, especially when we could now compare it to an original JTM-45 — is an understatement.

We contacted Paul Patronete at Mercury Magnetics™ and he hooked us up with the Axiom® output transformer. Paul added that the Axiom® O45JT-C is a custom version output using Teflon wire instead of the normal UL1015 vinyl wire. The Axiom® O45JT-C output offers 8 & 16 ohm secondary taps. When it comes to output transformers for the JTM45 amp, Mercury Magnetics™ offers a plethora of options beyond the stock, cloned, vintage replacement. Options available in the Axiom® line of output transformers are primaries optimized for KT66/6L6/5881 tubes or EL34/KT77 tubes. Secondaries with just about any output impedance combination that one could want. Many of these custom Axiom® models feature “mil-spec” Teflon wire leads with silver tinned, nineteen strands of high purity copper. All of the Axiom® transformers are hand wound from period correct specimen, vintage blueprints. One of the more popular Axiom® pieces that Mercury Magnetics™ offers is an exact clone of the highly coveted Radio Spares output transformer. The Radio Spares output is from the early original, first run Marshall JTM-45 production amplifiers. Mercury Magnetics™ offers several versions of the Radio Spares output. One of the most popular versions is a Teflon wire leaded version. The Radio Spares transformer is well-known for its association with the earliest Marshalls and according to Paul is what you’d find in the famous Eric Clapton “Bluesbreaker”-era amp.

Those that have listened to or played through a properly running Marshall JTM-45 know the sound. It’s a smooth and naturally compressed distorted tone that when pushed will provide just enough crunch to know it’s characteristically a Marshall, but without any of the “buzzing bees” preamp tones characteristic in high-gain preamp-gain emphasized amplifiers. As you push the volume controls up higher on a the best JTM-45s, it’s clearly the sound of rock with its fat bottom end, lovely harmonic overtones, and sustain that sits well with the best blues and classic rock tones heard. All of this packaged in an amp that really is one of the most dynamic and player-responsive amps ever built.

The reissue JTM-45, while certainly not a “bad” amplifier on its own, really does lack much of the detail and smoothness that is really much easier to grasp and identify when heard. For example, the reissue JTM-45 in stock form would thicken up appropriately with the expected tube compression when turned up, but it clearly was not as smooth. There are definitely some tones that sound a bit “grainy” and edgy that a properly running original JTM-45 doesn’t have.

A project such as this JTM-45 reissue transformation offers an exciting opportunity for those serious about maximizing their tone, but either don’t have or don’t want to shell out the prices for the originals. As of this writing in early 2004, script-logo JTM-45s are commanding a minimum of $4,000 and the better examples are going for more than that. Our badge logo JTM-45 featured here generously on loan for the story has a value that may well be approaching $10,000 by today’s estimates.

With that aside, we should start out by saying that this is not a thorough “apples-to-apples” comparison between the two amps. To be 100% fair, ALL the components would have to be altered to the exact specifications of our 1964 badge-logo Marshall JTM-45 and that really wasn’t the point. The point of these transformations was to get the stock reissue JTM-45 sounding more like the “real thing” as described above with regards to the powerful, smooth and dynamic Marshall tone.

Another issue beyond the component values is that we’ve opted to keep the power transformer in stock form for the time being in the JTM-45. As a result the transformers will supply a different amount of B+ current to the plates and so it will not respond in exactly the same way as the original Badge logo model.

One final, and perhaps most important point, which Mercury Magnetics™ vice-president Sergio Hamernik added: “The transformer in a 30-year old amplifier will sound characteristically different as it ages compared to a new replacement, even if the replacement is built with the same materials.” And while the component materials and manufacturing methods used by Mercury Magnetics™ are made to the exact same standards as the originals (Sergio also added “Every turn, every layer, is copied and blueprinted exactly, including any original manufacturing anomalies found during our rewinding process of the original, vintage specimen, Sergio emphasized that the ToneClone™ series transformer will still sound different, but “like the original did in the amp when it was new” and not like the tone of the aged 30-year-old transformer. Since much of our favorite tones were recorded at least 20 years ago, perhaps this isn’t such a bad thing?

Sergio did suggest breaking in the new Axiom® transformer with 20 to 40 hours of hard playing time. He also said that this break-in period will get the transformer about halfway there to that 30 year seasoned tonality. Thermal cycling and running magnetizing currents through the transformer (playing the amp) will definitely sweeten things up in that period of time.

We could and may still make further changes to the reissue JTM-45 in the future and report back. However, with the point-to-point board, reduced “vintage” filtering, and tube swap that we performed last time around, along with the planned replacement of the on-board capacitors and output transformer for this second round, we thought that we’d be in really good shape with the final tonal results of this amp. And for those that missed it previously, we had previously written about Mercury Magnetics™ output transformers used in a 50 watt Marshall and were very pleased with the results. We anticipated nothing but the same results with the change in the reissue JTM-45 this time as well.

So far our project amp has KT-66 power tubes, 32x32uf and 16x16uf filter caps and a Metro Amps point-to-point circuit board.  At this stage, we were very satisfied with the results.  We could have stopped here and had a real tone machine, but we wanted to see if we could get even closer with a few more changes. Sonically, the reissue at this point prior to the SoZo caps and output transformer change, did exhibit more of the growl and gain of the original, but it still wasn’t nearly as smooth or as dynamically punchy as the badge logo JTM-45 was.

Mike Mullen on testing the SoZo Caps

While waiting for our Mercury Magnetics™ output transformer, I read about some capacitors that created quite a buzz on the Plexi Palace vintage amp forum.  We found that SoZo Amplification was offering custom made capacitors aptly named “mustard caps”.  They are obviously mustard yellow but apparently these caps are also made to the same specifications as the yellow mustard capacitors which were originally found in tube amps from the 1960s and 1970s.  These little yellow jewels keep the foil thickness, polyester film dielectric and voltage ratings the same as the originals.  In addition to the material makeup of the capacitors they also share the same physical dimensions.  According to the SoZo Amplification website, the physical shape has a lot to do with the sound because it changes the slew rate.

The SoZo Mustard Cap is longer and thinner as compared to most high production caps readily available today.  The additional length results in a different signal delivery time, changing the harmonics of the capacitor and yields smooth, clear, thick lower-mids.  Polyester film was chosen because of its deeper tonal character and aluminum foil was chosen to exactly recreate the capacitor’s original sound and performance.  SoZo also chooses to use tin-coated pure copper leads, which SoZo claims aids in the retro mustard cap sound.

I promptly received the package containing five .022uF and three .1uF SoZo Mustard Caps and soldered them in.  In about thirty minutes all the caps were installed and I was ready to hear the results.

I flipped on the power, plugged in a Seth Lover-loaded Gibson Les Paul and let the KT-66’s warm for a few minutes.  Turning off standby, I decided to start with my best impression of Angus Young from AC/DC to entertain my neighbors. What I heard from my Celestion loaded 2×12 cabinet was clear, warm guitar tones that sounded ALIVE!  The tone of the amp was basically the same, but it was much clearer, richer and more complex than what I heard before.  I was very pleased with the improvement.

Anyone that is due for a cap job on his or her favorite amp should really give the SoZo “mustards” a try and change those along with the electrolytics while you’re already there.  I think the results are very satisfying and the cost runs about the same as a decent guitar cable.  The caps can be ordered direct from SoZoAmplification.com or from MetroAmp.com.  MetroAmp.com is offering these SoZo caps individually or they can be ordered with one of their point-to-point boards.

A final point is that SoZo amplification states that there is a break-in period for the capacitors and that the tone will actually improve and be at best form sonically sometime between 40 and 70 hours of use. While I’m not there yet as far as hours of use, I definitely like what I’m hearing so far!

Installation and listening to the Mercury Magnetics™ O45JT-C Output Transformer

The Axiom® 045JT-C output transformer is part of the Mercury Magnetics™ Axiom® ToneClone™ series, and is 100% hand wound in the USA by Mercury Magnetics™ at their factory in Southern California. Mercury Magnetics™ offers a number of transformer clones for JTM-45 amplifiers as Marshall used a few different suppliers during different times with its own JTM-45s originally. Some people may have a preference for the earliest transformer equipped in JTM-45s, which were those built by the Radio Spares company. According to Mercury Magnetics™, the Radio Spares output transformer has more “high-fidelity” characteristics in its tone. According to Paul at Mercury Magnetics™, their Radio Spares clone is a special, intricate transformer that produces a subsequently wider frequency response and in some ways mirrors other transformers in design such as the early famous Partridge units in the Hiwatts.

However with that said, there aren’t comparatively as many JTM-45s equipped with original Radio Spares output transformers so we went with the more commonly found transformers as found in later JTM-45s. When speaking with Paul, he also noted that the original, vintage “Radio Spares” equipped JTM45 amplifiers are highly sought after and can command big dollars in the musical marketplace. Perhaps we’ll experiment with one in the future to hear the differences for ourselves.

The installation of any output transformer, while seemingly “simple” (“hey there’s only a few wires right?”) should actually only be performed by either a professional technician or by an enthusiast with a minimum of Electronics 101 knowledge, including the ability to read schematic diagrams, an understanding voltages and polarity, etc. This is the advice directly from Mercury Magnetics™.

The transformer includes a wiring diagram sheet listing the color-coded primary and secondary wires, and these may not necessarily match the wiring in your amp. Mercury Magnetics™ also warns that installers put safety first, as there are literally hundreds of AC volts that can come off of the primary. A typical technician will charge 30 to 90 minutes of labor for the installation, which can average anywhere from $50 to $150.00. Prices and the time required to install an output transformer can vary from technician to technician.

*Installation tip: anyone planning to replace both the output transformer and circuit board may want to remove the old circuit board and output transformer first and then mount the new transformer.  Then you can install the point-to-point board and not have to mess with it later to get at the output transformer mounts.

After some time and with the transformer installed, it was time to play! But first, a few minutes with the badge-logo JTM-45….

Taking a Classic for a Test Drive

The original badge-logo Marshall JTM-45 is truly an example of a wonderfully responsive guitar amplifier.  In its best state, it can provide a range of tones that vary between the liquid and thicker lead tones of early Clapton, to the warmer side of the Marshall crunch a la AC/DC that we all know and love. The vintage badge-logo JTM-45, that we have the good fortune of borrowing courtesy of our good friend Woody (thank you!), had recently gone through a full check-up through southern California’s own Plexi Palace, so we knew that it was in fine form.

And it certainly sounds like it. No other Marshall seems to be as well suited to provide such a wide tonal range as well as being able to provide a feel with beautiful harmonics and compression as a JTM-45 circuit. The sense of dynamics that can be controlled with one’s technique was right on the money. This JTM-45 plain and simply is THE ultimate blues and rock amplifier.

It stings and bites as musically as one could imagine with a Fender Stratocaster using the bridge position pickup with the Marshall’s channels bridged and the volumes set at about 7. With the neck pickup, the tones are fluid and with a bit of a gain boost from a floor box could easily capture the full sustain similar to what a player like Eric Johnson would get. The power output on the amp is moderately high, but at the JTM’s power range, it really is a nice match against any solid-hitting drummer and the perfect club amp for small and mid-sized venues.

With a Gibson Les Paul in hand loaded with LegendaryTones.com’s current favorite Seymour Duncan Antiquities and running the badge-logo JTM-45 through a basket weave Marshall cabinet (NOT the cabinet photographed here which is an earlier pinstripe) with original 25 watt greenbacks, the tone of the bridge pickup was pure AC/DC circa “Powerage” when running the volumes at about 6. With the volumes set at 7, the added gain and thickness moved into “Highway to Hell” territory. Switching to the neck pickup provided a wallop of a fat tone that seemed like it could sustain for days. Think early Cream here.

Listening in on the reissue JTM-45

After that experience with the 1964 badge-logo JTM-45, part of me didn’t want to turn the amp off, but alas it was time to move to our modified reissue. Running the same controls (and in fact the same tubes were used and setup in both amps) and equipment, I started playing the reissue with the Strat first. The immediate first impression: the reissue JTM-45 felt great – the same feel of compression and control of the dynamics was there. And there was also a noticeable improvement between the circuit since the change of both the output transformer and SoZo caps. Besides having a bit more power and punch in the signal, these changes really seemed to smooth out the reissue JTM-45’s tone and were definitely much more pleasing to the ear.

But specifically what were the differences between the reissue and the original? Well, the modded reissue stood out with a bit more attack in the high frequencies. It’s definitely a bit of a brighter amp than the 1964 badge-logo, but not by a great deal and not bright in such a way as to be “piercing.”  The reissue JTM-45 could definitely mimic the original with a simple reduction of presence and treble controls and it did very well. Also, both SoZo Amplification and Mercury Magnetics™ told us that there is a break-in period for the parts to obtain their final adjusted tone. Again, for the SoZo caps, its 40-70 hours, and Mercury Magnetics™ stated the average break-in period should be a minimum of 20 hours of hard playing time with its transformers.

All said, we couldn’t wait that long nor did we have the time to play continuously to then report on the changes, but maybe we’ll add a brief report in the future after the break-in period.

When switching to the Les Paul with the newly transformed JTM-45, the same characteristic bold crunch with a warm full bottom end was evident. The modified reissue JTM-45 is definitely smooth when overdriven and power chords are a thrill to bash out in AC/DC style. Leads in both pickup positions of the Paul sang nicely. The neck position is always powerful with the JTM-45.

Final Thoughts….

In both amps, the feel, sustain, and tone was tremendous. The reissue in its current form has a little bit more of a faster attack, while the original badge has a bit more of a relaxed sag to it characteristically. It’s also a little bit darker. That said, we expected differences especially considering that each amp’s circuits are not identical. But what they do both share together is the original Marshall tone that we grew up on and know and love. And the fact that this tone can be captured without the need to hunt down a costly original is a nice thing for players indeed. There is something to having an original — it’s a testament to a wonderful period of musical history that NO reissue would ever be able to capture from that perspective. But at the same time, one thing that the reissue has going for it in its favor is the fact that most players would feel much more comfortable taking it out to a gig or the all-night jam. I would be a bit paranoid taking out the original personally.

It’s a shame that some of our greatest musical instruments, whether we’re talking about a ’59 Les Paul or an original Marshall amp, are so highly-valued in this day and age that it’s difficult to “enjoy” playing them. However, isn’t it a nice thing that companies such as those featured in this article are so passionate about their products and in finding ways to empower musicians with great tonal solutions today? I’ve said it before — we’re definitely living in times of a tonal renaissance with the options we have and the number of great instruments, effects, and amps that we have available to us.

And though some people may say that, “they don’t build them like they used to,” I would actually agree. In the case of these dedicated companies and people, I believe they’re in fact building them better than they used to with care and meticulous detail that may not have always been present back in the day.

Source: https://mercurymagnetics.com/pages/news/LegendaryTones/LegendaryTones-02.htm

With all of the money one can spend on an amplifier, be it boutique, reissue or just a good roadworthy unit there is one area that can be overlooked, the quality of the output transformer. It is essentially the final filter in your amp chassis from the tubes to the speaker, matching the two up so you can make music! Let’s talk with Sergio Hamernik and Paul Patronete of Mercury Magnetics™ to find out what we all need to know about this overlooked most integral part of getting the best overall tone from your rig.

MH: What services do you offer at Mercury Magnetics?

MM: We offer new hand-wound transformers and chokes. We also offer a rewinding service for vintage transformers. Mercury Magnetics™ can rewind a transformer back to its original specs. Founded in Southern California in 1954 and incorporated in 1968, Mercury Magnetics™ has built a solid reputation on superior quality, reliability and customer satisfaction.

Mercury Magnetics™ has the right combination of experience and a low overhead operation to meet specific requirements. Custom designs, quality assurance and safety standards are included as part of out total customer support with no-nonsense pricing that often beats out standard “off-the-shelf” components, while not being bound to their limitations. Mercury Magnetics™ has a long standing reputation for quality and reliability. These transformers are not built “offshore” or “south of the border,” they are 100% handmade in the USA and are backed by a money back tone satisfaction guarantee. Their line of Axiom® transformers are found in some of the finest and best-sounding modern production amps manufactured. We build transformers and maintain a high standard for tone in the tradition of our forefathers, making improvements that they would have made if they had access to today’s computer assisted designs and materials.

MH: To what degree of effort do you extend yourself when restoring a vintage transformer and how does it happen?

MM: We methodically unwind the vintage transformer by hand and document each wind detailing every anomaly and turn. We then rewind the transformer by hand so it will sound exactly as it did when it was brand new. The interior of the transformer is new and the exterior of the transformer is maintained so it will look like a vintage transformer and sound vintage as well. We attempt to use every piece of the original tranny that we can use. We DO NOT attempt to improve or alter the original tone or frequency response of the vintage transformer. Our rewinding service is more time consuming and can be more expensive than purchasing a new Axiom®transformer. However, with our attention to detail and experience the customer can be assured that their vintage transformer will look AND sound terrific! Professional musicians, technicians and studios regard our rewinding services as the best. For transformers, the core material suppliers’ industry sets a +/- 20% tolerance on characteristics like permeability to begin with, so most of the industry realizes that anything that’s an inductor or transformer has that kind of tolerance unless a particular manufacturer tightens the tolerance up. But when we were dealing with high speed stick winding methods of the ’50s and ’60s, they didn’t really have time to scrutinize each coil, because these coils were wound simultaneously. There could be six or ten coils being wound at the same time. For example, we’d find missing layers, or layers that had a different number of turns than what was specified. So what I did was blueprint a transformer, documenting every layer, the space between turns, the number of turns, type of wire, and in some cases oddball gauges and half sizes. I would also take measurements of dielectric constants, leakage reactance, and other characteristics to be able to clone a transformer. So we ended up providing a service where we would fully rewind and rebuild original vintage transformers. Imagine disassembling the laminations in a core, numbering each one and putting them back in the same sequence.

MH: Do you believe that an output transformer can decay and lose its tonality over time, and if so why?

MM: Absolutely. I’ve proven that point with some of my more cynical, high-end customers, and I did it in such a way that we took a Marshall JTM 45 or a Plexi, I forget which, but the amp had been in England for years and been brought over here. The owner thought that the tone had decayed over time, it seemed darker, lifeless, and the higher frequencies weren’t as pronounced. They removed the transformer, and all that I did was rebake it in an oven and drive out the moisture. We put the transformer back into the amp and it was pretty amazing; it became a lot brighter and more detailed from the upper midrange to the upper frequencies. I’m not recommending that anyone start baking their old transformers. What we do with our transformers to avoid that degradation process is use a resin process that hermetically seals the coils. We do it in a vacuum chamber in which the coils are impregnated with the resin material and then we bake it thoroughly. Because of this process, our transformers should way outlast older transformers, including those made today.

Transformers are still being made today with the same mindset, do it as cheaply as possible while offering the customer a decent value for the money. It’s correct for the required impedances and matches all of that, but the rest of the details have been omitted because they just don’t have the time and budget to do the longer process. Years of research led us to the conclusion that not every aspect of a vintage transformer needed to be copied. There were problems and limitations in their day, so why repeat them? We achieved better results by combining old and new technologies. Making the math work for the best tone characteristics together with improved consistency and longevity is the formula we chose to follow.

There are a lot of vintage amps today with transformers that are going bad simply because they have aged. The tonal quality of the amp is deteriorating along with the transformer. Paper and certain types of varnishes used in these transformers tend to have hygroscopic properties. Moisture is absorbed over time affecting the insulation system and increasing the chance for high voltage breakdowns. To make matters worse, the primary winding voltage is high enough to produce a corona effect whose ions help oxidize this insulation. Over time, reliability and tonality will suffer. Do you believe in transformer cancer?

MH: In conclusion tell us what you think makes you the best company to work with.

MM: Our customer service is second to none! Paul Patronete heads the Axiom® division. He is an accomplished guitarist and has an experienced ear for vintage tone. Paul is more than happy to help our customers find the exact transformer to fit their tonal needs. Our website is constantly being updated with vintage and modern transformer versions. We will probably always be 2 or 3 pages short of having all of the various models listed that people may be interested in. Of course, we can’t possibly list every one-off we’ve done. We offer modern, updated versions of many of the classic transformers. We have added impedance taps for many of the classic Fender transformers, which were never originally offered. Having a detailed transformer spec is only the beginning. Breaking down into fine details what materials and assembly techniques were used decades ago help us assure our customers an accurate reproduction of vintage tone. We have carefully selected the best of new and old technology to put performance and quality ahead of economy. Our transformers are hand wound and the cores are hand stacked. Some materials we fabricate in house and others, like our steel laminations, are custom ordered. Because we build them one at a time, Axiom® Mercury Vintage™ are only available in limited quantities.

There is an audible difference between a budget transformer and an Axiom® Mercury Vintage™!

A good output transformer should go beyond its job of impedance matching. An amplifier’s overall personality depends on it. A desirable output transformer’s distortion has more detail; the harmonics seem even and smooth. Played clean, the transformer should sound natural without harshness. Obviously within the boundaries of the authentic tone characteristic the player is seeking. Better said, we still can’t make an apple into an orange. The output transformer is pretty much the last tone filter in a series of components. Other factors like tube quality and speakers can play an important roll as well. Also if you were to look at an amplifier circuit as a modulated power supply, then the quality of a power transformer and choke, if a choke is used in the circuit, it also affects tonality. The ghost note phenomenon would be an example.

A lot of the people modifying Marshall amps don’t want their transformer to break up so easily when they really overdrive their amps, and they can have a custom transformer built that will handle gobs of gain and still hold it together. A boutique amp builder might come along and specify a particular classic transformer with a few improvements. It’s all passion, really, because this is not by nature a high-dollar, profitable business. In fact, the machines that we use to hand wind the Axiom® transformers are from the 1960s.

In the early ’80s there were dozens of companies doing what we do in this area, and now there are perhaps 3 or 4. It’s frustrating for most transformer makers to have a musician describe to them a desirable tonal characteristic when that can’t really be put on paper. You have to at least be able to see things from a musician’s perspective. Paul and I have a decent guitar and amp collection, and we try to stay abreast of what’s going on. And we also have a lot of walk-ins and a sound room, so people can bring their amps in and play and talk about what they want.

Most of the current transformer manufactures sell them cheap and dirty, their approach is cookie cutter, they offer an okay value for what you get, but they mainly use bottom of the barrel materials. Unfortunately, they are barely in the ballpark of what really needs to be done if someone is serious about getting a vintage tone. If you have an inductance bridge, a simple test is to measure the primary inductance on a vintage unit and then on a new transformer. You’ll find that the inductance on the new unit is usually less than half of the vintage transformer. There is no way that transformer can sound like the original, but if you aren’t interested in achieving the authentic sound of the past, then everything that’s out there today is all right. The devil is in the details, and there is no substitute for doing things by hand. Certain items for our transformers that I couldn’t source elsewhere, I learned to make here, because there just weren’t any other sources for them.

As you can see the people at Mercury Magnetics™ go to great lengths to make their transformers sound good and “correct,” not overbuilding them to prove a point. To get that tone back into your amp have your favorite repair shop get you a custom-wound output transformer from Mercury Magnetics™. We have only skimmed the surface here in this profile; the power transformer also makes a difference in the performance of your amplifier. Mercury Magnetics™also makes transformers and chokes which we will speak with Paul and Sergio about in the future. Until then check out their website at www.MercuryMagnetics.com and never stop learning about your tone!

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A few months back, we restores a 1960 Vox AC15 to it stellar sonic signature. But as with all vintage amps, you never know when something might go on the fritz!

We had just tightened the last screw and powered up the amp to unleash some ear candy when – major bummer – there was a noticeable loss of signal. After a diagnostic check, everything pointed to the output transformer. So it was off to Mercury Magnetics and the meticulous mind of its founder, Sergio Hamernik, to re-wind this 51-year-old piece of harmonic history back to spec.

VG: So… is it all over for this output transformer?

Sergio Hamernik: Well, it appears that it’s given up its ghost. A major bummer to say the least! Replacing a transformer in a guitar amp is a similar feat to heart surgery. But it’s NOT “All Over Now Baby Blue” because we’re going to fix it. And when we do, it’ll likely sound better than the original.

This output transformer is an original, from 1960. The late 1950s into the early 1960s was a transitional period for VOX. And one in which their transformers were known to have various failure rates, depending upon which batch ended up on the chassis.

In your case, someone from the original transformer company had the bright idea of using low-cost wax instead of a varnish dip. No doubt to save their six-pence. To be fair, most transformer companies back then were somewhat ignorant to the unique demand placed on transformers by the guitar amp builders. As a means to inhibit rust on the iron core and also to fortify the insulation of the windings, the industry standard is to dip and bake transformers in varnish, NOT wax. And you know what happens to wax when it heats up!

When we originally opened this amp up, there was wax all over the chassis that had to be scraped out.

There is some merit to using wax if the component doesn’t generate much heat above ambient temperatures. Output transformers do not generate much heat by them themselves. Especially when they’re working within their design specs – even with the amp cranked. But what the original transformer maker failed to take into consideration was all the tubes packed in there next to the transformers on a limited size chassis. As you might have already experienced when you try to pull a tube from a powered up amp – they do get really hot.

Class A amps run hot because they’re designed to run wide open, no matter where you’ve set the knobs. Now enclose this or any amp into a box and you have created an ideal environment for a large temperature rise above room temperature. You can practically see the wax dripping off the transformer.

Plus, VOX amps are notorious for getting hot inside the cabinet anyhow.

Yeah, but VOX wasn’t the only company that stuffed wax transformers into their hot boxes. As we discovered during the course of rebuilding transformers from old Dynaco, Sunn, Marantz, and a few others, they tried this idea and had their share of failures, too. Using wax as an insulator would never fly today because it’s is extremely flammable. Is there such a thing as a nonflammable wax candle? Today’s amps though are probably the safest they’ve ever been.

How long did this wax-period last?

A few years of trial-and-error seems to have put a stop to that practice. The interesting thing is that among the first VOX amps built they used Radiospares transformers. Radiospares were extremely well constructed, varnished and expensive for their day. VOX amps with these transformers are highly sought after (“pre-wax debacle era”). However, I don’t believe VOX ever intended on using Radiospares for anything but prototyping and the earliest short-run productions.

Back then Radiospares catalogs were essentially England/Europe’s equivalent of the American Allied/Radio Shack catalog stores. We’ve run across a few early AC30s that came with their full compliment of Radiospares transformers. If they had failed it was due in part by operator error and not the construction of the transformers themselves.

It seemed that shortly after the Radiospares era VOX began to solicit other transformer companies. An early one that comes to mind was Parmeko. Based upon our forensic investigations, Parmeko seems to have been a low-bidder – which was clear by their rather feeble attempt to copy the Radiospares. Also, the Parmeko output transformers were dumbed-down with cheap materials and short-cut winding methods. Their transformers were in no way even close to the Radiospares quality, as their lack of tonality proved.

The engineering of the original Radiospares designs and workmanship are highly respected by us. They’re extraordinary, and for that time they really raised the bar – as demonstrated by Eric Clapton’s sound on the “Blues Breaker” album – a JTM-45 Marshall using the same Radiospares transformers!

What time period are we talking about?

This was during the first year of production for VOX of these amplifiers.

So… the output transformer in this AC15, is that a Parmeko?

No. It’s definitely after Parmeko, which once again marks another transitional period in the company’s history. Soon after Parmeko, VOX found another transformer supplier, Woden, a former military supplier who bid low to get the VOX order. Your transformer shows all of the tell-tale signs of it being a Woden.

Woden had some problems with quality and consistency. So the performance of their amps varied from transformer batch-to-batch. I wouldn’t be surprised if Woden was behind the idea of changing their production run to wax the transformers. Many amp players and collectors are quite fond of these Woden-era amps.

The Beatles era marked another transition for VOX. From Woden to Haddon, and Haddon is generally what people recognize when they think of that Beatles sound. Haddon was another former military contractor, but a step UP in build quality and consistency and probably cost from the Wodens.

If I were to purchase a vintage AC30, for example, I would look for the ones with Haddon transformers, although I still prefer Radiospares because they consistently give that benchmark tone. When the Beatles and the British rock seen took off in the early ’60s, VOX grew into a big corporate thing. At that point the Haddons were becoming just too expensive – so enters another transition in their transformer suppliers – a lower-cost company called Albion.

Although VOX saved money with Albion, their transformers created an interesting and more aggressive new VOX tone. Sadly, right after the Albion era the company went to Thomas Organ and shifted over to solid-state circuitry. And as we all know those were a part of VOX’s darker years.

The Albions do have a small group of followers that really dig that sound. But when I’m thinking “VOX” I’m really talking about the goose bumps that the Beatles era gave me with the Haddons. George Harrison had no problem overdriving his VOX amps into that unmistakable jangle and sparkle tone. Nor did Brian May with his signature thick and creamy textured sound.

For the record we have cloned Radiospares, Parmeko, Woden, Haddon and Albion transformers from that era and make them available in our catalog.

Did this transformer die because the wax had melted away?

Probably not. This transformer lost its wax at least 40 years ago. But even that’s okay. I have built amps and prototypes in the past where I used unvarnished transformers and they performed just fine. The main purpose varnish or wax is basically to coat the iron core. Rust proofing it because the better the grade of iron the greater the chance for rust to settle in. London fog didn’t help things either. Actually the coil’s insulation itself doesn’t always depend upon the use of varnish. So your transformer probably led its life mostly free of the wax, and it still performed well.

So why did the transformer die?

Transformers are not apt to commit suicide… no matter how poorly one plays the guitar. Transformers in general are not subject to the effects of aging. Instead, they usually die at the hands of others.Consequently, it’s almost always some outside operating condition or an offending part.

There are a few exceptions though. These come from some well-known and liked amplifiers that over the years have fallen victim to self-destructing transformers. Time bombs of a sort stemming from historically problem-laden transformer designs. More often than not inadequate internal insulation systems. An amp that comes to mind is the first generation of Marshall Majors. Their power transformers would frequently fail from voltage breakdowns. These transformers were a bit oddball since they didn’t appear to follow the build methods of the Drake transformers which are found in the 50 and 100 watt amps of the same production era. Jim Kelly amps another oddity, they came with power transformers with screaming high B+ voltages and an output transformer built with no insulation other than the coating on the magnet wire itself! I believe these were made by the now defunct Time Magnetics.Even the transformers from AmpegB15s are frequent visitors/patients to our rewinding / restoration lab. Since these transformers are in cans, and extremely expensive to repair, most clients choose our ToneClone replacements as upgrades in tone and reliability over the stock transformers. It’s only a matter of time, depending on how many hours are clocked on these amps, before we get that phone call. We see firsthand the failures of transformers like these that are designed without enough insulation to survive the demands a guitar player can put on them.

So was it something else in the amp that’s making the transformer work harder or the wrong way?

For your particular transformer we’re going to take a series of photographs showing you the rewind/restoration process from beginning to end. In the first photos we’ll show how we received the transformer from you. Take a look at the view of the bottom of the transformer. Notice that there is a tiny, pin-sized burn mark on the outer-wrap of the winding. This bothers me. It looks similar to a bullet entry wound.

Transformers in general can withstand a lot of abuse. But if there is something making the transformer work harder or the wrong way, then something in its operating environment has changed or failed leading to a breakdown. First of all, we noticed fresh re-soldering on the outside of the transformer. The only soldering that should take place are the lead wires to the terminals. There are very fine wires underneath the outer wrap that may get damaged from a lingering soldering irons. We prefer that people keep their dick skinners away from any original solder joints on the transformer.

With regards to your particular transformer we can narrow the problem down into three categories of investigation:

1. The condition of the components that connect to the input of the transformer.

2. The parts and connections that connect to the output of the transformer.

3. The possibility of rough or mishandling of the transformer

Could the transformer have failed from a shorted tube?

Not likely. A shorted tube failure will create a different witness mark on the transformer. A shorted tube usually causes half of the primary winding to light up like the heating elements of a toaster. Scorching a larger section of the input coil. Your transformer does not show any signs of that type of failure. Remember you still had some audio coming out of your amp. You’d be hearing crickets instead if the primary winding was shorted or melted.

On the speaker side?

I have a tendency to believe that it’s a voltage breakdown due either to a lack of load (no speaker connected), broken connection, or some defect or damage done to the winding itself. Another bit of evidence of course is that your amplifier had partial output – it wasn’t completely dead quiet.

Based on how you described the amp sounding it leads me to believe that the failure will be isolated to a small spot on the primary winding as opposed to the coil being completely burned. And I wouldn’t be surprised if the output winding still looks like new. Amps that end their life with noisy output generally don’t suffer from current (short-circuit) related problems.

That’s exactly what I heard when I turned on the amp.

Sometimes if you catch it on time by turning the amp off ASAP you have a chance of saving the transformer. If not, the transformer will eventually fry itself.

So the transformer didn’t see a proper load on it.

It probably was exposed to some form of open or partially open load or a connection. Which will cause out-of-control voltage spikes/arcs to take place beyond what the transformer’s insulation system is designed to withstand. “Transformers Gone Wild” is not a DVD I would recommend. There are no girls in it!

We can restore the transformer to better-than-new condition. But if you don’t find, fix or replace the offending part or bad connection that took it out to begin with before you re-install your resurrected tranny, you may to blow it all over again.

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One of the common questions we receive here is, “How can I get my (fill in the blank with your favorite brand name) reissue amplifier to sound like the original?” Often times the question will contain additional information of what had been done already. “I’ve replaced the preamp and power tubes and gotten it biased, but it still sounds cold and brittle….”

My usual answer involves examining the guitarist’s rig by taking a “system” approach when looking for a particular tone. Often too much weight (i.e. blame!) is put on the amplifier, perhaps because it is the most electronically complex item in a typical signal chain. Countless times I’ve personally played with changes to an amplifier, whether modifying it, changing the tubes, etc. and still had poor results in overall tone! Now if you’ve got the wrong pickup or speakers for your needs, then obviously no change to an amp is going to help all that much….

But presuming all other areas of your guitar rig/system are covered, then let’s go back to the amp itself and talk about a particular upgrade that hasn’t gotten the attention it has deserved: the output transformer. In fact, dare I say that in many cases — for example a reissue amplifier — a change to a higher-quality output transformer will have a greater impact on improving the overall tone than playing with different brands of tubes. Essentially, if you’ve got the best tubes, or the worst tubes, but if your output transformer is a low-grade model, your tone will suffer no matter what you do.

“What the heck is the output transformer?,” you may ask. Well in layman’s terms, it’s the final connection in your tube amplifier that takes the signal from the tubes and transforms them into impedances and power suitable for your speakers. In further layman’s terms, it’s one of the big “metal blocks” that is attached to a typical tube amplifier’s chassis and is the connection link between your tubes and speakers. Most commonly, there are two large transformers in an amp — The other besides the output transformer is called the power transformer — that is the one that is responsible for taking the wall current and transforming it into the DC power used by your amplifier. While the power transformer is directly responsible for areas like supplying exactly how much voltage goes to your tubes and therefore can affect the response or “feel” of the amplifier, it is the output transformer that can dramatically affect the tone of your amplifier since audio signal is actually passing through it.

Like tubes, transformers can distort and color the sound, but in part because they are wired to an amplifier rather than just being “plug-in” devices, I feel they receive very little of the attention as to how much they can affect the tone. In fact, output transformers used to be thought of as simply items to be replaced when they failed. However, I can attest personally that in many instances a change in the output transformer to a quality unit as an upgrade can make a huge difference in tone — especially with those popular reissue Fender, Marshall, and Vox amps currently being made.

I recently was fortunate enough to try some units out made by Mercury Magnetics™ (www.MercuryMagnetics.com) with the idea being to install and listen to the various tones of some of their models of output transformers. The test-dummy amp used in the first case was a stock 1974 Marshall JMP 50 watt model 1987 Lead model — it had recently blown its output transformer after a tube had shorted a connection between two pins of the tube socket so it was the perfect candidate. The stock transformer still actually “worked” somewhat – but the power output was very low, probably about 1/5 of what the amp should have been producing.

Mercury Magnetics™ offers three choices for replacement 50 watt output transformers and I had the opportunity to try two of them. The units are part of the Axiom® or ToneClone™ series which are hand-built replicas of the original transformers used in the Marshalls of various eras. In addition to the Marshall replacement transformers, Mercury Magnetics™ also makes various other Axiom® models for classic Vox and Fender amplifiers in addition to other toneful amps such as Ampeg, Gibson, Hiwatt, and many others.

The models I tested were the Axiom® 050JM, a 50 watt output transformer model based on the earliest “plexi” Marshalls, and the Axiom® 050JM-SL, a similar model with the “Self-Leads” option. Both are priced at $150. The SL model differs from the standard 050JM in that it is made just like the earliest original plexi transformers were, where the solid copper core wire that is wrapped around inside the transformer continues outside of the transformer and is also the same wire used to connect to the tubes and impedance plug, etc. The solid-core copper SL wires outside of the transformer are covered by glass-cloth fabric material, just like that used on the original ‘60s models. Conventional transformers (including the non-SL version 050JM) use a different type of wire, often Teflon, that is spliced at the end of the solid-core wire that is then wrapped around the transformer inside. So what’s the big deal about the wire type? Oddly enough, it seems to really affect the tone of the output transformer — more on this in a moment.

Mercury Magnetics™ makes another model as well, the 050JM-M ($175), that is designed to be used in conjunction with modified Marshalls that require a beefier output transformer to better match up to the higher B+ plate voltages and other modifications or changes that run the amps harder. Since the ’74 JMP Marshall guinea pig was a stock model, I focused on the two plexi model variations, the 050JM and 050JM-SL.

The 050JM-SL was installed first. Since Marshalls sound best when run hard into power tube distortion, that’s exactly the listening environment I used. The head was run through a ’71 basketweave Marshall cabinet with G12M-25 greenbacks. The guitar was my trusty Les Paul Classic with a custom-specified Seymour Duncan Seth Lover PAF-type pickup. The tone of the amplifier with the 050JM-SL installed was brighter in the upper mids as well as the highs. The gain was a bit lower than with the stock Marshall’s output transformer (when it was properly functioning), but the clarity of notes and chords was definitely improved. The 050JM-SL is a good fit for players that like classic-rock and blues tones and perhaps need a bit more high-end cut through the mix. Usually additional highs are the last things that are needed with Marshalls, especially the amps and cabs made from about the mid ‘70s onwards. However, if you play through an earlier model Marshall loaded into a basketweave cab with G12-25s, “over brightness” really is not an issue and the O50JM-SL is the right match for this earliest type plexi tone. If you’re running a later checkerboard cab and a ‘70s JMP Marshall like our test model, the O50JM-SL may prove to have a bit more top end than what you’d want.

Moving over to the O50JM, I was amazed at how different this transformer sounded, even though other than the lead wires that exited the transformer, it has the same specifications and parts as used in the O50JM-SL! After installing it, I knew that the O50JM was the choice for the hard-rockers, whether using a plexi or metal panel-front Marshall. The O50JM had more distortion dirt and grind in the tone. Both transformers contributed to a very smooth response from the Marshall, but the O50JM traded off the upper frequency and some of the clarity content found in the SL model for what sonically resulted to its increased distortion and compression.

I also had the opportunity to hear the difference in a 100 watt reissue Marshall SLP after a Mercury Magnetics™ O100JM ($250: their 100 watt “plexi” output model) was installed and the results were even more staggering than the difference between the stock and upgraded 1974 Marshall 50 watts. I attributed this directly to the obviously low-grade output transformer used in the reissue Marshall. Crank up a stock Marshall SLP reissue and the transformer really does mask the tone — bright, grainy and cold are the words that come to mind as well as a pure lack of fidelity. The O100JM brought back the low-end warmth, made the top end smooth and the famous Marshall midrange crunch was back in the equation just like the original models. This is tone, pure and simple — and the reissue SLP held its own against my original ’68 100 watt Plexi Marshall.

One area worth mentioning is that Mercury Magnetics™ can also rewind original vintage transformers if you don’t want to replace your burnt out original vintage transformer. Mercury Magnetics™ replaces the internal windings and necessary parts but uses the original core and covers and then puts the transformer back to original specifications. This is ideal for the person who is looking to maintain their amp in a form that is as original as possible. This service is more costly than simply replacing the output transformer outright, but it will also help maintain an amp’s value so it makes a viable choice.

When looking into swapping out an output transformer, while it’s not extremely complex to do, it’s best to have a qualified professional technician do the job as tube amps contain lethal voltages that are stored inside the amp even when it is not plugged in. It can be a bit of a time-consuming job as you have to get underneath the amplifier’s layout/circuit board so the average charge by a technician to remove and replace the old transformer with a new one will typically run about $100 or so.

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For decades, unquantifiable numbers of discussions have wrangled over the main ingredient of amplifier magic. Some amp gurus say it’s the vacuum tubes. Others swear by the capacitors. One question has always remained: Does the transformer have anything to do with an amp’s tone?

At Mercury Magnetics, founder Sergio Hamernik readily acknowledges transformers are a bit of anenigma. Nonetheless, he very firmly believes they are the true foundation of tone.

“They remain the biggest and most misunderstood black hole on the subject of amplifiers and tone,” he said. “But it’s really not all that mysterious. Get an amp’s magnetics right, and everything else falls into place.”

But what does a transformer really do? We recently spoke with Hamernik, posing that question along with a slough of others about the design, purpose, and effect on output “trannies” in guitar amps.

VG: How does a transformer affect the sound of an amp?

SH:A power transformer that’s underbuilt is much the same as an automobile with an under sized engine. Take two cars; one has a five-horsepower engine, the other has 500horsepower. Run them both to 70miles per hour. How long does it take the five-horse to get there?

In an amp, energy has to be converted into sound – and the quality of the transformer determines the quality of the rest of the amplifier. The better the power supply, the faster it will respond to the sonic demands of the player. It’s the amount of energy available; you don’t want to be waiting for the transformer to play catch-up with every note you pluck.

VG: A lot of players believe the main contributor to an amp’s tone are its vacuum tubes.

SH:Tubes are greatly influenced by the reactance of an output transformer and how it’s built. That’s why a Marshall amp sounds different than a Voxor a Fender. It’s the main reason why a Marshall has a distinct output transformer design. When you swap power tubes, the differences in tone are actually quite subtle. But if you replace the output transformer, you have a completely different-sounding amp.

VG: Does that mean some players put a little too much stake in“matched” output tubes?

SH:It’s partly true that you don’t need exactly matched tubes to get great tone. Often, you can get great tone with mismatched tubes if they’re at least operational. An old studio and touring trick was to swap power-tube positions, which often provoked the best tone. The trick was simply taking advantage of the differences in unmatched tubes!

So, while it’s important that tubes be tested for defects, they do not necessarily need to match. Tubes used for pre amp and phase splitters should, as a rule, be matched for balanced operation. The“imbalanced” concept is actually a fundamental design philosophy, noting differences between transformers built for hi-fi audio versus guitar tone.

VG: How’s that?

SH:Output transformers in amplifiers are highly reactive components. Not only are they reactive, they tend to be reactive in a lopsided way,which disturbs the tube into distorting in a manner we find pleasing for its musical qualities.

This introduces a key point; there’s a huge difference in design and execution between hi-fi and guitar amp transformer designs. In order for a guitar amp transformer to sound its best, certain imbalances must be built into its design. With hi-fi, you’re trying to get as clean and undoctored an output signal as you can, without distortion. The opposite characteristics –distortion, overdrive, “grind,” and“crunch” – are the cornerstone of what makes a guitar amp toneful. The term “clean” in a guitar amp actually means “less distorted,” but it’s still a distorted signal.

This reactive element of transformers running imbalanced is key to creating a complex soup we call ampli-fied guitar “tone.” When you’re making good soup, how thick or thin you cut the vegetables, the other ingredients you put in, all affect the flavor. The ingredients are often subjective, but in the end, the effort and attention to detail make all the difference.

Musicians were on the verge of losing the quality of their tone until some-body stepped in to utilize these fundamental principles. At Mercury, we made it out mission to gain the knowledge and craft of how to make guitar amp transformers.

VG: Do they still make transformers like they used to?

SH:No, with Mercury being one of the few exceptions. Consider the quality of the wonderful transformers of the 1950sand early ’60s, when manufacturers were still building to military specifications.

How could this happen. Well, transformers have always been the most expensive parts of an amp, somewhere around 50 percent of the costs. Not to mention they’re often heavy, which affects ship-ping costs. The folks responsible for purchasing face a lot of pressure to get costs down, thus maintaining the trend toward low-budget transformers. So it was inevitable that the “baby” – in this case, tone – got tossed out with the bath water.

Older transformers were designed to meet a power ratio of 6:1, 7:1, or even 8:1, the ratio meaning the power supply rating versus audio output rating. It wasn’t unusual to find 600 watts of power supply on a 100-watt amp. Talk about headroom!By the ’70s, though, price points started having more influence on product than did design, and power ratios started to slim down. Case in point; a popular line of amplifiers that made their mark in the ’60swere built requiring power ratios of 6:1 or8:1. By the ’80s they were dropped to 4:1,3:1, or even 2:1. Today a lot of transformers coming out of Asia are as low as 1.5:1!

Why is this important? Two main reasons; the first is that note separation and the amp’s punch-through characteristics depend on these ratios. The lower the ratio, the less dynamic and more dull-sounding the amp becomes. The second reason has to do with the operating temperature of the transformer. Many reissue amps have undersized transformers with low power-to-audio ratios. With as little as a half hour of play, many of these amps are running hotter than a bitch kitty.

Weak power supplies equate to weak sounding amplifiers. Understanding the relationship of magnetics to tone is the foundation of getting the tone thing right.

VG: Do transformers made with paper tube bobbins sound better than those with nylon?

SH:Paper bobbins will not rescue dull tone. Does wearing the right ball cap make you a better baseball player? Perhaps this myth started when someone compared a great-sounding vintage transformer that happened to have a paper bob-bin with a modern-day generic transformer with a nylon bobbin.

Paper tubes were a cost-cutting measure,first and foremost. They allowed a transformer manufacturer to easily wind more than one coil at a time. Back then, nylon bobbins were a high-priced alternative,but were recognized even then for superior performance.

Another problem plaguing paper bobbins are their sloppy tolerances, which make it difficult for any two transformers to sound the same. And paper tubes tend to collect moisture, which varies the reactive properties of transformer design, and thus,tone. We’ve proven this by taking transformers from highly humid environments and driving the moisture out of them. This procedure noticeably improved tone,brings back detail, and makes an amp sound less dull.

We have no bias one way or the other.Certainly, it would be less expensive to use paper. But we had some of the best studio players help us make the determination, and the choice was clear.

VG: How do you devise specs for transformers?

SH: We’ve been documenting designs for decades. Many include “happy accidents” and hidden treasure among the thousands of mediocre-sounding specimens. Our transformers are duplicates of those from the best-sounding amps in the world,many of which were literally one-of-a-kind designs donated by collectors and artists.

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I have always had a passion for music and audio. Guitar tone through an amplifier aroused my curiosity early on because many of the design rules for hi-fi equipment didn’t apply to producing great guitar tone. In the case of vacuum tube amplifiers, transformer design has a significant influence on the characteristics of tonality. Unfortunately, there is not a lot of reference material available and many of the original designers have either retired or passed away. In the early 1980s my partner and I purchased Mercury Magnetics, a transformer design and manufacturing company, from one of the early pioneers who founded this company in 1954. Our close proximity to the Los Angeles recording industry gave us access to studio technicians and many well-known musicians. Out of necessity, and to meet the demands of this level of clientele, we had to develop precise, “no compromise” methods of documentation and assembly techniques to rebuild and replicate these transformers to exacting specifications. A past example of this was when a legendary guitarist sought our services to help solve a frustrating problem. A technician had replaced the original output transformer in his amp with a generic copy, which resulted in completely changing the character of the amp. Several breakthrough albums from the late 1960s and early 1970s were recorded using this particular amplifier, and the sound of that amplifier really had helped define his signature tone. Needless to say, most musicians are very concerned about maintaining the character and unique tonality of their amplifiers. We ended up rebuilding his original output transformer and we provided two additional clones as backup.

TQR:Are you referring to all types of guitar amps, or more specifically British amps rather than, say, vintage Fenders?

I think that in all guitar amps, regardless of origin or brand, you also supplying custom transformers to amplifier manufacturers. Our extensive collection of vintage transformer designs really began to take off at that point in time. The ongoing accumulation of the finest sounding examples we could find inspired our line of ToneClone® transformers.

TQR: What is it about those particular transformers that make them so special, and how do you evaluate them? Do you install them in an amplifier and A/B them, or is it done more or less on paper?

We do have the necessary test equipment and software to check various parameters, but ultimately the ear has to make that decision. We also plug in, play, and conduct A/B testing at our facility. I have a dedicated sound room at home that has been tuned for the purpose of testing and evaluating audio equipment. We are lucky, because the Los Angeles area offers us an amazing amount of guitar playing talent that continues to help us maintain a level of objectivity. Also, some of our best listeners are avid tone enthusiasts who work in and for the local studios. These people understand good tone and give us their experienced opinions.

TQR:And can you describe what it is that makes these transformers special? What would we hear, specifically?

Having a detailed transformer spec is only the beginning. Breaking down into fine details what materials and assembly techniques were used decades ago helps us assure our customers an accurate reproduction of vintage tone. We have carefully selected the best of new and old technology to put performance and quality ahead of economy. Our transformers are hand-wound and the cores are hand stacked. Some materials we fabricate in house, and others, like our steel laminations, are custom ordered. Because we build them one at a time, the Axiom and ToneClone series are only available in limited quantities. Consequently, there is an audible difference between a budget transformer and an Axiom or ToneClone.

TQR:Can you describe the audible differences?

A good output transformer should go beyond its job of impedance matching, and an amplifier’s overall personality depends on it. A desirable output transformer’s distortion has more detail. The harmonics seem even and smooth. Played clean, the transformer should sound natural without harshness, obviously within the boundaries of the authentic tone characteristic the player is eeking. Better said, we still can’t make an apple into an orange.

TQR: What are some of the comments that you hear from players when they hear the Axiom or ToneClone transformers that you build? Is it a matter of touch dynamics, harmonics, all of that?

Yes, and let’s not forget musicians’ colorful tone speak, such as: The amplifier sounds more open, glassy, sweet, brown, fat, with more notes perceived. Barred chords are not muddy or squashed. Chimes and bell tones are much more apparent. Good note separation, sustain improved, more definition, etc…

TQR:And these things can all be affected by the output transformer in some considerable detail….

It is pretty much the last tone filter in a series of components. Other factors like tube quality and speakers can play an important roll as well. Also, if you were to look at an amplifier circuit as a modulated power supply, then the quality of a power transformer and choke, if a choke is used in the circuit, also affects tonality. The ghost note phenomenon would be an example.

TQR:Like a few amplifier builders we know, you have taken the direct route of precisely replicating the materials and tolerances that comprised the industry standard decades ago…

I remember having a conversation with Leo Fender a number of years ago and getting a chuckle out of him as he told me how amazed he was that so much scrutiny was being given to how things were done in the early days of Fender. He said that they had taken what they were doing in the ’50s and ’60s so matter of fact back then. They were hardly thinking at the time that they were building future classics. They were trying to make an affordable, good sounding, quality amplifier while still trying to make a buck. Leo also mentioned that for reasons of cash flow and/or inventory problems, they would resort to using alternate vendors from time to time. They kept a careful eye on cost of materials, and their supply, rather than hand picking components with alleged magical tonal qualities.

TQR:They weren’t matching tubes, either. All of this can and does get out of hand, but when your rig sounds so good that you can get lost in the magic of it, as a player, wonderful doors can be opened.

Years of research led us to the conclusion that not every aspect of a vintage transformer needed to be copied. There were problems and limitations in their day, so why repeat them? We achieved better results by combining old and new technologies. Making the math work for the best tone characteristics together with improved consistency and longevity is the formula we chose to follow. There are a lot of vintage amps today with transformers that are going bad simply because they have aged. The tonal quality of the amp is deteriorating along with the transformer. Paper and certain types of varnishes used in these transformers tend to have hygroscopic properties. Moisture is absorbed over time, affecting the insulation system and increasing the chance for high voltage breakdowns. To make matters worse, the primary winding voltage is high enough to produce a corona effect whose ions help oxidize this insulation. Over time, reliability and tonality will suffer. Do you believe in transformer cancer?

TQR:That leads us to an interesting situation in which the original output transformer in our ’60s Pro Reverb died, and we noticed how much better the amp sounded when we had installed a new transformer, which was a commonly available unit sold by MojoTone. Now, the amp sounded great before the old transformer went out, but it sounded significantly better with the new transformer. I asked our tech and advisory board member Jeff Bakos if it was possible for an output transformer to gradually decay over time, dying a slow death while you continue to lose ‘tone’ in a very subtle fashion over years of use. Is that possible? It seems as if that was the case with our amp, which we had always considered to have a rather legendary vibe.

Not only is it possible, it is probable. Keep in mind that if high voltage insulation breakdown has started, there is no reversing it. Assuming that the transformers insulation system is intact, we have in the past reversed some tonal degradation in original transformers under controlled laboratory conditions. I’ve proven that point with my more cynical, high-end customers. One example of this is an amp (a Marshall JTM 45 or a Plexi – I forget which) that had been used in England for years and then brought over to the United States. The owner felt that the tone had decayed over time, seeming darker, lifeless, and the higher frequencies were less pronounced. We asked him to remove the transformer and all we did when he brought it in was to re-bake it in an oven to drive out the moisture. We then vacuum impregnated the transformer with our proprietary resin to hermetically seal it before the final bake. He put the transformer back into the amp and the results were pretty amazing… it became a lot brighter and more detailed from the upper midrange to the upper frequencies. I’m not recommending that anyone start baking their old transformers, however….

TQR: No, but it seems to be a fair statement to say that it’s possible that your good sounding old amp might sound significantly better with a new output transformer. At least that was our experience, and in hindsight, we didn’t realize what we had been missing.

That’s true. The tonal degradation I’m speaking about is very slow and gradual. Your results would be even better if you had used ToneClone transformers. Any of our transformers should outlast older vintage transformers because each are put through the same process during production.

TQR:Doesn’t it become particularly more problematic with amps like AC30s and Hiwatts, where repro transformers have typically been poor compromises at best?

I believe that Marshall, Vox and Fender, to name a few, are doing an outstanding job of building affordable vintage reissue amplifiers. When an owner of one of these fine amps wants to take his/her tone to the next level, they will usually consult someone like a Don Butler (Toneman) for example. Don is an expert in the field of amplifier upgrades and the art of tonal improvement. Don is also one of the key figures in this mini industry, which is similar to the aftermarket for automobiles and motorcycles. Much like an engine tuner, Don will replace transformers and other components in the signal path to give the customer an upgraded, outstanding sounding amp that comes much closer to capturing the original tone they were seeking.

TQR:Your website seems to be very comprehensive, but can you be contacted over the telephone for customers that either don’t see their amp listed or perhaps have additional questions?

Yes! Paul Patronete, an accomplished guitarist who has a good ear for vintage tone and heads our MI division, is happy to help those customers when I am unavailable. Our website is constantly being updated with vintage and modern transformer versions. We will probably always be two or three pages short of having all of the various models listed that people may be interested in. Of course, we can’t possibly list every one-off we’ve done. Another cool thing we offer are modern, updated versions of many of the classic transformers. We have added output impedance taps for many of the classic Fender transformers, which were never originally offered. For any make of amplifier, we offer various mounting styles from the original. We can, in addition, alter tonal characteristics to fit the unique needs of each customer.

TQR:Are you building transformers for many small builders?

Yes. If you own a high end, small production amplifier, there is a chance you will find a Mercury Magnetics label on the transformers. Some exceptions are when certain amplifier manufacturers remove labels in an effort to keep us and other vendors a secret. We do maintain a confidentiality agreement with all of our customers if this is their desire.

TQR:Schumacher was a primary supplier to Fender during the tweed era, and they are still operating, although we understand that you generally have to be capable of placing a fairly large order to get geared up. That seems to be a significant barrier to many would-be amp builders.

That company is doing a good job of supplying inexpensive transformers to a high volume market. When a lot of emphasis is placed on meeting price points, something has to give. The cost of labor and materials are logically their first consideration. The end result is a compromise, and who could blame them? Ultimately, end users will determine if the resulting tone is adequate. Someone who has paid several thousand dollars of their hard earned money for a “high end” amp is expecting to have something that excites their senses along with a build quality that justifies their investment. This is where we can assist the amp builder. It goes beyond Mercury Magnetics “sending in the clones.” We have made every effort to break those barriers by eliminating minimum buy requirements. We work closely with today’s designers and builders to provide them with a thoughtful, next-level approach to their signature tonal requirements.

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Q: I have a 1993 Fender Blues Deluxe reissue and I love the tone but want just a little more clean headroom — maybe 50-60 watts instead of the 40 watts that the amp is rated at. I was wondering if it is possible to change the output transformer on this amp to give me an extra 10 watts or so? — Michael Cadó

A: Good question! The succinct answer is no, but there actually may be some benefit. Let me explain.

The output power of a tube amplifier is not totally determined by the output transformer, but also by the power, or mains transformer, and the voltage and current it supplies to the output tubes. The job of the output transformer is to take the power developed by the output tubes and convert it to a form that is usable by the speaker. The problem with replacing just the output transformer with a larger one is that there is simply no more power available from the power transformers and tubes to convert to more output.

However, occasionally there is a perceived increase in output when a larger output transformer is installed in an amplifier. To substantiate this, I contacted my friends Paul and Sergio at Mercury Magnetics, manufacturers of some very cool iron. Here’s what they had to say:

“By starting with the right transformer, or upgrading an inferior transformer, a player can get more out of the amp and experience extended clean-tone headroom and a noticeable presence of a bigger sound stage effect. Increasing an output transformer’s frequency and tonal capacity with more of the right kind of iron and copper will result in more inductance to the primary winding. It’s this inductance that has a profound effects on the tone and how large it sounds.”

In plain English, a larger and better quality output transformer will generally make an amp sound bigger, without actually having any additional output power. This is especially true with amplifiers that have output transformers designed to be just big enough to get the job done — a design theory that, I might add, is pretty foreign to us here at Budda. We believe in the concept of “bigger is better” and “size does matter.” (Ha, ha.)

The bottom line is you could have the output transformer in your Deluxe replaced with a larger capacity output transformer such as its big brother the Deville, or an even better upgrade transformers from Mercury, and hope that it achieves the results you desire. This modification, however, is not for the inexperienced as the PC board needs to be lifted and additional mounting holes drilled. Of course, you could go all the way and have the mains transformer replace with a Deville or upgraded transformer as well. This again is not for the inexperienced as the chassis cutout needs to be enlarged — but according to the original ’93-’94 schematics, the circuits are virtually identical, so you could have yourself a 60-watt amp in a 40-watt body, except for the 50-watt speaker.

Good luck, and have fun crusin’ with your new Deluxe Deville.

Source: https://mercurymagnetics.com/pages/news/PremierGuitar/PremierG-06.htm

You plug your prized mint-condition ’51 Fender Deluxe into the wall socket and crank it up. Next thing you know, you’re blown the transformer, the caps have puked, or you’ve toasted an original speaker. And you think to yourself, “Okay, the amp is 50 years old. It was bound to go sooner or later.” But maybe it wasn’t… an maybe age had nothing to do with it.

If you plug a vintage amplifier directly into a wall socket, chances are you’re not hearing what that amp sounded like back in the day. And that’s not because the amp is old and worn out; most old amps will run forever and sound great if treated well and maintained. But they don’t, because while that old amp may have sat in a closet for 50 years untouched, something else has changed over time — wall voltages.

Amplifiers from the 1940s, ’50s and ’60s were meant to run on 110 to 115 volts AC, while amps made in the ’70s are mostly rated at 117 volts. The back of an amp should indicate the wall voltage for which the amp is designed. The closer to new an amp is, the higher its optimal operating voltage. Depending on where you live, wall voltages fluctuate on a daily basis, and range from 100 to 130 volts! And that’s not taking into account the daily spies in power experienced on almost every line — power surges, transient voltage spikes, and of course that weird static sound that comes out of your amp, or the occasional radio station.

So, what does an extra 20 volts mean to a vintage amp? More bone-crushing power? More whump? Or is it a recipe for disaster? And is there anything you can do about that nasty static that sounds like you’re playing in Dr. Frankenstein’s lab?

Roy Blankenship, founder and president of Blankenship Amplification, recently sat down to offer some answers. Blankenship has worked as an amp repairman, production manager at Groove Tubes, and more recently — at the prodding of incessant customers — he began building a line of amplifiers. Today, he is one of the preeminent boutique builders (his Leeds 21 was one of the amps scrutinized in VG’s “5×18 = British Crunch Bliss” feature, December ’07).

* * *

VG: Is there a risk plugging a vintage amp meant to run on 110 volts into today’s standard 125- to 130-volt all current?

RB: Yes and no. Your power transformer doesn’t really care all that much, because all it’s doing is taking the voltage coming in and creating secondary voltages to send out. You’re probably not going to blow it by loading it with 20 to 30 more volts than it was rated for, depending on how much current is being drawn on the other side of it. Fortunately, most amps, like Fenders, had enough reserve built in that you will not be exceeding their specifications.

The problem is with an amp’s capacitors and filament voltages. The caps were rated for a certain value, usually about 450 volts. Most amps use 500-volt capacitors, so if you’ve got an old amp with original caps, you risk over-voltaging them. The collectors with pristine, all-original amps aren’t playing them, anyway. They sit in a closet or a glass case.

An amp’s electrolytics were designed for a shelf life of 15 to 20 years. So if you want to play your old amp — and you want it to sound good and not endanger your trannies — you need a cap job. Once you put new 500-volt caps in it, you’re going to be okay.

Some boutique makers now are doing what they call “voltage correction,” utilizing components so the amp will run at the original voltages. A certain percentage of my clients are concerned with authenticity, and this follows that vein.

The other thing you can do is just run the amp down a bit on a variac, which can accomplish a couple of things; it provides a safety margin, and lets the amp produce tube saturation at a lower volume.

VG: A lot of guys are using variacs to control output power, and your Variplex has one built in. Why the sudden boom?

RB: One of the original uses of a variac was as a diagnostic tool. When an amplifier is repaired, you turn it on using the variac starting at 0 volts. As you increase the voltage, the current draw on the “Amperes” meter (or ammeter) on the variac lets you know if there is a short within the amplifiers. On a tube amp with a tube rectifier, it’ll give an indication of current draw relating to the bias/voltage relationship. If your ammeter is slowly going through the roof, you have a bias problem. If you advance from 0 volts and the ammeter pegs itself, you have a shorted tranny, capacitor or power tube.

When Edward Van Halen came on the scene, he spoke of using a variac to alter his sound. Everyone wanted to sound like Eddie, so the variac became a fixture in a lot of people’s minds. While he initially claimed he increased the voltage on his amps, it was soon discovered he actually dropped the voltage to get his “brown” sound. Because musicians are so impressionable, I think it was a really bad idea to say this, because cranking an amp up to 140 volts can distress components to potential failure. As this information evolved, however, a lot of guys were discovering they could use the variac to reduce the line voltage, which causes an amp to break up sooner while otherwise retaining its sound.

Everybody knows that with tube amps, you’ve got to crank them to make them sound like they should. The sound of a guitar plugged straight into a naturally cranked up amp cannot be duplicated with a pedal. The variac allows you to get that same overdrive — that same touch sensitivity you get when the amp is dimed, but at a lower power level.

My friend, Bobby Carlos, who is a tech for Don Henley, uses a variac for small venues and says the amps sound fine down to 80 to 85 volts, then they lose integrity. When he was playing one of my amps with a Mercury tranny, he was down to 70 volts and it was hanging in there, illustrating that the quality of the transformer is also a consideration.

VG: Can a variac damage an amp if it’s running it at lower power?

RB: That’s a widely held belief, and one of those issues that does not have a simple answer. The problem is with the tubes, which were designed to operate on a 6.3-volt filament voltage. You can drop it some, but when you get too low, electron flow is disrupted; tubes work because of electron flow. So when you get below 80 or 85 volts, the amp sounds like crap. so that’s about as far adown as you can go in most situations.

Now, when you use a really robust transformer, you can take the amp down further. Mercury transformers make my amps work, in particular the Variplex, which stabilizes the filament voltage and varies the bias and the B+. Mercury trannies track perfectly as the variac is turned down — the sine wave on the oscilloscope does not change in character as you go from 60 watts to five watts.

I know people who’ve been using variacs for years and they’re still running the same tubers in their amps, and they still sound fine. My opinion is that you’re potentially going to have problems running the tubes down below 6.3 volts, but in the final analysis, when a preamp tube lasts 10,000 hours, if you get a sound that turns you on and makes you play, who cares if you have to replace a tube every 10,000 hours or so?

Some guys like running regulated filament supplies to make sure tube voltage stays at 6.3 volts, because that’s what the tube wants to see. Certain tubes may react differently to changes in the filament voltage.

VG: Will a variac work with every type of tube amp?

RB: It will, but the results will vary from amp to amp.

VG: What’s the best type of variac?

RB: Well, a variac is just a voltage regulator. It’s not a precision device. All it does is regulate the voltage from the wall to the amp’s power transformer. A decent one will probably run $50 to $75. Even the Chinese ones are reliable as long as you don’t drop them. What’s more important is that you have a good-quality multimeter, which is invaluable for maintaining gear and diagnosing problems. If you want to use a variac, it’s important to measure the actual output. Just because a variac says “110 volts” doesn’t mean that’s what is coming out. In my shop, it varies 5 to7 volts from what is indicated, sometimes dependent on the time of day. I did some measurements in a ’51 tweed Deluxe to give an idea of the differences between 110 volts and what comes out of the wall these days (see chart).

VG: What the “brown sound” the premise of the Variplex?

RB: We wanted to create a great-sounding amp that you could turn down to about 5 watts, so when you play a big room you have the power, but when you play a little room you’re not killing people in the first three rows. Really, we were trying to get a great Plexi Marshall sound, not a Van Halen sound.

Now, there are other ways to achieve distortion at lower volumes. Attenuators have become popular for achieving a cranked-up sound, as have master volumes and a process called “power scaling” invented by Kevin O’Connor. We liked the sound using the variac and chose that process. A master volume smashes your preamp tubes into square waves, but the power section really isn’t working. The great appeal of the variac is that the whole amp is balls-out no matter what volume it’s running. It sounds like a cranked amp, not an effect.

VG: What about all those awful static electricity sounds, especially with older amps that don’t have grounded cords, And also, radio signals. Is there any way to get rid of them?

RB: There are numerous devices that will get rid of what’s called electromagnetic interference (EMI), and radio frequency interference (RFI). These include ETA Systems, Furman, ART, Juice Goose, Tripplite, Atlas, etc. These companies specialize in products that “clean” electrical current. And there are some amplifiers that have an EMI/RFI filter in the AC input. And remember the old Acoustic 270? It had a little resistor/capacitor network on the output as an RF filter. Any of those I’ve seen that have been in some kind of city environment have burned out from too much “dirty” electricity.

A lot of times, radio signals through your amp means you have a grounding issue in the input section. It needs a ferrite core or a .1 capacitor to the chassis at the input jack. A lot of houses, especially older ones, will get rewired with three-prong plugs in the wall sockets, but they’re not grounded. There’s a circuit tester that tells you what’s going on just by plugging into the wall. They let you know if polarity is reversed, whether there’s a ground, etc. Sometimes, this can be a lifesaver. I know guys who have played clubs where one of these tools has saved them a lot of grief because they found out the club owner allowed the bouncer to come in and rewire the place. They would have gotten the shock of their lives if they’d plugged in and played.

Another solution is to call the power company and say, “I’m getting 130 volts out of the wall, and my light bulbs are lasting six weeks.” Sometimes they’ll send a guy to diagnose and help regulate it. We had big-time noise when we moved into the our building, and they came with some cool diagnostic equipment.

VG: What else?

RB: We should talk about old speakers. The formers (the round tube the voice coil is wound on) and the cones in old speakers are almost always dry-rotted and fractured. When you find that collectable old amp, be aware that the original speaker is going to expire within a few minutes when you crank it up. So it’s better to replace an original speaker and save it — and its original cone — for when some collector is going to pay you a fortune because the amp is all-original. You may get away with it for a while — but you’ve been warned! And luckily, there are many great re-coners out there.

VG: So, in summary….

RB: Remember that everything coming into and going out of an amp makes a difference in sound and quality of sound. A lot of guys don’t think about something as seemingly minor as electricity. But it makes a huge difference. And before you jump to a variac, you might want to get any old amp a tune-up. Sometimes just changing the caps and out-of-spec components can make a real difference in sound. The bottom line is finding a sound that turns you on and makes you play, because when you’re playing through an amp that really delivers, things come out of your fingers you didn’t even know were there!

David Jung is a professional writer/screenwriter and vintage guitar enthusiast living in Los Angeles, where he hangs with some of the best amp techs and collectors in town.

Source: https://mercurymagnetics.com/pages/news/VGmag/VGFeb08-RoyB.htm

Amp Transformers

Guitar amp articles

Amp Transformers, Output Transformers & Chokes

In late 2009 I had the opportunity to talk with Sergio Hamernik about the history of the Mercury Magnetics, how he became involved in making transformers for guitar amplifiers, and the difference a high quality transformer can make on your tone.

How did Mercury get its start?

The company’s roots date back to the early ’50s. Mercury was started by an old General Electrics transformer engineer who was working there pre-World War II. He then went on to do a bunch of design work for the war effort. And in the early ’50s, hung a shingle and became self-employed.

The name “Mercury” came out of his passion for Mercury cars, he always drove a Mercury since the late ’40s — he loved those cars — and eventually moved from the East Coast to the West Coast where he found that there was a lot of military and aerospace work. A booming economy in the early ’50s gave him a lot of business.

I met him in the 1970s when I was an engineering student and an audio enthusiast. Back then the electronics world was well into its solid-state “evolution,” and interest in tube gear was quickly disappearing. Not for me, however. I found myself in demand as a guy who knew about those “old things”; not only the math, formulas and specifications but I also had the “ears.” I could fix and keep the old gear running. So, I worked as a hired gun for a bunch of studio heads and pro musicians.

Typically when an amp’s output transformer blew. No one seemed to know any better so it was just swapped by whatever “factory” replacement or an off-the-shelf “equivalent” catalog transformer was handy. The invariable result was that the amp’s characteristic sound was gone. And no matter what resistors, caps or tubes were used, it could not be rescued or returned to its original sound. It was the transformers, it turned out, that were the key. The problem was coming up with a way to remedy the blown transformer replacement or repair that wouldn’t alter its tone.

To further complicate things, most transformer people I dealt with just didn’t want to bother with the music industry. For the most part the established electronics industry considered the needs and opinions of the audio and MI (Music Industry) communities as subjective, run by kooks, and occupied by people who didn’t know what they are doing. Audio and MI had always been considered the illegitimate stepchildren to the rest of the industry.

Out of pure necessity I had to got involved with transformer design and manufacture. As a customer of Mercury, they had built many custom transformers to my specifications — although we had many heated, on-going debates on the subject because the company owner hated audio! He never did understand what made guitar amp transformers tick, or how musicians thought and reacted to them.

That aside, he pestered me for almost a decade to take over the company because he felt I was the only one qualified. Eventually I did, and that was when Mercury got serious about the guitar amp connection. Sometimes you end up becoming an expert at something when no one else wants to do the job.

By the time I took the helm we were developing a really good and workable understanding of the relationship of transformer design to decent tone and how amps should behave. And around 1980 we began the long and arduous task of collecting and cataloging transformer specifications for every vintage amp, from all over the world. The deeper we dug, the more apparent it became that there were all kinds of factors that no one had previously suspected that affected guitar tone. And likewise, no one seemed to be paying attention to such things.

In turn, we invented proprietary technologies to aid this work. Even after three decades, we’re still innovating and discovering new things. From that fundamental research came our now famous ToneClone series, and later the Axiom line, which is probably the most significant advancement in toneful guitar amp transformer designs since the ’50s. Both product lines, we’re proud to say, have distinctly different niches in the annals of guitar amp tone.

We’ve not only cured the old transformer tone issues, but made it possible for musicians to upgrade their existing amps. And we’ve also made it possible for amp builders to reproduce amps of the same or better grade than even the most outstanding vintage amps of the past.

When did you become involved with making transformers for guitar amplifiers?

Back in the ’70s I worked for people on a one-to-one basis, usually under confidential arrangements, with certain rock stars that just didn’t want to be bothered by their names being flaunted around. What they want was their amps running right for recording, projects, touring, etc.

The problem was that when technicians would fix the amps they’d often loose their tone. It turned out that the culprit was the replaced output transformers. A changed output transformer would completely alter the character of the amplifier. So as I was the guy doing most of the work to resolve this issue, this expertise was brought to Mercury where we began a special division to cater to the guitar heroes.

Word got around rather quickly that Mercury was able to repair, rewind, and restore the original transformers and it just grew from there. The whole “Tone Clone” thing came from artists who had these amazing irreplaceable amps, amps that often made recording history. They didn’t want to take these amps on tour. So we came up with the innovative idea of cloning their original transformers that they’d fallen in love with. With the clones we could now easily make, for the first time ever, several identical amps for them. Or they would assign their techs to drop-in the cloned transformers so they would have, for example, six amps that would all sound the same as that first perfect amp.

These artists could now go on tour and not worry about breakdowns or theft, and keep their prized-originals back at home.

I worked with Ken Fisher, the whole Trainwreck thing, and a lot of the early boutique guys — and still do with Alexander Dumble. They preferred to keep things confidential and not let too many people know who their sources were because there were so few transformer designers that catered to the guitar amp market.

There was also a slow-but-steady dumbing-down occurring in audio and all that had been the post World War II momentum. Many of the ex-military components we’d been using were high tolerance parts, with mil-spec formulations of iron and copper and so on, that had been used to win the war effort. During the ’50s and ’60s we enjoyed the benefits of those high quality components at surplus prices. But by the late ’70s, and definitely in the ’80s, steel manufacturers started to change recipes to make the iron and other materials much more affordable.

You can hear the differences between a late ’60s Marshall, a late ’80s Marshall, and a Marshall today. A good listen will really help you to understand what changes took place. Unfortunately they made so many of those changes more out of economic considerations than anything else. The amps were loud but they seemed to be losing sight of the fact that their tone was disappearing — the “recipes” had been changed.

In addition to many other factors, the iron that Mercury uses is custom-formulated specifically for us. We buy enough of it to be able to dictate the exact recipe from the foundries. And all of our iron is literally from American ore processed right here in the USA. 100% American made to the original specs. Are there drawbacks? Well, some of the iron rusts more easily, but that’s actually a good thing because rust is a natural insulator. But the opposite is also true. When you see a modern transformer with a silvery or a shiny core just know that they aren’t worth a damn when it comes to tone.

Can you tell us more about guitar amp transformer history?

Here’s an amusing anecdote that may help explain our case for guitar amp transformers: There’s a great deal of documentation, from back in the mid-’50s, where engineers, and other technical people, were writing really scathing reports on how awful the transformers were in the audio industry. Those darn transformers! When tubes were plugged into them there was a tendency to distort! And they couldn’t have any of that! Likewise with harmonic distortion — especially even-order harmonic distortion.

Many amp builders, techs and players, today, don’t understand that tubes were originally designed to run dead clean, linear, and be efficient voltage amplifiers. That the tone we’ve all come to know and love is caused by the transformers literally “irritating” the tubes into distortion.

Which is, of course, the whole point of what we are looking for in guitar amps. Back in the ’50s, they were fighting to get rid of those nasty distortion tonal characteristics. Now we embrace them. But that was audio – guitar amps were still in they’re infancy and yet to be realized. It took a generation or two of innovative musicians to take those “undesirable” tonal characteristics and create music; to work with distortion and make it into something musical.

Ironically, it was that no-distortion engineering mindset that ushered in solid-state, and why it was so openly embraced in the ’60s. It was solid-state electronics that eliminated the output transformer.

In the late ’60s, Vox went to Thomas Organ to have solid-state amps built. They were very proud of this state-of-the-art amplifier. Curiously, I met a few of the musicians from the late ’60s that were sponsored by, and using, those amps. The tone was so awful and unbearable that they used the enclosures but hid their old tube gear inside! As you may already be aware, the vacuum tube industry is alive and well, and we’re still waiting for the solid-state industry to catch up.

Part of the confusion is that musicians assume it’s the tubes that give them their tone. There’s a lot of synergy going on in an amp, and the tubes certainly contribute, but let me illustrate this another way. Did you know that there is what we call “output transformer-less” amplifiers in the HiFi world?

These amps basically parallel a bunch of power tubes together until they get down to 16, 8, or 4 ohms. There is no output transformer, so you literally connect the speaker directly to the tubes. If you ever get the opportunity to do an audio demo with this style of amp, you will find that while it works, it sounds nearly solid-state. The output transformer is what provokes a tube into giving the characteristics that we find desirable as far as tone. Audio engineers didn’t want the tubes to distort, as tubes are basically nothing more than very clean voltage amplifiers. But when you have a reactive element like a transformer, you irritate the tubes into harmonic distortion.

Therefore, the difference between a good and mediocre transformer is based on how it works and syncs with these tubes to produce the kind of tone or distortion we are looking for. It is not as easy as winding some wire around a steel core, if it was then we would not be having this conversation.

How does a Mercury transformer made today compare to the transformers made in the golden age of amps (the ’50s and early ’60s)?

One of the biggest mistakes existing in today’s amplifier community, especially amongst hobbyists and do-it-yourselfers, is to blindly copy every aspect of a vintage amplifier hoping to get a piece of that golden tone. At best, this method still produces very random results. One of the key reasons for this is the often-overlooked missing transformer formula. A builder will fuss around with the tiniest of other details but completely miss how the transformers fit into the equation. In short, get the transformers right, then the rest is much easier. Here’s another look at theses deceptively simple devices:

For vintage-style transformers, Mercury starts by duplicating the transformer design, build errors and all. We use the best grade components like they did in the ’50s and ’60s. We wind every layer and every turn as if it were a circuit in itself. In fact, the diagram on the left shows an output transformer circuit equivalent. Most people would think it is an audio circuit. These things are fairly complex, and all the numbers have to be right in order to get the tone we want as musicians.

We really do follow the recipe to a point. Although we don’t repeat any of the mistakes or inconsistencies that were prevalent, but didn’t affect tone. For example, if you were into Fender tweeds or late-’60s Marshalls. To do this we would literally put the word out to rent or borrow dozens of amplifiers to find the one or two that had the sound, and dismiss the rest. There were typically many inconsistencies as well as “happy accidents” in the best-sounding examples we’ve auditioned. A lot of this has to do with the sloppy tolerances of the original transformers.

For our transformers we extract the best parts and virtues of the original best-of-breed transformers and remove all of the obstacles to tone. Perhaps just as important is that we adopted a “cost is no object” approach, making our transformers equal or better than the originals — and then add consistency. We now have this so finely tuned that if you bought a transformer from us five years ago, and then the same one today, it would sound exactly the same. You don’t want good batches and bad batches, which is precisely what made the original production runs vary so much.

Another issue is the so-called controversy between paper tubes and nylon bobbins. In the vintage years they used both. Some people think that somehow, some magical quality comes from using a paper tube winding form over a nylon bobbin. Tonally it made no difference at all. Paper tubes were widely out of tolerance most of the time because of how they were made. They would wind multiple coils on long sticks then use a saw or blade to cut off the various coils. In order for these long tubes or coils to come off of their winding forms they had to be conical. So this invariably meant that the first coil would be larger in diameter and the last coils smaller. As you can see, it’s easy to see why each of these inconsistently-made bobbins had a greater difference than the material they were made from. And there are other issues that occur over time, like paper has a tendency to disintegrate, collect moisture, etc.

When we switched to using nylon bobbins the tolerances were within 3,000’s of an inch of each other, as opposed to the wildly varying amounts found in paper tubes. If you were ever to take apart a really old transformer (pre-’70s) sometimes you’ll find wood wedges that are jammed between the paper tube and the core because that piece of paper was too wide and too sloppy to fit into the core correctly! They would force a wedge in there so the darn things wouldn’t rattle!

Which method, paper or nylon, made for the best tone? It’s the luck of the draw. We’re fortunate in that we have all these stars as clients who have these amazing-sounding amps. They went through the hassle of culling and choosing and picking the special amps that inspired them. The amps they recorded with. When we analyzed their transformers we sometimes found happy accidents or other little anomalies that would set a transformer apart from already sloppy tolerances of the standard production run.

There are little subtleties and changes from one transformer to another that make a heck of a difference tonally. So when you look online at our list of ToneClones, just know that they are from the hand-picked, best-of-the-best amps of their model and era. We continue this “weeding” process every day — and there’s apparently no end in sight. And that’s why, with some amps, we have several versions — each with its own tonal qualities — and others only a single set to choose from.

We use this process to establish new benchmarks. And you never know, tomorrow a new variant may arrive that totally blows away what we already thought was as good as it could ever get.

It is interesting that you take that approach to upgrading — the never-ending search for better-sounding benchmarks.

There is no real money or glamour in what we do, it is really all born of a passion for music. I come from a musical family, my Mom taught me as a little kid that music was a form of “food.” And that hasn’t changed. Everyone who works at Mercury is just in love with playing and listening to music, and we all believe that there is always some room for improvement or a way to raise the bar somehow.

Back in the ’70s and ’80s there wasn’t really a need for a company that designed and sold transformers to the public, so I stayed away from the general public for as long as I could and really only worked with professionals.

But at some point I realized that it was the average player who was getting ripped-off. Things were getting dumbed-down, the tone is slowly and steadily being vacuumed out of the amps. They were becoming duller-sounding, less interesting and more noisy. So, we decided to formally launch this product line so the average guy could have access to our technology. It takes an extreme amount of labor and effort it takes to build them to this standard. You know, even if someone wanted to buy 1000 transformers we would have to no-bid them because we really don’t have any way of doing things quickly.

Automation isn’t a practical solution. Everything we do is wound by hand, one at a time; it is the only way it can be done. Say you have 100 turns and 10 layers, well that would mean 10 turns per layer — that is how a machine would think of it. But what if a rock legend’s best transformer was 9 turns on one layer, 11 turns on the next, 7 on the next, 3 after that and so on, but the sum total ended up being 100 turns. Sometimes one layer can have a different winding style than the other; sometimes it is non-symmetrical meaning, if it is a push-pull, that one side of the primary doesn’t have the same turns as the other side. If that was the recipe that created the magic, we’d have to duplicate it. It’s just not practical to build machines to do that, so we end up having to do it by hand. It’s the proud old-school craftsmanship way of doing things. Something I think we could see a lot more these days.

We have a reputation for nailing tone. Our Fender transformers don’t sound like Marshalls, they sound like Fenders — and vice versa. In fact, we’ve become the industry’s new standard. If you were going to design or create a tube-based amp, it’s clear that we’re the folks to talk to.

Can you explain how a Mercury transformer can improve an amplifier’s tone and how they outperform the stock transformers found in most amplifiers?

In designing toneful transformers specifically for guitars (and that’s all we’re talking about here, not necessarily transformers for HiFi or any other purpose), the trick is in the magnetic field and how it behaves. The nature and the speed with which the iron reacts to the changing of an alternating current, in an alternating magnetic field, is what makes tone happen.

If you have “slow” iron, you’ll have a dull, non-sparkly sound with no bell tones — no matter what you do with the amp it will always be kind of noisy and fuzzy.

Where others have tried and failed they’ve blindly followed generic transformer formulas without understanding that guitar amps are different animals. They’ve somehow missed that point despite all the evidence to the contrary. The fact is that transformers for guitar amps do not necessarily follow textbook rules.

Indeed, it should probably be noted that we’ve developed a whole new technology around transformer design specifically, and only for the guitar industry. And that these designs are essentially irrelevant to any other use. But Mercury is also in a highly unusual position. Our decades of transformer “vivisection” have revealed all manner of unconventional tips ‘n tricks to us. And we’re now the keepers of this new, but proprietary, technology.

I seriously doubt that we could have done it without the, let’s call it “archeological benefits,” of our observations. Decades of studying the good, the bad and the ugly of guitar amp transformers have revealed a great deal.

Nothing that I have found in the reissue market, transformer-wise, even resembles anything that was made during the “the golden age of tone.” They are unrelated. The inductance, magnetic fields — all of that is just completely different and far removed from the original designs and recipes. So there is no way that a reissue amp is ever going to sound vintage unless they bother putting in the right ingredients.

With our Upgrade Kits, for example we’re trying to show people that we can move forward into new sonic territory from where vintage designs and tone left off. And our Axiom series transformers are the definitive showcase for this technology. Their tone is just amazing.

To push the point even further, we don’t include any “voodoo” parts in our Upgrade Kits. With the exception of the transformers, the Kits use only common, everyday, and off-the-shelf components. And most of our Kits also include a Mini-Choke. When the circuitry is correctly designed a Mini-Choke will make a huge improvement in an amp’s tone because, in terms of its power supply, it changes the way the amp works.

A good guitar amp is only as good as its power supply. If you have a dynamic and moving power supply that reacts to the demands of the audio end you’ll get get great note separation and good bass dynamics. You start to hear chimes and other phenomenon, and even the harmonics between the strings like a “5th note.” What the heck is the “5th note”? In barbershop quartets, if they get their harmonies right, they hear the “5th note” which is basically a harmonic of all four singers. We are doing that with our guitars thanks to distorted amplifiers.

Where did the idea for offering an Upgrade Kit for amplifiers like the Champ “600” and Valve Jr. come from and who designed the Upgrade?

I designed all of the magnetics (the transformers and Mini-Choke) and the general concept behind the Upgrade in league with Allen Cyr from the Amp Exchange. He is one of the most competent, finest amp designers I know of; there are only about five in the world that are true masters of the art — those who really know the math, how to read tone, how to listen to the subtleties of clean and overdriven sounds and tones, design circuits, and understand tube behaviors. As a bonus to those who appreciate this kind of thing, we always try to throw in some interesting tweaks and tricks that are unorthodox.

The idea is to spark some interest and perhaps get more people involved in tube-based amp tone and evolution. We expect some folks to study our Upgrade Kits, learn from what we’ve done, and take off into new territory from there. No one is offended by that.

But our initial concept was to take an inexpensive stock amplifier, one that cost no more than $100 or so, and modify it into a professional- or recording-quality amp for very few bucks. The Valve Jr. was the amp that gave us the inspiration for this project. Epiphone broke the mold with their little Valve Jr. amp. Out of the box it’s a remarkable value. So, although it was a bit of a challenge I thought it was interesting because we were not stepping on anyone’s toes — we were just taking something that already existed and designing an Upgrade Kit around it. A simple proof of concept that made the case of transformers and guitar tone. It just seemed like a cool thing to do. The project was validated when pro players began demo’ing our prototype amps — they couldn’t believe how amazingly great such a tiny amp could sound, it freaked them out, and they all wanted one of their own!

Our intention was to give the kid who was practicing guitar in his bedroom, whose parents are on a limited budget, REAL guitar tone. In a typical scenario, the parents buy a cheap little amp and guitar combo because they want to see if their kid will stick with it. But the kid doesn’t understand that the sound of the amp is fatiguing. He doesn’t understand why the amp doesn’t sound good. And he doesn’t realize that the amp is fighting him, tiring him out. I know that happened to me and so many of my friends when we were kids. Struggling with hard-to-play guitars and poor-sounding amps is probably the single-most reason so many budding young (and old) guitarists give up the pursuit of their dream. But some are rescued. One day they visit a guy, or hear someone play, who has the amp with the tone and with just the sweep a few chords they experience the “My gawd!!! I want to sound like this!” phenomenon.

That is what we’re trying to offer with these Upgrade Kits — where the tone is accessible to just about anyone. So they could have an amp that wasn’t dull or desensitized. An amp that allows them to make that real connection to the tone. Tone is not just about noise and volume, it is rather complex, and undeniably emotional.

At the LA Amp Show we had our Upgraded Fender Champion “600” running into a full Marshall stack. Here we had this little amp powering eight 12″ speakers and it sounded great. People kept asking to see the back of the amp thinking that we had somehow rigged up something, but it was just the little Champ “600” with our Upgrade Kit.

When you have a nice open tone it is not about counting watts because the window is so big and wide and the soundstage is so deep that it gives you the impression of more power. We are not putting out more power with the Upgraded “600” — but it sure sounds like it! It’s about opening up that tone window and giving you more.

It’s kind of like taking a radio whose volume is set to half way and having it placed about 20 feet away from you then bring it right next to your ear — the volume has not changed but you hear a lot more of its content.

One of the things we do when modifying a circuit is to lower the noise floor, which a lot of people overlook. Many amps, like the Valve Jr., have a nasty hum in standby. We had one that would just start to howl if you left it alone for a while! So whatever high noise floor it had would eventually feedback on itself and cause that noise.

Our focus is on inspiring people. We are trying to show people that they really can get great tone today, that there is no age that has come and gone. There is still a lot of fun things left to do with your amplifier when you are on the search for great tone.

Hearing how much these Kits improve upon the tone of the amplifiers, and how well thought-out they are, will a Mercury amplifier that is designed and built by you ever make an appearance?

No. We are a supplier of key components to the boutique industry and to several of the large amplifier companies, and that is a comfortable spot to be in.

There is no shortage of amplifier companies out there and it really is a conflict of interest if we were to start selling amps and transformers. I would rather stay out of it.

The whole point of the Upgrade Kits was an area where I didn’t see any conflict with the people who were in the amplifier business. In the end the Kits really represent a transformer demonstration. If you were to just show someone a picture of a transformer or even had one in your hand and tried to explain how much better their tone would be, no one would care — it’s a yawner. But when you build one of these inexpensive Upgrade Kits and you actually hear the difference that the transformers make, it really drives home our point that transformers are important, that they are the building blocks of guitar amp tone.

And in the end we do this because we love it, we really love what we do. We get to create all of these products that help people find their tone, and who wouldn’t what to do that?

Last month, we dropped off a toasted output transformer from a 1950 Vox AC15 with Sergio Hamernik and the team at Mercury Magnetics. From a suspicious pin-sized burn in the transformer’s outer paper insulation, they were able to determin probable causes for the transformers untimely demise. Then it was onto the rewind process! So, is it over for this amp’s output transformer?

VG: What goes into the process of rewinding a transformer?

We begin the restoration process with a thorough testing of the transformer’s electrical performance. Then we put the transformer’s insulation system through its paces – checking its integrity, making sure the voltages inside the transformer stay where they belong and not going wonky by arcing over to neighboring windings.

Consider these steps a weeding out process to find the proper candidates for restoration. If the transformer in question passes, then we return the transformer back to its owner or tech. Believe it or not, about 1-in-4 transformers we receive pass our testing! We offer free-of-charge transformer testing to anyone – all they have to do is cover the shipping costs. Some of these transformers are sent to us simply to make sure that all is operating well within specs – essentially for a second opinion.

We consider it a “sin,” a violation of our sense of professional ethics, to tamper with a perfectly good transformer. Rewinding or restoring transformers is a service born out of our passion for preserving tone at its highest standards. Properly rewinding transformers is a time-consuming and costly endeavor. The reality is that our rewinding service is not exactly a profit center. Who knows, maybe one day we’ll sober up and quit doing it altogether. But it does break our hearts when we find vintage transformers ruined by feeble attempts at rewinding by people who do not posses the necessary skills, or who do not have an interest in or knowledge of guitar tone.

If the transformer does fail our testing in any way, then we deem it unsafe to be put back in its amp. Now the process of rewinding begins. A large part of this process is akin to archaeology, or perhaps autopsy. We want to find out precisely how it was made and discover who or what killed it. So the first thing we do is remove the core stack and catalog each plate for original position and sequence. Check out the photo of your core completely apart and tagged. We did find some rust and will do our best to preserve it.

it. So the first thing we do is remove the core stack and catalog each plate for original position and sequence. Check out the photo of your core completely apart and tagged. We did find some rust and will do our best to preserve it.

We actually talked about that in an article we did back in the August 2009 issue of VG.

Yes that’s right. That patina of rust on the core of your transformer is an indicator of better quality iron that is ideally suited for guitar tone. The rust itself is working in league with the iron to assure that level of tonal performance. Modern day technology messes with the original iron processing recipes by adding rust inhibitors and other fillers. They’ve short-cut the more time-consuming and costly metallurgical processes – just like how auto makers are putting in more plastic than metal in their cars. Iron is an amazing magnetic conductor until it gets diluted or polluted with things that are better suited for non-audio applications. So if I had my choice, I’d prefer to play an amp with rusty transformers delivering the tone I want rather than an amp with pristine rust-free transformers that make the amp sound like it’s got a sock stuffed down its throat.

So the original core will go back in the transformer?

Yes. Since you have the right kind of iron core we’ll reassemble it the way we found it, then retune it to the original factory specs. If you were stuck with a transformer that had inferior core material, then we would suggest swapping it with Mercury upgrade iron.

It’s come to our attention that many current production transformers marked with “Made in the U.S.A.,” are actually using offshore materials, i.e. magnet wire and steel. More accurately they should read “Assembled in the U.S.A.” These self-defeating transformers are good candidates for our upgrades rather than rewinds.

Cores are the first component out and the last in during the course of restoration. An interesting fact: cores are never at fault when it comes to a transformer breakdown. The core is removed solely for us to gain access to the coil of the transformer. Taking apart the coil is a surgical process that begins our forensic investigation – like the crime shows on TV. Unpeeling a coil is quite revealing and will tell us the story of what happened. Under interrogation the coil always tell us the truth. A body of a man is wheeled in to the morgue. His wife insists that he shot himself while cleaning his gun – but the autopsy’s evidence proves otherwise. Now she’s under suspicion.

Well the coil of your transformer quickly spilled the beans. Remember that small black spot we noticed on the outer wrap of the coil? Sometimes there are innocuous blemishes in the form of spots that may appear on the surface of paper and are nothing to worry about. However, what we normally find in fried transformers is that the burn begins somewhere in the middle of the coil and works its way out – causing an exit wound. In your case the failure was not typical. Yours was an entry wound.

This is important because it indicated to us that it was killed by a sharp instrument that penetrated the outer insulation that broke through and severed two turns of the fine wire that make up ½ of your primary winding. Meaning that only one of the two power tubes was operational. The damage to the entire transformer was limited to that spot and only the very top layer of the magnet wire. Those broken wires were arcing across each other and taking advantage of the oxygen available from the perforation of the outer wrap to form that black spot. Further evidence to support these findings is the fact that the rest of the winding, all the way down to the bobbin, was unharmed.

This type of injury is caused by the usual suspects – the installer or remover of the transformer. The smoking gun possibilities are: the tip of a soldering iron, the tip of a Phillips screw driver… or rough handling (dropping or bumping the transformer against something sharp, etc.) with enough force to puncture it to cause such a failure. And finally, we cannot rule out beer as another possibility.

You can now relax. Your tubes and speaker are now ruled out as possible components of interest.

What gets burned out in a transformer that you’re actually replacing?

The magnet wire. When its insulation gets over taxed the fuster-cluck begins as the insulation system of the overall coil progressively losses its integrity (dielectric strength) and begins to arc or burn.

Can you ever rewind a transformer with its original wire?

We certainly wouldn’t do it. When the tires of your car are worn out, do you go out and buy used ones to replace them? Unless you’re a former stockbroker, what’s the point?

Magnet wire is not bare copper wire. There is a micro thin coating of plastic insulation that protects it from shorting. That very thin layer of plastic is susceptible to microscopic spider web-like cracking. And the process of unwinding the magnet wire virtually assures it’s going to get damaged.

Check out the photo of what the magnet wire from your transformer looks like after it was unwound. Does this look like something you’d want to put back in your transformer?

Has any of the machinery used for rewinding changed over the years?

Most of our methods and equipment for rewinding transformers we consider proprietary. So I’m going to stay away from specifics. However, the basic concept of winding equipment hasn’t really changed for over the last 100 years. Today, of course, we see more computerized machines. But we chose to stick with the gold standard of vintage equipment

Aside from ours, I’d be surprised if there is any precision equipment available that is dedicated for the sole purpose of unwinding/rewinding. Most attempts at rewinds today just use run-of-the-mill winding machines that produce, at best, haphazard results.

So if someone gives you a prized “mojo” tranny, do you have the capability of rewinding it exactly the way it was before?

You know I’m not a big believer in mojo. I maintain that all things to do with amps and their respective tone can be easily explained and reproduced, and dare I say it… improved. But yes, we do have the capability. We treat all transformers with the respect and the dignity they deserve. Most people in this business wouldn’t treat these transformers with such reverence. Likewise, they may not have any musical background or an appreciation for electric guitar tone. We’re more than just a transformer company. If the original transformer included magical “fairy dust” or whatever that made it sound unique and desirable, we wouldn’t overlook it or change anything. That’s our promise.

We must be doing something right because we receive mountains of mail, email and phone calls from players all over the world who thank us for giving back (or preserving) their amp’s mojo.

When you begin rewinding, are you using the same wire that was used in the ’50s and ’60s?

That brings up a couple of interesting and important points. First, Mercury is probably the only company in this industry that uses high-purity OFC (oxygen free copper) magnet wire made in here the U.S.A. – which we use exclusively because of its guitar tone (as well as our hi-fi audio) properties. This type of wire is clearly sonically superior and more consistent than the wire that was used in the ’50s and ’60s. Wire technology back then was limited to about half of the temperature and electrical performance of Mercury’s standards. As a result, transformers using our materials last longer, take more abuse, are sonically more revealing, and follow a closer musical path when over driven into harmonics.

The second point is that we, as players, would much prefer the original wire from the ’50s and ’60s to the offshore and south-of-the-border suppliers of magnet wire. We gave them a chance, thinking we’d save some dough for our customers. The tested results yielded dull tone, inconsistent batches with too many instances of insulation breakdowns. Not even up to the standards of the vintage wire. Further, in real life tests of putting amps through their paces, the sonic differences were quite noticeably inferior to the guitar players here at Mercury and the players working for the recording studios here in southern California.

Have you ever seen a negative effect of age on a transformer?

In some cases yes. Sometimes your ears may pick up on affects of transformer aging before you realize what is happening. Dark, dull and fuzzy tones with a general sense of lower output volume.

If anything suffers from aging it will most likely be core. There are two major contributors that cause a negative effect of aging and affect your tone. Before World War II the science of processing iron was not up to snuff. It seemed that it was difficult then to boil out residual carbon from the iron. We are carbon-based life forms that age. We also rely on carbon for dating or aging organic compounds. Even a miniscule amount of carbon left in the older iron causes it to age. As the iron core ages, the magnetic conductivity begins to poop out, slowing the transformer’s responsiveness with increasing losses. The result is less output with only lower mids breaking through.

During WWII there was a shortage of iron for the war effort. So many transformer companies, in order to survive the hard times, made their cores out of soup can sheet metal! Transformers made this way were naturally plagued the wrong kind of iron and harboring plenty of carbon to boot. Do not confuse iron with steel. Finally, when silicon was implemented to help force out the carbon from post war iron, transformer iron became much more stable. Stable enough to out last us all.

Another contributor to transformer aging comes from humidity. Amp owners who live in humid climates have noticed their tone changing over the years. This is especially true if their older amps had transformers built around paper tubes. Paper-bobbins have always run the risk of moisture absorption affecting and changing tone. Conversely, we found that amps built with premium transformers that utilize plastic bobbins weren’t likely to suffer tone degradation via moisture saturation. A couple excellent examples would be the original Partridge and Radiospares transformers from England. With all the fog and rain they experience, these transformers have held up quite well.

Maybe this explains why coating paper in wax was attempted early on? To verify that dew point (humidity) affected output transformer tone, we had transformers from amps made in the ’60s, that had never left the U.K., flown in. They were provided to us by some of the best legendary players their country had to offer. They knew what their amps sounded like originally.

We put their transformers (all with paper bobbins) through a dehumidifying process, then re-sealed them in a generous varnish dip and a full bake. All these guys freaked out and thanked us for giving them their original tone back! And one of the player’s even called with a personal thanks that we had reaffirmed that he had not actually suffered hearing loss! He said that as time passed he noticed less treble tones and a lot less note separation and definition. Note attacks seemed impeded. Other players also had this mistaken belief that their amps were getting too old to play.

Obviously this new transformer won’t be dipped in wax like some of the old experimental ones. What will you use to insulate it?

Well, I wouldn’t call your transformer new. It’s still a 1960. If we had restored a 1960 Corvette for you, does it change the year, make or model? Instead of a fresh coat of paint for the car, your transformer will receive a fresh dip of glorious varnish. A non-flammable sexy coat of see-through clear. Something that may last long enough to pass along to your grandkids.

What can I expect the tonal differences to be between the rewound transformer and the original?

It should sound as good as when it left the showroom floor in 1960.

Your only other option, as far as upgrading the tone, would be to try one of our ToneClones. These are copies taken from some of the finest specimen celebrity-owned and played “pick of the litter” amplifiers. And it’s likely that you’ve heard these transformers in action on your favorite recordings.

Have rewinds come back to you shortly after you’ve sent them out?

On occasion, yes. Installer error happens, and if you don’t find and fix the problem that caused the transformer to blow in the first place, you’re just setting yourself up for a repeat performance.

Another thing that’s fairly common is the use NOS tubes. Usually purchased from eBay. We had a situation once where a customer, after installing his rebuilt transformer, decided to re-tube his amp with 40-year-old American-built originals. As luck would have it one of the NOS tubes shorted and caused a different failure in the newly rebuilt output transformer.

Is a rewind in store for every old transformer, or will they go on forever?

No, not every old transformer will need to be rewound if taken care of properly. Perhaps most may outlast the “Iron Age” of guitar amplifiers which we’re living in now. The push for solid-state technology is tenacious enough to replace tubes/transformer-based amps in the long term (perhaps within the next 50 years?). Tubes may go but they’ll have to pry the transformers from my cold dead fingers before I’ll give them up.

We recently put transformers of all kinds, old and new, to the test by volunteering to help out the flood victims in Nashville. We offer to test and restore any flood damaged guitar amp transformer sent to us free of charge. We encountered some pretty nasty stuff. Yet, less than 5% of them needed to be rewound! (Namely, transformers with paper bobbin insulation, or amps that had been turned on before the transformers were tested.) Some of the transformers that came in were from amps that had been submerged in raw sewage for weeks! The odor was so fowl that we had to air them out, and the staff actually had to draw straws to determine who was going to work on them.

Talk about your shit jobs.

Man, you got that right! Ah, but there’s nothing like the fresh smell of varnish in the morning to help one deal with that challenge. We did manage to extract the moisture and reseal these transformers with varnish. The sacrifices you have to do to help out fellow musicians….

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In late 2009 I had the opportunity to talk with Sergio Hamernik about the history of the Mercury Magnetics, how he became involved in making transformers for guitar amplifiers, and the difference a high quality transformer can make on your tone.

How did Mercury get its start?

The company’s roots date back to the early ’50s. Mercury was started by an old General Electrics transformer engineer who was working there pre-World War II. He then went on to do a bunch of design work for the war effort. And in the early ’50s, hung a shingle and became self-employed.

The name “Mercury” came out of his passion for Mercury cars, he always drove a Mercury since the late ’40s — he loved those cars — and eventually moved from the East Coast to the West Coast where he found that there was a lot of military and aerospace work. A booming economy in the early ’50s gave him a lot of business.

I met him in the 1970s when I was an engineering student and an audio enthusiast. Back then the electronics world was well into its solid-state “evolution,” and interest in tube gear was quickly disappearing. Not for me, however. I found myself in demand as a guy who knew about those “old things”; not only the math, formulas and specifications but I also had the “ears.” I could fix and keep the old gear running. So, I worked as a hired gun for a bunch of studio heads and pro musicians.

Typically when an amp’s output transformer blew. No one seemed to know any better so it was just swapped by whatever “factory” replacement or an off-the-shelf “equivalent” catalog transformer was handy. The invariable result was that the amp’s characteristic sound was gone. And no matter what resistors, caps or tubes were used, it could not be rescued or returned to its original sound. It was the transformers, it turned out, that were the key. The problem was coming up with a way to remedy the blown transformer replacement or repair that wouldn’t alter its tone.

To further complicate things, most transformer people I dealt with just didn’t want to bother with the music industry. For the most part the established electronics industry considered the needs and opinions of the audio and MI (Music Industry) communities as subjective, run by kooks, and occupied by people who didn’t know what they are doing. Audio and MI had always been considered the illegitimate stepchildren to the rest of the industry.

Out of pure necessity I had to got involved with transformer design and manufacture. As a customer of Mercury, they had built many custom transformers to my specifications — although we had many heated, on-going debates on the subject because the company owner hated audio! He never did understand what made guitar amp transformers tick, or how musicians thought and reacted to them.

That aside, he pestered me for almost a decade to take over the company because he felt I was the only one qualified. Eventually I did, and that was when Mercury got serious about the guitar amp connection. Sometimes you end up becoming an expert at something when no one else wants to do the job.

By the time I took the helm we were developing a really good and workable understanding of the relationship of transformer design to decent tone and how amps should behave. And around 1980 we began the long and arduous task of collecting and cataloging transformer specifications for every vintage amp, from all over the world. The deeper we dug, the more apparent it became that there were all kinds of factors that no one had previously suspected that affected guitar tone. And likewise, no one seemed to be paying attention to such things.

In turn, we invented proprietary technologies to aid this work. Even after three decades, we’re still innovating and discovering new things. From that fundamental research came our now famous ToneClone series, and later the Axiom line, which is probably the most significant advancement in toneful guitar amptransformer designs since the ’50s. Both product lines, we’re proud to say, have distinctly different niches in the annals of guitar amp tone.

We’ve not only cured the old transformer tone issues, but made it possible for musicians to upgrade their existing amps. And we’ve also made it possible for amp builders to reproduce amps of the same or better grade than even the most outstanding vintage amps of the past.

When did you become involved with making transformers for guitar amplifiers?

Back in the ’70s I worked for people on a one-to-one basis, usually under confidential arrangements, with certain rock stars that just didn’t want to be bothered by their names being flaunted around. What they want was their amps running right for recording, projects, touring, etc.

The problem was that when technicians would fix the amps they’d often loose their tone. It turned out that the culprit was the replaced output transformers. A changed output transformer would completely alter the character of the amplifier. So as I was the guy doing most of the work to resolve this issue, this expertise was brought to Mercury where we began a special division to cater to the guitar heroes.

Word got around rather quickly that Mercury was able to repair, rewind, and restore the original transformers and it just grew from there. The whole “Tone Clone” thing came from artists who had these amazing irreplaceable amps, amps that often made recording history. They didn’t want to take these amps on tour. So we came up with the innovative idea of cloning their original transformers that they’d fallen in love with. With the clones we could now easily make, for the first time ever, several identical amps for them. Or they would assign their techs to drop-in the cloned transformers so they would have, for example, six amps that would all sound the same as that first perfect amp.

These artists could now go on tour and not worry about breakdowns or theft, and keep their prized-originals back at home.

I worked with Ken Fisher, the whole Trainwreck thing, and a lot of the early boutique guys — and still do with Alexander Dumble. They preferred to keep things confidential and not let too many people know who their sources were because there were so few transformer designers that catered to the guitar amp market.

There was also a slow-but-steady dumbing-down occurring in audio and all that had been the post World War II momentum. Many of the ex-military components we’d been using were high tolerance parts, with mil-spec formulations of iron and copper and so on, that had been used to win the war effort. During the ’50s and ’60s we enjoyed the benefits of those high quality components at surplus prices. But by the late ’70s, and definitely in the ’80s, steel manufacturers started to change recipes to make the iron and other materials much more affordable.

You can hear the differences between a late ’60s Marshall, a late ’80s Marshall, and a Marshall today. A good listen will really help you to understand what changes took place. Unfortunately they made so many of those changes more out of economic considerations than anything else. The amps were loud but they seemed to be losing sight of the fact that their tone was disappearing — the “recipes” had been changed.

In addition to many other factors, the iron that Mercury uses is custom-formulated specifically for us. We buy enough of it to be able to dictate the exact recipe from the foundries. And all of our iron is literally from American ore processed right here in the USA. 100% American madeto the original specs. Are there drawbacks? Well, some of the iron rusts more easily, but that’s actually a good thing because rust is a natural insulator. But the opposite is also true. When you see a modern transformer with a silvery or a shiny core just know that they aren’t worth a damn when it comes to tone.

Can you tell us more about guitar amp transformer history?

Here’s an amusing anecdote that may help explain our case for guitar amp transformers: There’s a great deal of documentation, from back in the mid-’50s, where engineers, and other technical people, were writing really scathing reports on how awful the transformers were in the audio industry. Those darn transformers! When tubes were plugged into them there was a tendency to distort! And they couldn’t have any of that! Likewise with harmonic distortion — especially even-order harmonic distortion.

Many amp builders, techs and players, today, don’t understand that tubes were originally designed to run dead clean, linear, and be efficient voltage amplifiers. That the tone we’ve all come to know and love is caused by the transformers literally “irritating” the tubes into distortion.

Which is, of course, the whole point of what we are looking for in guitar amps. Back in the ’50s, they were fighting to get rid of those nasty distortion tonal characteristics. Now we embrace them. But that was audio – guitar amps were still in they’re infancy and yet to be realized. It took a generation or two of innovative musicians to take those “undesirable” tonal characteristics and create music; to work with distortion and make it into something musical.

Ironically, it was that no-distortion engineering mindset that ushered in solid-state, and why it was so openly embraced in the ’60s. It was solid-state electronics that eliminated the output transformer.

In the late ’60s, Vox went to Thomas Organ to have solid-state amps built. They were very proud of this state-of-the-art amplifier. Curiously, I met a few of the musicians from the late ’60s that were sponsored by, and using, those amps. The tone was so awful and unbearable that they used the enclosures but hid their old tube gear inside! As you may already be aware, the vacuum tube industry is alive and well, and we’re still waiting for the solid-state industry to catch up.

Part of the confusion is that musicians assume it’s the tubes that give them their tone. There’s a lot of synergy going on in an amp, and the tubes certainly contribute, but let me illustrate this another way. Did you know that there is what we call “output transformer-less” amplifiers in the HiFi world?

These amps basically parallel a bunch of power tubes together until they get down to 16, 8, or 4 ohms. There is no output transformer, so you literally connect the speaker directly to the tubes. If you ever get the opportunity to do an audio demo with this style of amp, you will find that while it works, it sounds nearly solid-state. The output transformer is what provokes a tube into giving the characteristics that we find desirable as far as tone. Audio engineers didn’t want the tubes to distort, as tubes are basically nothing more than very clean voltage amplifiers. But when you have a reactive element like a transformer, you irritate the tubes into harmonic distortion.

Therefore, the difference between a good and mediocre transformer is based on how it works and syncs with these tubes to produce the kind of tone or distortion we are looking for. It is not as easy as winding some wire around a steel core, if it was then we would not be having this conversation.

How does a Mercurytransformer made today compare to the transformers made in the golden age of amps (the ’50s and early ’60s)?

One of the biggest mistakes existing in today’s amplifier community, especially amongst hobbyists and do-it-yourselfers, is to blindly copy every aspect of a vintage amplifier hoping to get a piece of that golden tone. At best, this method still produces very random results. One of the key reasons for this is the often-overlooked missing transformer formula. A builder will fuss around with the tiniest of other details but completely miss how the transformers fit into the equation. In short, get the transformers right, then the rest is much easier. Here’s another look at theses deceptively simple devices:

For vintage-style transformers, Mercury starts by duplicating the transformer design, build errors and all. We use the best grade components like they did in the ’50s and ’60s. We wind every layer and every turn as if it were a circuit in itself. In fact, the diagram on the left shows an output transformer circuit equivalent. Most people would think it is an audio circuit. These things are fairly complex, and all the numbers have to be right in order to get the tone we want as musicians.

We really do follow the recipe to a point. Although we don’t repeat any of the mistakes or inconsistencies that were prevalent, but didn’t affect tone. For example, if you were into Fender tweeds or late-’60s Marshalls. To do this we would literally put the word out to rent or borrow dozens of amplifiers to find the one or two that had thesound, and dismiss the rest. There were typically many inconsistencies as well as “happy accidents” in the best-sounding examples we’ve auditioned. A lot of this has to do with the sloppy tolerances of the original transformers.

For our transformers we extract the best parts and virtues of the original best-of-breed transformers and remove all of the obstacles to tone. Perhaps just as important is that we adopted a “cost is no object” approach, making our transformers equal or better than the originals — and then add consistency. We now have this so finely tuned that if you bought a transformer from us five years ago, and then the same one today, it would sound exactly the same. You don’t want good batches and bad batches, which is precisely what made the original production runs vary so much.

Another issue is the so-called controversy between paper tubes and nylon bobbins. In the vintage years they used both. Some people think that somehow, some magical quality comes from using a paper tube winding form over a nylon bobbin. Tonally it made no difference at all. Paper tubes were widely out of tolerance most of the time because of how they were made. They would wind multiple coils on long sticks then use a saw or blade to cut off the various coils. In order for these long tubes or coils to come off of their winding forms they had to be conical. So this invariably meant that the first coil would be larger in diameter and the last coils smaller. As you can see, it’s easy to see why each of these inconsistently-made bobbins had a greater difference than the material they were made from. And there are other issues that occur over time, like paper has a tendency to disintegrate, collect moisture, etc.

When we switched to using nylon bobbins the tolerances were within 3,000’s of an inch of each other, as opposed to the wildly varying amounts found in paper tubes. If you were ever to take apart a really old transformer (pre-’70s) sometimes you’ll find wood wedges that are jammed between the paper tube and the core because that piece of paper was too wide and too sloppy to fit into the core correctly! They would force a wedge in there so the darn things wouldn’t rattle!

Which method, paper or nylon, made for the best tone? It’s the luck of the draw. We’re fortunate in that we have all these stars as clients who have these amazing-sounding amps. They went through the hassle of culling and choosing and picking the special amps that inspired them. The amps they recorded with. When we analyzed their transformers we sometimes found happy accidents or other little anomalies that would set a transformer apart from already sloppy tolerances of the standard production run.

There are little subtleties and changes from one transformer to another that make a heck of a difference tonally. So when you look online at our list of ToneClones, just know that they are from the hand-picked, best-of-the-best amps of their model and era. We continue this “weeding” process every day — and there’s apparently no end in sight. And that’s why, with some amps, we have several versions — each with its own tonal qualities — and others only a single set to choose from.

We use this process to establish new benchmarks. And you never know, tomorrow a new variant may arrive that totally blows away what we already thought was as good as it could ever get.

It is interesting that you take that approach to upgrading — the never-ending search for better-sounding benchmarks.

There is no real money or glamour in what we do, it is really all born of a passion for music. I come from a musical family, my Mom taught me as a little kid that music was a form of “food.” And that hasn’t changed. Everyone who works at Mercury is just in love with playing and listening to music, and we all believe that there is always some room for improvement or a way to raise the bar somehow.

Back in the ’70s and ’80s there wasn’t really a need for a company that designed and sold transformers to the public, so I stayed away from the general public for as long as I could and really only worked with professionals.

But at some point I realized that it was the average player who was getting ripped-off. Things were getting dumbed-down, the tone is slowly and steadily being vacuumed out of the amps. They were becoming duller-sounding, less interesting and more noisy. So, we decided to formally launch this product line so the average guy could have access to our technology. It takes an extreme amount of labor and effort it takes to build them to this standard. You know, even if someone wanted to buy 1000 transformers we would have to no-bid them because we really don’t have any way of doing things quickly.

Automation isn’t a practical solution. Everything we do is wound by hand, one at a time; it is the only way it can be done. Say you have 100 turns and 10 layers, well that would mean 10 turns per layer — that is how a machine would think of it. But what if a rock legend’s best transformer was 9 turns on one layer, 11 turns on the next, 7 on the next, 3 after that and so on, but the sum total ended up being 100 turns. Sometimes one layer can have a different winding style than the other; sometimes it is non-symmetrical meaning, if it is a push-pull, that one side of the primary doesn’t have the same turns as the other side. If that was the recipe that created the magic, we’d have to duplicate it. It’s just not practical to build machines to do that, so we end up having to do it by hand. It’s the proud old-school craftsmanship way of doing things. Something I think we could see a lot more these days.

We have a reputation for nailing tone. Our Fender transformers don’t sound like Marshalls, they sound like Fenders — and vice versa. In fact, we’ve become the industry’s new standard. If you were going to design or create a tube-based amp, it’s clear that we’re the folks to talk to.

Can you explain how a Mercurytransformer can improve an amplifier’s tone and how they outperform the stock transformers found in most amplifiers?

In designing toneful transformers specifically for guitars (and that’s all we’re talking about here, not necessarily transformers for HiFi or any other purpose), the trick is in the magnetic field and how it behaves. The nature and the speed with which the iron reacts to the changing of an alternating current, in an alternating magnetic field, is what makes tone happen.

If you have “slow” iron, you’ll have a dull, non-sparkly sound with no bell tones — no matter what you do with the amp it will always be kind of noisy and fuzzy.

Where others have tried and failed they’ve blindly followed generic transformer formulas without understanding that guitar amps are different animals. They’ve somehow missed that point despite all the evidence to the contrary. The fact is that transformers for guitar amps do not necessarily follow textbook rules.

Indeed, it should probably be noted that we’ve developed a whole new technology around transformer design specifically, and only for the guitar industry. And that these designs are essentially irrelevant to any other use. But Mercury is also in a highly unusual position. Our decades of transformer “vivisection” have revealed all manner of unconventional tips ‘n tricks to us. And we’re now the keepers of this new, but proprietary, technology.

I seriously doubt that we could have done it without the, let’s call it “archeological benefits,” of our observations. Decades of studying the good, the bad and the ugly of guitar amp transformers have revealed a great deal.

Nothing that I have found in the reissue market, transformer-wise, even resembles anything that was made during the “the golden age of tone.” They are unrelated. The inductance, magnetic fields — all of that is just completely different and far removed from the original designs and recipes. So there is no way that a reissue amp is ever going to sound vintage unless they bother putting in the right ingredients.

With our Upgrade Kits, for example we’re trying to show people that we can move forward into new sonic territory from where vintage designs and tone left off. And our Axiom series transformers are the definitive showcase for this technology. Their tone is just amazing.

To push the point even further, we don’t include any “voodoo” parts in our Upgrade Kits. With the exception of the transformers, the Kits use only common, everyday, and off-the-shelf components. And most of our Kits also include a Mini-Choke. When the circuitry is correctly designed a Mini-Choke will make a huge improvement in an amp’s tone because, in terms of its power supply, it changes the way the amp works.

A good guitar amp is only as good as its power supply. If you have a dynamic and moving power supply that reacts to the demands of the audio end you’ll get get great note separation and good bass dynamics. You start to hear chimes and other phenomenon, and even the harmonics between the strings like a “5th note.” What the heck is the “5th note”? In barbershop quartets, if they get their harmonies right, they hear the “5th note” which is basically a harmonic of all four singers. We are doing that with our guitars thanks to distorted amplifiers.

Where did the idea for offering an Upgrade Kit for amplifiers like the Champ “600” and Valve Jr. come from and who designed the Upgrade?

I designed all of the magnetics (the transformersandMini-Choke) and the general concept behind the Upgrade in league with Allen Cyr from the Amp Exchange. He is one of the most competent, finest amp designers I know of; there are only about five in the world that are true masters of the art — those who really know the math, how to read tone, how to listen to the subtleties of clean and overdriven sounds and tones, design circuits, and understand tube behaviors. As a bonus to those who appreciate this kind of thing, we always try to throw in some interesting tweaks and tricks that are unorthodox.

The idea is to spark some interest and perhaps get more people involved in tube-based amp tone and evolution. We expect some folks to study our Upgrade Kits, learn from what we’ve done, and take off into new territory from there. No one is offended by that.

But our initial concept was to take an inexpensive stock amplifier, one that cost no more than $100 or so, and modify it into a professional- or recording-quality amp for very few bucks. The Valve Jr. was the amp that gave us the inspiration for this project. Epiphone broke the mold with their little Valve Jr. amp. Out of the box it’s a remarkable value. So, although it was a bit of a challenge I thought it was interesting because we were not stepping on anyone’s toes — we were just taking something that already existed and designing an Upgrade Kit around it. A simple proof of concept that made the case of transformers and guitar tone. It just seemed like a cool thing to do. The project was validated when pro players began demo’ing our prototype amps — they couldn’t believe how amazingly great such a tiny amp could sound, it freaked them out, and they all wanted one of their own!

Our intention was to give the kid who was practicing guitar in his bedroom, whose parents are on a limited budget, REAL guitar tone. In a typical scenario, the parents buy a cheap little amp and guitar combo because they want to see if their kid will stick with it. But the kid doesn’t understand that the sound of the amp is fatiguing. He doesn’t understand why the amp doesn’t sound good. And he doesn’t realize that the amp is fighting him, tiring him out. I know that happened to me and so many of my friends when we were kids. Struggling with hard-to-play guitars and poor-sounding amps is probably the single-most reason so many budding young (and old) guitarists give up the pursuit of their dream. But some are rescued. One day they visit a guy, or hear someone play, who has the amp with the tone and with just the sweep a few chords they experience the “My gawd!!! I want to sound like this!” phenomenon.

That is what we’re trying to offer with these Upgrade Kits — where thetone is accessible to just about anyone. So they could have an amp that wasn’t dull or desensitized. An amp that allows them to make that real connection to the tone. Tone is not just about noise and volume, it is rather complex, and undeniably emotional.

At the LA Amp Show we had our Upgraded Fender Champion “600” running into a full Marshall stack. Here we had this little amp powering eight 12″ speakers and it sounded great. People kept asking to see the back of the amp thinking that we had somehow rigged up something, but it was just the little Champ “600” with our Upgrade Kit.

When you have a nice open tone it is not about counting watts because the window is so big and wide and the soundstage is so deep that it gives you the impression of more power. We are not putting out more power with the Upgraded “600” — but it sure sounds like it! It’s about opening up that tone window and giving you more.

It’s kind of like taking a radio whose volume is set to half way and having it placed about 20 feet away from you then bring it right next to your ear — the volume has not changed but you hear a lot more of its content.

One of the things we do when modifying a circuit is to lower the noise floor, which a lot of people overlook. Many amps, like the Valve Jr., have a nasty hum in standby. We had one that would just start to howl if you left it alone for a while! So whatever high noise floor it had would eventually feedback on itself and cause that noise.

Our focus is on inspiring people. We are trying to show people that they really can get great tone today, that there is no age that has come and gone. There is still a lot of fun things left to do with your amplifier when you are on the search for great tone.

Hearing how much these Kits improve upon the tone of the amplifiers, and how well thought-out they are, will a Mercury amplifier that is designed and built by you ever make an appearance?

No. We are a supplier of key components to the boutique industry and to several of the large amplifier companies, and that is a comfortable spot to be in.

There is no shortage of amplifier companies out there and it really is a conflict of interest if we were to start selling amps and transformers. I would rather stay out of it.

The whole point of the Upgrade Kits was an area where I didn’t see any conflict with the people who were in the amplifier business. In the end the Kits really represent a transformer demonstration. If you were to just show someone a picture of a transformer or even had one in your hand and tried to explain how much better their tone would be, no one would care — it’s a yawner. But when you build one of these inexpensive Upgrade Kits and you actually hear the difference that the transformers make, it really drives home our point that transformers are important, that they are the building blocks of guitar amp tone.

And in the end we do this because we love it, we really love what we do. We get to create all of these products that help people find their tone, and who wouldn’t what to do that?

Source: https://mercurymagnetics.com/pages/news/GuitarFixation/SHinterview/index.htm

It doesn’t take too much digging to find a laundry list of boutique amp builders using Mercury Magnetics transformers in their products. From Mojave Ampworks to Joe Morgan Amps to kits from MetroAmp, builders have found that Mercury knows their iron. While transformers rarely receive the same level of attention of NOS tubes, speakers, or even guitar cables, they are a major contributor to tone. Think about it—the power and output transformers are the start and end of the line with any amp.

Based in Chatsworth, California, Mercury Magnetics has been building transformers for close to 60 years. I recently had a chance to talk with Mercury’s Sergio Hamernik to dig deeper into their roots, find out what one can expect from upgrading their iron, and what sets Mercury apart. Prior to our conversation, I had the opportunity to witness the remarkable transformation of an Epiphone Valve Junior modified from stock to hot-rodded, using one of their transformer upgrade kits. Not only was it a noticeable upgrade, it was a revelation in just how important the role of quality iron in an amp is. But because it is the single most expensive part of any amp, it’s no wonder we see so many modern amp manufacturers skimp on the iron to keep costs down. Let’s see what the passionate, and often hilarious, Sergio has to say about his part of the business.

I’ve been seeing Mercury transformers in amps for at least a decade. When did you get into the amp scene?

This happens to be one of our most often asked questions. Even though Mercury Magnetics’ roots go all the way back to the early 1950s, there are guitar players who are only now discovering us. But if an industry insider like you has been aware of us for at least a decade, then I suppose it means I don’t need to lay off any of our sales and marketing staff.

I would attribute most of our lingering anonymity to the old days. Back then, most of our clients from the audio community preferred to keep us as a trade secret from their competitors and the press. The typical transformer-savvy amp builder also didn’t usually want to share the credit with us, or reveal what their “unique” technical advantage was regarding audio and tone. Consequently, we were asked to maintain a low profile and generic look for our transformers for quite some time. On occasion, a customer in the know will spot a small “MM” mark on a transformer from an older piece of gear, and ask if it’s a Mercury. Odds are that it is.

It was the guitar amp crowd that pushed us to go above ground. Now Mercury gives any electric guitar player or amp restorer a taste of what the pros were using, talking about in their studios, and amongst themselves. Many players have told us their amps increased in value when upgraded with Mercury transformers, and this became evident when insurance appraisers began to contact us for verification. However, it wasn’t until the mid-1980s when we began to market our services and various brands to guitar players.

For me personally, I got into the amp scene around the mid- to late 1970s. I just found it to be a nice way to relax from the strain of oversleeping.

Your website shows a large number of amp manufacturers you have replacement/upgraded transformers for. What are your best sellers and why?

There are so many different camps loyal to their particular amp brand, so it would be difficult to single out the best sellers. The best sellers are transitory and change from week to week because guitar amp players are a fickle bunch. That’s why we’ve built the world’s largest catalog of guitar amp transformers where nobody is left out.

But trends tend to follow their own dynamics. And the current worldwide trend seems toward smaller wattage amps—regardless of brand. Conversely, the 100-watt heads are not selling like they used to. Players are gigging with no more than 15 watts and a few pedals. Regardless of playing style, they’re doing just fine abiding by sound level restrictions and kicking ass with the tone we feel Mercury upgraded amps deliver.

These players really get the fact that an amp lacking in tone can’t be fixed with higher power or covered up with a gain mod. An amp that coughs out an asthmatic tone at 50 or 100 watts easily fatigues both music listeners and guitarists. But the audience will stay until the bar closes if the band plays well and sounds great—even with as little as a few watts going through the available PA system.

What can a guitarist expect to hear when upgrading their transformers in a newer amp?

An amp’s transformers are the most important component in determining the quality of amplified guitar tone. And it’s no coincidence that they’re the most expensive parts in an amplifier. Many of the newer amps just don’t have the same “overkill” factor with their transformers as the amps in the ’50s and ’60s. Why? Ignorance and a bean-counter mentality. What’s good for accounting isn’t necessarily good for tone from an amp. Sadly, the people making these decisions are probably not players themselves and don’t seem to realize the damage they’re doing to the industry.

It’s not unusual to find a current production amp with a power transformer running hotter than hell, even without cranking the amp all the way. Or having an undersized, cheaply built output transformer whose sphincter begins to tighten the moment the guitarist reaches for the amp’s volume knob. An amp built around anemic transformers yields only to dull, thin, noisy, fuzzy mids and mushy bass. That’s what makes your notes sound more like farts through a pillow. This overkill factor is probably the only edge that some of the vintage amps have over the newer amps.

We have made it our mission to duplicate the performance of the best original transformer designs of all time. In terms of amplified guitar tone history, these transformers represent the best ever produced. – Sergio Hamernik

Have you ever noticed how most newer amps often weigh less, sometimes a lot less, than the older ones? That’s usually the weight difference between the old and new transformer designs. There is a direct relationship between weight and having transformers that seem to stay cooler and “loaf around” with power to spare, until a player demands more from their amp. It’s like they are waiting around having a card game, waiting for the player to do something. The best vintage tone was born that way. Newer amp tone can be easily improved—if the builder follows some of the same ideas.

Upgrading with quality transformers gives a second chance to a new amp owner to make things right with their tone, by reclaiming that overkill factor. Assuming there are no issues with the amp’s circuitry like bad parts or worn out tubes, a guitarist should hear and feel improvements with the very first pluck of the guitar. They should expect to hear the notes more detailed with overtones, and a quicker and more immediate response to their playing. Clean notes will have less sonic collisions with noise and reveal more bell tones, chimes, etc.

When more distortion is required, the player will sense better control of crunch and when break-up begins to happen. The coughing and hacking that happens when a stock amp is pushed, will vanish with a transformer upgrade. It will be replaced with longer sustains and notes that reach farther. The amp will also sound closer and bigger than the power it puts out—and the bass notes will have a tighter, rounder bottom end. And when pushed, she will still be able to hold that quarter from dropping—no matter how tall her high heels—something most musicians are looking for.

It’s not uncommon for guitarists to report that it took a few weeks of playing to fully realize what they’ve gained in terms of harmonic richness. These players have typically played longer and felt more inspirational emotions sucking them in, as they have invested more time into relearning and becoming reacquainted with their amps.

Many players become very attached to the transformers in their vintage amps. When you create ToneClones or Radiospares and Partridge versions of these classic transformers, how close are they get to the originals?

Radiospares and Partridge are our brand specific clones, whereas ToneClones are “best-of-breed” duplicates culled from the hundreds of other brands that have made transformers over the years.

We have made it our mission to duplicate the performance of the best original transformer designs of all time. In terms of amplified guitar tone history, these transformers represent the best ever produced. In the grand scheme of tone pursuit, these designs are incredibility important and deserve to be considered treasures.

This is an ongoing project for us, spanning almost three decades now. And it couldn’t have been accomplished without the enormous amount of assistance we’ve received from top players and amp collectors around the world.

What about Axiom transformers? Where do they fit in?

The Axiom transformer line takes over where the limitations of vintage transformer design ended. No bean counters here—simply the sincere pursuit of answering the age-old question: What if there were no constraints on budget, time, or material quality to achieve the best possible performance? That’s our objective with the Axiom line.

Axiom transformer designs represent many new approaches—new tone with the best materials and designs money can buy, so they’re not intended for the timid or the low-budget crowd. Check out our FatStacks and SuperStacks for the Marshall DSL and TSL families for interesting comparisons.

Mercury’s vintage transformer restoration service has been gaining a reputation for quality work. Why would someone want to restore a transformer instead of replacing it? And vise-versa?

Some vintage amp owners prefer to pay the extra cost of our restoration services, because it’s very important to them that their amps retain authenticity. Collectables or rarities are valuable. They’re of the “why take chances” mind. The high road. But on the flip side, we have pro musicians who insist on touring with their vintage gear. To play it safe, and not sacrifice the tone of their original transformers, they have their techs replace the stock transformers with Mercurys. By doing this, they preserve the original transformers from road abuse while taking advantage of our reputation for tone, durability, and warranty. Restoration of vintage transformers is a tricky and highly specialized art. Sadly, too many of the great originals have been lost forever due to technically inept and musically disinterested people. We see attempts at “rewinds” here all the time.

Occasionally, it appears some people confuse “demolition” with “restoration,” and the preservation of the original tone is lost forever. There’s no shortcut to doing a proper restoration.

I understand you’re doing all of your labor and get all of your materials in the USA. How does that impact your business aside from just the straight costs?

Well, we figured that someone has to do it—and we really do make everything here with 100 percent American materials. There are plenty of products out there stamped with “Made in the USA,” but are actually assembled with non-USA, low-price materials. But yeah, we’re the real deal and proud of it.

Building transformers that make an amp sound good requires highly specialized technologies, highly skilled labor, and the right kind of materials. We love music and owe it to the players out there to do all the work “in-house,” so we can keep tight control over every aspect of our transformer designs. It’s really old-school military spec style, so our transformers don’t vary at all from batch to batch. If you need a replacement transformer 10 years from now, it’ll sound exactly the same as the one it’s replacing.

We’re hard-liners when it comes to not playing shell games with a musician’s hard earned dough and quest for better tone. Perhaps I’m a fool for doing it this way, but I was brought up in a musically minded family. From a very early age, I was taught that music is as important and necessary as food. If there is a day our services are no longer needed or appreciated, I’ll pursue my dream of owning a car wash in the valley, and get into the business of making money.

Any new or exciting projects in the works at Mercury?

Yes, but we’re planning on releasing the news sometime around summer. For quite some time, we’ve been fielding requests for accessories to accompany our transformer line. We’re being asked to apply our know-how to other aspects of guitar amps.

Do you have any advice for guitar players and techs in their quest for tone?

Don’t let anybody fool you—every player has the ability to discern the difference between good or bad tone. Unfortunately, there are a few too many self-styled “experts” who irresponsibly dispense advice without having a clue. As a result, we’ve all seen amps completely lose their tone by being modded to death.

There’s no excuse for the old “damn, I’ve done it this way for many years so it must be right” mentality. More than ever, it’s so easy to seek opinion, advice, and help online and elsewhere. I highly recommend the old textbooks from the 1950s and 1960s as a good place to start on vacuum tube audio circuits.

Do your homework and follow what the smart players are doing—improving your tone isn’t that elusive. If what you have sounds good to you, leave it alone. But if you know your amp’s tone could use some improvement, then start where it begins … the transformers.

Source: https://www.premierguitar.com/articles/Builder_Profile_Mercury_Magnetics

It doesn’t take too much digging to find a laundry list of boutique amp builders using Mercury Magnetics transformers in their products. From Mojave Ampworks to Joe Morgan Amps to kits from MetroAmp, builders have found that Mercury knows their iron. While transformers rarely receive the same level of attention of NOS tubes, speakers, or even guitar cables, they are a major contributor to tone. Think about it—the power and output transformers are the start and end of the line with any amp.

Based in Chatsworth, California, Mercury Magnetics has been building transformers for close to 60 years. I recently had a chance to talk with Mercury’s Sergio Hamernik to dig deeper into their roots, find out what one can expect from upgrading their iron, and what sets Mercury apart. Prior to our conversation, I had the opportunity to witness the remarkable transformation of an Epiphone Valve Junior modified from stock to hot-rodded, using one of their transformer upgrade kits. Not only was it a noticeable upgrade, it was a revelation in just how important the role of quality iron in an amp is. But because it is the single most expensive part of any amp, it’s no wonder we see so many modern amp manufacturers skimp on the iron to keep costs down. Let’s see what the passionate, and often hilarious, Sergio has to say about his part of the business.

PG: I’ve been seeing Mercury transformers in amps for at least a decade. When did you get into the amp scene?

SH: This happens to be one of our most often asked questions. Even though Mercury Magnetics’ roots go all the way back to the early 1950s, there are guitar players who are only now discovering us. But if an industry insider like you has been aware of us for at least a decade, then I suppose it means I don’t need to lay off any of our sales and marketing staff.

I would attribute most of our lingering anonymity to the old days. Back then, most of our clients from the audio community preferred to keep us as a trade secret from their competitors and the press. The typical transformer-savvy amp builder also didn’t usually want to share the credit with us, or reveal what their “unique” technical advantage was regarding audio and tone. Consequently, we were asked to maintain a low profile and generic look for our transformers for quite some time. On occasion, a customer in the know will spot a small “MM” mark on a transformer from an older piece of gear, and ask if it’s a Mercury. Odds are that it is.

It was the guitar amp crowd that pushed us to go above ground. Now Mercury gives any electric guitar player or amp restorer a taste of what the pros were using, talking about in their studios, and among themselves. Many players have told us their amps increased in value when upgraded with Mercury transformers, and this became evident when insurance appraisers began to contact us for verification. However, it wasn’t until the mid-1980s when we began to market our services and various brands to guitar players.

For me personally, I got into the amp scene around the mid- to late 1970s. I just found it to be a nice way to relax from the strain of oversleeping.

PG: Your website shows a large number of amp manufacturers you have replacement/upgraded transformers for. What are your best sellers and why?

SH: There are so many different camps loyal to their particular amp brand, so it would be difficult to single out the best sellers. The best sellers are transitory and change from week to week because guitar amp players are a fickle bunch. That’s why we’ve built the world’s largest catalog of guitar amp transformers where nobody is left out.

But trends tend to follow their own dynamics. And the current worldwide trend seems toward smaller wattage amps—regardless of brand. Conversely, the 100-watt heads are not selling like they used to. Players are gigging with no more than 15 watts and a few pedals. Regardless of playing style, they’re doing just fine abiding by sound level restrictions and kicking ass with the tone we feel Mercury upgraded amps deliver.

These players really get the fact that an amp lacking in tone can’t be fixed with higher power or covered up with a gain mod. An amp that coughs out an asthmatic tone at 50 or 100 watts easily fatigues both music listeners and guitarists. But the audience will stay until the bar closes if the band plays well and sounds great—even with as little as a few watts going through the available PA system.

PG: What can a guitarist expect to hear when upgrading their transformers in a newer amp?

SH: An amp’s transformers are the most important component in determining the quality of amplified guitar tone. And it’s no coincidence that they’re the most expensive parts in an amplifier. Many of the newer amps just don’t have the same “overkill” factor with their transformers as the amps in the ’50s and ’60s. Why? Ignorance and a bean-counter mentality. What’s good for accounting isn’t necessarily good for tone from an amp. Sadly, the people making these decisions are probably not players themselves and don’t seem to realize the damage they’re doing to the industry.

It’s not unusual to find a current production amp with a power transformer running hotter than hell, even without cranking the amp all the way. Or having an undersized, cheaply built output transformer whose sphincter begins to tighten the moment the guitarist reaches for the amp’s volume knob. An amp built around anemic transformers yields only to dull, thin, noisy, fuzzy mids and mushy bass. That’s what makes your notes sound more like farts through a pillow. This overkill factor is probably the only edge that some of the vintage amps have over the newer amps.

We have made it our mission to duplicate the performance of the best original transformer designs of all time. In terms of amplified guitar tone history, these transformers represent the best ever produced.—Sergio Hamernik

Have you ever noticed how most newer amps often weigh less, sometimes a lot less, than the older ones? That’s usually the weight difference between the old and new transformer designs. There is a direct relationship between weight and having transformers that seem to stay cooler and “loaf around” with power to spare, until a player demands more from their amp. It’s like they are waiting around having a card game, waiting for the player to do something. The best vintage tone was born that way. Newer amp tone can be easily improved—if the builder follows some of the same ideas.

Upgrading with quality transformers gives a second chance to a new amp owner to make things right with their tone, by reclaiming that overkill factor. Assuming there are no issues with the amp’s circuitry like bad parts or worn out tubes, a guitarist should hear and feel improvements with the very first pluck of the guitar. They should expect to hear the notes more detailed with overtones, and a quicker and more immediate response to their playing. Clean notes will have less sonic collisions with noise and reveal more bell tones, chimes, etc.

When more distortion is required, the player will sense better control of crunch and when break-up begins to happen. The coughing and hacking that happens when a stock amp is pushed, will vanish with a transformer upgrade. It will be replaced with longer sustains and notes that reach farther. The amp will also sound closer and bigger than the power it puts out—and the bass notes will have a tighter, rounder bottom end. And when pushed, she will still be able to hold that quarter from dropping—no matter how tall her high heels—something most musicians are looking for.

It’s not uncommon for guitarists to report that it took a few weeks of playing to fully realize what they’ve gained in terms of harmonic richness. These players have typically played longer and felt more inspirational emotions sucking them in, as they have invested more time into relearning and becoming reacquainted with their amps.

PG: Many players become very attached to the transformers in their vintage amps. When you create ToneClones or Radiospares and Partridge versions of these classic transformers, how close are they get to the originals?

SH: Radiospares and Partridge are our brand specific clones, whereas ToneClones are “best-of-breed” duplicates culled from the hundreds of other brands that have made transformers over the years.

We have made it our mission to duplicate the performance of the best original transformer designs of all time. In terms of amplified guitar tone history, these transformers represent the best ever produced. In the grand scheme of tone pursuit, these designs are incredibility important and deserve to be considered treasures.

This is an ongoing project for us, spanning almost three decades now. And it couldn’t have been accomplished without the enormous amount of assistance we’ve received from top players and amp collectors around the world.

What about Axiom transformers? Where do they fit in?

The Axiom transformer line takes over where the limitations of vintage transformer design ended. No bean counters here—simply the sincere pursuit of answering the age-old question: What if there were no constraints on budget, time, or material quality to achieve the best possible performance? That’s our objective with the Axiom line.

Axiom transformer designs represent many new approaches—new tone with the best materials and designs money can buy, so they’re not intended for the timid or the low-budget crowd. Check out our FatStacks and SuperStacks for the Marshall DSL and TSL families for interesting comparisons.

PG: Mercury’s vintage transformer restoration service has been gaining a reputation for quality work. Why would someone want to restore a transformer instead of replacing it? And vise-versa?

SH: Some vintage amp owners prefer to pay the extra cost of our restoration services, because it’s very important to them that their amps retain authenticity. Collectables or rarities are valuable. They’re of the “why take chances” mind. The high road. But on the flip side, we have pro musicians who insist on touring with their vintage gear. To play it safe, and not sacrifice the tone of their original transformers, they have their techs replace the stock transformers with Mercury’s. By doing this, they preserve the original transformers from road abuse while taking advantage of our reputation for tone, durability, and warranty. Restoration of vintage transformers is a tricky and highly specialized art. Sadly, too many of the great originals have been lost forever due to technically inept and musically disinterested people. We see attempts at “rewinds” here all the time.

Occasionally, it appears some people confuse “demolition” with “restoration,” and the preservation of the original tone is lost forever. There’s no shortcut to doing a proper restoration.

PG: I understand you’re doing all of your labor and get all of your materials in the USA. How does that impact your business aside from just the straight costs?

SH: Well, we figured that someone has to do it—and we really do make everything here with 100 percent American materials. There are plenty of products out there stamped with “Made in the USA,” but are actually assembled with non-USA, low-price materials. But yeah, we’re the real deal and proud of it.

Building transformers that make an amp sound good requires highly specialized technologies, highly skilled labor, and the right kind of materials. We love music and owe it to the players out there to do all the work “in-house,” so we can keep tight control over every aspect of our transformer designs. It’s really old-school military spec style, so our transformers don’t vary at all from batch to batch. If you need a replacement transformer 10 years from now, it’ll sound exactly the same as the one it’s replacing.

We’re hard-liners when it comes to not playing shell games with a musician’s hard earned dough and quest for better tone. Perhaps I’m a fool for doing it this way, but I was brought up in a musically minded family. From a very early age, I was taught that music is as important and necessary as food. If there is a day our services are no longer needed or appreciated, I’ll pursue my dream of owning a car wash in the valley, and get into the business of making money.

PG: Any new or exciting projects in the works at Mercury?

SH: Yes, but we’re planning on releasing the news sometime around summer. For quite some time, we’ve been fielding requests for accessories to accompany our transformer line. We’re being asked to apply our know-how to other aspects of guitar amps.

PG: Do you have any advice for guitar players and techs in their quest for tone?

SH: Don’t let anybody fool you—every player has the ability to discern the difference between good or bad tone. Unfortunately, there are a few too many self-styled “experts” who irresponsibly dispense advice without having a clue. As a result, we’ve all seen amps completely lose their tone by being modded to death.

There’s no excuse for the old “damn, I’ve done it this way for many years so it must be right” mentality. More than ever, it’s so easy to seek opinion, advice, and help online and elsewhere. I highly recommend the old textbooks from the 1950s and 1960s as a good place to start on vacuum tube audio circuits.

Do your homework and follow what the smart players are doing—improving your tone isn’t that elusive. If what you have sounds good to you, leave it alone. But if you know your amp’s tone could use some improvement, then start where it begins… the transformers. PG

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New Amps on the Block: The Sound of History and Innovation

Byers Amplifiers is a new company with the unique outlook and values of its founder. Trevor Byers worked at the Fender Custom Shop and has seen it all, from carefully reproducing old vintage gear to building new guitars to exacting specification. Trevor founded Byers Amplifiers because he saw a need for amps that no one else is building. One of his amps is an original product, the Byers Model 10, while the other is a faithful re-creation of one of Leo’s earliest K&F amps — an amp so old and rare that the only way to see one is to make a pilgrimage to the Fullerton Museum in California. Byers has unique values regarding the way things should sound, feel and look. We interviewed Trevor at his shop in Corona, California to talk about Leo, the history of these old amps, and the new amps that bear his name.

Where did you get the idea to start an amp company?

It was the K&F that got me started. Working at Fender and knowing the entire lineage, including the K&F era, which is kind of separate, it was really intriguing to see what kind of things he came up with. Because it was so rare, the K&F was really appealing to me.

How did you discover this cool original gear while at Fender?

People would come in with things that were not in regular production and would want to have things done and have items reproduced, and people would come in for repairs too. It was a nice influx of cool equipment coming in, and we would turn around and reproduce it to the best of our ability. One of the first pieces we did while I was there was the “snake-head” Tele set, the first regular Fender-style guitar that Leo built.

Doesn’t that predate the Nocaster?

Yes, in fact I think that guitar was a ’47 or ’48. It had a four-piece pine Telecaster-style body, two inches thick with a small, black Bakelite pickguard, volume and tone control, and one bridge pickup. The snake-head headstock was the style he was using on his K&F lap steels, so it had three-on-aside tuners, with a solid, fat, maple neck with no truss rod — he hadn’t thought about a truss rod yet! They only made a few of them, and they were made as a set with the woody Pro amp.

So, did you put truss rods in the reproductions?

No, but they are big, round, C-shaped necks, and they’re quarter sawn, so they don’t move around too much.

There are actually guys who believe that necks without truss rods sound better.

This guitar is really neat-sounding because we used antique pine. One of my first jobs there was to rough-cut these old pine boards, glue them up, and plug and fill nail holes. Looking at these old-style guitars and amplifiers in comparison to what was being manufactured at the time, I saw a night and day difference. These have a style to them that nobody does any more.

This got me started thinking about K&F. If the circuit for the woody Pro was primitive, then the K&F amp circuit was even more so. The Pro had 6L6s and a push-pull output, and a 15″ speaker — a field coil speaker, which we had a lot of problems with. The K&F amps didn’t use field-coils and were permanent-magnet.

Give us a little background on K&F.

It was Doc Kauffman and Leo Fender. The information on K&F varies, so I can’t give a perfect history. They started around late 1944, and ran probably to the end of ’45 or early ’46, then they stopped making these in mid-1946. Leo had done some really interesting things — he had designed an automatic jukebox and little P.A. systems, and he was working with his radio company. Then, he had an idea for these guitars. He started making them and it became popular enough that he needed a larger investment; Doc didn’t think he could invest in something that looked like a hillbilly guitar, and at that time, that was the type of music played on them.

I remember even up until the 1960s, many jazz guitarists looked down their noses at these and told us, “When you grow up, you’ll get a real guitar,” meaning something more traditional, like a Gibson archtop.

Yeah, so Doc left and the K&F company was dissolved. Finding pieces from that time period is hard because there’s no record of how many were made and there were no advertisements for them. I do have some pictures from George Fullerton that Doc’s son gave him of the first piece that they put together, which is nothing like the ones that went into production. It’s very beautiful.

Did you get to play that original Tele that was copied for this run of instruments?

Oh, no. The story behind that guitar was that Leo was a huge stickler for not keeping prototypes around. There were two of those — the first one was cut up and the second was thrown in the trash. George pulled it out of the trash. He was young and had just started working with the company; he was a guitar player and this was his creation too! He and Leo went to little bars and shows and listened to players. Without telling them what they were up to, they asked the players what they would want in a guitar, which became the basis for their business and designs: being able to change small parts out easily and being able to easily change the neck on a guitar. There was a bit of a stigma attached to their early instruments because they weren’t craftsman pieces — they were functional instruments.

Yes, they were outside the instrument crafting tradition. This was a modernist piece of design, rather than following classical instrument-building traditions.

Exactly. So when I started researching all the K&Fs, I talked to George who was there just after Doc left, and I got as much information as I could from the closest source. Strangely, though they made guitars and amps in sets, many of the guitars still exist while most of the amps do not. I figure that the guitar is a functional piece and all you have to do is change the strings, but if you have an amp go out, it might have been easier to just go buy another amp.

Was it through the process of reproducing old gear, and speaking with George Fullerton, that you became interested in the 1940s K&F amp?

Yes, that amplifier in particular because it was so simple and because the circuit was kind of the predecessor to the Princeton, but instead of having an 8″ speaker like a Princeton, it had a big, large-magnet, alnico 20-30 watt 10″ speaker. This was late ’44 or early ’45, and these amplifiers were made from military surplus parts, so they were all different and had this unique industrial look about them. Design-wise, it wasn’t made to be the prettiest thing out there — it was made to be functional.

So it was just “The K&F Amplifier” and they only made the one model?

No, see that’s the thing, they made one, and we know the record shows from Doc’s writing on the pictures I have, that the first one they made was beautiful! It had wooden sides, a grille cloth that was embroidered with K&F on the front, and a 15″ speaker. The photo says, This is the first K&F [lap] steel, and this is the first amplifier in the U.S. with a hanging chassis and hanging tubes.” Before that, everything was put on the bottom of the amplifier and the tubes all sat up.

And that amp is gone now?

Yeah, in John Sprung’s book, Fender Amps: The First Fifty Years, he wrote that this amp was made as a custom, one-off piece, and it is likely gone now, since the only pictures we have ever seen of it were the from the 1940s.

That would be a fun one to reproduce, wouldn’t it?

Oh, it would be amazing. There was an article in the October 1998 issue of Guitar Player with a 15″ K&F — the style of the K&F that I am reproducing. It was the same cabinet shape, just larger, and it is the only time I have seen a 15 other than that one custom one-off piece.

So what you had was three or four amps, all without names or model numbers which were essentially prototypes

Yes, they were “if this works we will make another just like it” sort of deals. There were two basic models that you see in published pictures. One is the 8″model that looked like a little lunch box. It had one volume knob and one or two inputs, no pilot light, no fuse, and the cord coming straight out — that was it.

The other is the 10″ model, which is the one I’m reproducing. It had two inputs, no fuse, no pilot light, one tone control, and either one or two volume controls, and two channels — which was something completely new. Each channel ran on one half of the input tube, which is what Fender did until the Blackface era in the ’60s.

It’s not a large amp at only 5-6 watts. The speaker was an unknown Jensen model that had a large, plug-style alnico magnet instead of the horseshoe magnet. I am sure every example varied because the parts all varied — the knobs, transformers, everything. The transformer on the one I am reproducing was a replacement transformer right out of an Allied catalogue made by some unknown manufacturer.

How did you originally come in contact with the amp you decided to reproduce?

I worked with Geoff Fullerton at Fender, who became a good friend of mine. Geoff is George’s son, and was Leo’s personal assistant at G&L for several years. He was a builder and engineer there as well. George’s father used to work at Fender in the wood mill where he ran this huge ripsaw, which George, Geoff and I also ran, so I had become good friends with the family.

George is a wealth of information and a really interesting man to talk to. He has great ideas about how things were done, the reason things were done, and craftsmanship. Even though his guitars were not traditional, the craftsmanship that went into them was impressive. They case-hardened every single one of the screws that went into a guitar, so if you had to repair it, you wouldn’t strip out the threads. Nobody does that kind of thing anymore because it is not cost-effective.

When I talked to George about the amp, he told me about one at the Fullerton Museum owned by Phyllis Fender, Leo’s widow. As he described the amp to me, I decided I wanted to take a look at it. Phyllis said sure, so they pulled it out of the museum for a day. I looked at it, taking every picture and measurement I possibly could. I worked with what I had, but it wasn’t enough to do a reproduction. Later on I was able to go back, and they let me take the chassis down and measure every single component. One thing I couldn’t do was turn it on.

You were able to disassemble this old amp down to the component level?

I was. I took my meters down there and measured everything. Not only did I measure it, but I cross-referenced it to the color code because those resistors and capacitors are 63 years old now and have drifted a lot. One of the things I noticed is that he used many of the components because they were the only things he could get. They weren’t exactly the right value for the position they were in, but he put them in there because they were close enough and that’s what he had.

So, I’m looking at it, and George leans over and says, “You know, you’re the first person who touched the inside of that amp since Leo; you’d better be careful!” Because no one had touched it in all those years, the chassis, being made of steel and zinc plated, was pretty much pure white and powdery — I wasn’t about to leave my fingerprints in it!

Are you going to reproduce the zinc plating and everything?

Oh yeah, but I’m not going to relic it or try to make it look old.

Are there any ground issues getting through the zinc?

Yes, you have to grind away the zinc to get to the steel. And that was one of the things; there’s no circuit board, it’s all point to point, and whatever had to be grounded was run straight to the chassis right there. It was function over form.

What year was the original produced?

I don’t really know if it is one of the earlier or later ones, although I think it is earlier. There is a kind of complex cutaway on the top of the amplifier and a relief on the cord panel that is pretty much decorative. Those two things are also on the 15″ amps that we know were the first ones made. Later examples don’t have either of those features on them, so it is likely an early piece.

Did your experiences at Fender and taking apart the old K&F amp lead to your decision to start an amplifier company?

The K&F thing led directly to my own amplifiers. That amp was amazing and cool, but it was so rudimentary. Boutique amplifiers are becoming a bigger business now and I though it would be interesting to see if I could do my own interpretation of the design.

I was looking at all these beautiful Fender guitars that we were making, the amazing Custom Shop guitars with custom finishes that people wait years for. There are some really nice-looking amplifiers out there, but most of them look like big Tolex suitcases.

It all started me thinking about something that was small enough that you wouldn’t worry about it getting banged around, with the form plus the function, and replicating some of the beauty of the guitar finishes. That really appealed to me – no one was doing that. Finishing it like a guitar, the correct way, is such an art. I wanted to make them so they would match people’s prized instruments.

Over the years, guitars and their finishes have gotten more elaborate, but you aren’t doing that with the new Model 10; it is using simple shape, texture and color for the amplifier, rather than the busy style of many expensive guitars.

I started out spending hours designing cabinets, and the right one just hits you. This one was simple; it effectively gave room for my logo, but with some different elements. I have 1″ radiuses on the corners instead of ¾”, which makes the amp look more spherical, instead of looking like a big square

It gives it a softer, more attractive appearance.

I started the design of the amp with the cabinet, and I got that nice angled swoop to the front, which was simple, not complex — you see some of the amps from the 1940s that had great grilles on them, and some were so complex. Once I got the design for the cabinet down, and I knew that I could physically produce it from a woodworking standpoint, I knew how much space I had, so I could work on the chassis and circuit layout.

Tell me about the Model 10’s circuit and electronic design, and the sounds you were going for.

Well, George introduced me to Bill Sterle who started working at Fender around 1960. Bill is an audio engineer who designed a lot of the original Blackface amps.

Having someone who was there and who designed amps telling me why they made certain decisions is so much different than starting with copies of what Fender, Gibson, or Marshall did. I learned distinction between the amps Bill made and the Fender amps of the 1950s, which were the easiest and simplest designs. The Blackface-era amps were much more complex designs and they were really trying to do different things with the preamps to keep them cleaner.

When Bill was designing things, he stressed that distortion is your enemy — that’s the school of amp design he came from. You have to have the cleanest representation possible. I went to Bill’s house for hours and he would describe everything from tube heater circuit design to what you want to get accomplished in the preamp section, the phase inverter section, and the power section. He told me once you get going on the tone controls, you can go crazy because there are so many variations in tone circuits — not only what you use, but where they are placed.

I wanted to have a 10″ speaker in there. A 10 just has a clarity that you cannot get from an 8″ speaker, and I didn’t want to go as big as a 12. 10s have a really neat sound to them if you find the right one. I knew it was going to be either a small, single-ended design or a cramped, push-pull design. I ended up starting off with a small single-ended design.

So, design wise, you met some of the original guys who developed modern guitar amps, and took it from there, as if you were in that era.

Oh yeah, and every single element that was put in the amp was based on what I was trying to accomplish in the circuit, not based on something I was trying to copy. My initial intention was to make it really straight and clean, without a ton of bells and whistles. It is a single-ended design with a 6V6 power section and a 12AX7 preamp tube.

I looked at a lot of Internet message boards for guys who are building amps, and for players in general, to find out what kind of modifications they were making and what they wanted out of an amp. I tried to keep it really simple and clean, but I did put in a few things that I thought would expand the tone a little more.

Is there a tube rectifier?

No tube rectifier in this. In such a small, single-ended amp that putting one in would be more of a novelty than anything functional. Not putting one in allowed me to use a smaller power transformer and to clean up the power and make it more stable, along with giving me more space to do other things in the chassis. Also, when I went back and talked to Bill Sterle, he threw his hands up and said, “Tube rectifiers are absolutely worthless!” [Laughs]

My impression is that stout, well-built power supplies produce robust tones, especially at high levels. When you are pushing the amp, and you’re not clobbering the power supply, the amp doesn’t freak out as much. If I want a little sag and compression, I use a compressor!

Well, yeah. It’s all relative though, because there is a ratio between the voltage and the current that the plates see. You push harder, sand the plates, and try to draw more current. If the current isn’t there, then there is going to be a difference in the tone.

I started with a solid-state rectifier and that is the only solid-state piece in the amp. In the preamp, I used more of a Blackface preamp design, where I split the 12AX7 in the middle because the amp only has one channel. I do have two inputs on the amp, but one is just hotter than the other.

So there are only two tubes in the amp?

Only two! It’s simple — there is just a treble and a bass control. With all passive tone controls, if you use the control, there is a certain amount of insertion loss, so on bass control I put a switch so you could remove the tone controls from the circuit completely.

The Model 10 has the standard volume, bass and treble controls; then there is the switch. What does it do?

It takes out the negative feedback loop. You turn that off and bypass the tone controls and it will crunch just like an early tweed Champ. Even with only two tubes and three knobs I wanted to be able to have a range so it isn’t just for one style of play; it is an amp that you can play around with and get a cool tone out of.

It has an amazing array of tones for having so few controls.

I have designs of every shape and size, but this is where I wanted to start. In the larger models, I am going to do a 15-20 watt amp, and I may do as much as a 30-35 watt one as well, though I don’t want to come out with a 100 watt monster.

I think people are starting to re-evaluate how much wattage is really needed.

You know, one of the many helpful things I learned from Bill Sterle was how to test everything correctly. Lots of amp makers out there will say, “This is a 5-watt amp,” and that’s what they assume because a similar one was made by Fender, but Fender tested where the wattage comes up just before distortion, on every one, and that’s how we test as well.

The Model 10 puts out almost exactly 5 watts. It has a cathode bias power section and I go through and measure every single one of those tubes and every single output section of each amp to make sure it is right for this design. I don’t want to run these as hot as I possibly can to get every last watt out of them, because it is hard on tubes. I offer NOS tubes as an upgrade, and they are not making any more of them! I run them right in the middle where you get great tone and good longevity.

What tubes have you been using?

Right now I am using Electro-Harmonix preamp tubes and JJ power tubes. I think the JJ 6V6 is a really neat tube. They can handle a lot of plate current, and they sound good.

If somebody wants a Model 10, how long would it take?

I have all of the parts ready to go, but I have a six to eight week lead time on the custom-colored cabinets, including shipping. It takes about four weeks for the paint to be completely finished, because it has to be perfect. It is a guitar finish on the Model 10 and it’s done just like any expensive guitar finish. The amps are built to order, though I may stock certain colors here and there.

It’s exciting to see the founding of a company with such an amazing product. Do you have a price set for the Model 10?

It looks like the Model 10 will be $1050, at least as an initial release price.

You spoke earlier of having several color choices and perhaps some clear finishes on nice wood available.

The cabinets right now are poplar for the solid colors, and ash or alder depending on whether the finish is a blonde or sunburst one, just like a guitar.

If someone asked you what your amp sounds like, what would you say?

Well, what I was trying to achieve was a combination of the tweed Champ and Princeton, combined with a Blackface Champ and Princeton. I wanted to be able to combine all four of those amps together so you could get a really grungy, overdriven, tweed tone or a really clean, clear tone with or without tone controls.

Tell me about the K&F reproduction amp, is that currently in the pipeline?

That amp is 99% done. Because this amp has never been done before, and because the parts are not off-the-shelf parts, everything is different from what is currently available. Everything had to be done from scratch; transformers had to be custom wound, and chassis had to be custom made — and the chassis are not normal dimensions by any means. The tubes are all NOS tubes, because there is no current equivalent to them.

It’s an octal socket preamp tube isn’t it — a large base and pins like a power tube? What tube is that?

It’s a 6SC7 medium mu triode and a 6J5 triode in the preamp section. Each channel gets half of that triode. It’s a pretty low-gain tube actually; it’s not overdriving the preamp circuit a lot like the later 12AX7s often do. There is also a 5Y3 rectifier and a 6V6 output tube. Both input signals merge into a 6J5. Instead of putting one channel with one preamp tube, he made two channels that merged into one preamp tube. There’s one volume control for both channels. The circuit is a lot different than a modern amplifier. Leo was doing it to see if it would be functional, and it was very rudimentary and basic.

The octal preamp tubes give a really unique sound to the amp. They don’t drive it very hard, but it does put out a pretty thunderous crunch when you want. I am keeping it as historically correct as I can, with carbon comp resistors, Mallory 150s as the tone caps, and all cloth-covered wiring, which I don’t do in the Model 10. I am not trying to reproduce a look in the Model 10, but am going for the best possible sound, so I’m using all the best components and wiring by today’s standards.

You selected the components for the Model 10 by listening to them, didn’t you?

Yes, but the K&F is a little different. It’s not wired like you would wire something today; it has series heaters, so you get that hum in there that makes for a unique sound. The only changes I made were necessary for safety. Of course, there is a fuse in this one, along with a 3-prong AC plug. Other than that, it is rudimentary in every way. The tube sockets are spot-welded to the chassis.

Did you actually replicate the spot welds?

Oh yeah! Lots of guys would have riveted the sockets in place, but that was an extra expense, so they spot welded them.

It probably had a terrific ground connection.

It does. I found an original output transformer and power transformer and had Mercury Magnetics reproduce them for me. The speaker was a 10″ Alnico plug-style speaker rated at 40 watts for a 5-watt amp, so it was way over-engineered for the circuit. Most Alnico speakers have a horseshoe shaped magnet, but this one has 2½” donut-shaped magnet. It was also used for higher-end audio and larger-wattage amps. It makes for a really heavy speaker, but it’s really neat. This Weber is the closest to the original speaker that is available.

How much is the K&F reproduction amp going to cost, and when will it be available?

I’m trying so hard to get it finished! I am talking to a paint manufacturer about the wrinkle paint we need, and if that works out we’re in business with getting the K&F out. We should be ready in October at the latest, and the cost will be about $1000.

Playing the Amps

I brought my 1987 hardtail Tom Anderson to Byers‘ shop where I got to play through the first Model 10 off the line and a K&F reproduction prototype. Here is a sample of what I heard:

Model 10

The Model 10 is a beautiful amplifier. If your favorite custom guitar builder built an amp, it would look just like this.

The Model 10 is clear and detailed in the way that only minimal circuit paths can be. Set clean, with the tone controls engaged and the feedback loop in, the highs and lows are well-balanced, the tone circuits do what you wish they would, and the result is a sound that makes you want to play more. Turn off the feedback loop and things get woollier and more tweed-like. Switch off the tone controls and the amp gets a more aggressive, throaty attitude going.

K&F Reproduction

The K&F reproduction amp is totally different from the Model 10 and totally different from almost anything I have ever heard. I can almost hear Charlie Christian playing one and I suspect that today’s players will find musical uses for this tone. The K&F reproduction is very big and a bit wooly-sounding, yet not muffled or dull at all. It gets pretty powerful sounding when you push it hard.

Source: https://mercurymagnetics.com/pages/news/PremierGuitar/PremierG-10.htm

If you want to nail Clapton’s tone, a crucial part of the equation is the amplifier. With a little ingenuity, John Wiley shows you how to turn your reissue Bluesbreaker combo into the real deal.

A unique distinction of early Marshall amplifiers is that none of them within the same model line sound exactly alike. Partly attributable to founder Jim Marshall’s penchant for working with budding British musicians and working many of their suggestions into his designs, and partly due to the difficulties of locating reliable parts suppliers, Marshall’s early designs each had their own personality. For instance, Marshall’s Model 1962 combo was, itself, an ordinary amplifier; however, one particular Model 1962 used by Eric Clapton with John Mayall and the Bluesbreakers had such a revolutionary tone that it created a new sound in the still-young world of rock n’ roll.

In 1965, Clapton found himself the featured guitarist in John Mayall and the Bluesbreakers. Armed with a 1960 Gibson Les Paul and the Marshall Model 1962 combo amplifier, he single-handedly discovered a combination of guitar and amp that produced an extraordinary howl — Clapton achieved his trademark sound by playing the amplifier at full volume. The sound was full-bodied, authoritative, but not overly distorted; it easily cut through the other band instruments. The sustain was pure, the treble notes sang and the bass registers exhibited a “throaty” bottom. At such high volumes, the amp was prone to feeding back, and this provided an awesome effect to the overall sound.

This image, from the Beano LP, shows Clapton tuning up, with his Model 1962 in the background.

The blistering tone was captured on vinyl and released to an unwitting public as John Mayall and the Bluesbreakers with Eric Clapton; also known as the “Beano” album, it quickly shot to number six on the British charts, even amongst the din of other popular British and American pop groups such as the Beatles, the Animals, the Rolling Stones and the Beach Boys. That LP’s impact soon spread to America and abroad, inspiring legions of new guitarists around the world — especially influencing musical rebels in the United States. Clapton’s playing style, combined with a ferocious amplified tone, seemed to inject a new and exciting dimension into the young blues-rock genre. But none of this could have happened without the small British amp company, Vox. Models like the AC30 would provide the “British Invasion” with its unique sound, and convinced Marshall to build a compact amplifier for his new company; the initial development of Marshall’s first combo took place in early 1964. In a 2003 interview with Musician’s Hotline magazine, he claimed the Model 1962 was built at the request of Eric Clapton. “Eric used to practice in my shop and he was one of the first guitarists to ask me to build a combo,” Marshall recalled. “He wanted one so it would be easy for him to put the whole thing in the boot [trunk] of his car.”

Unfortunately, that Model 1962 disappeared, with Clapton himself unsure of what became of it; years later, it would become known as the holy grail of combos. Although those early combos had great tone, no two sound exactly the same. Two decades later, the Marshall reissue would sound nothing like it at all.

The Reissue

For many of us, the year 1990 brought an answer to one of our greatest wishes: the Marshall Model 1962 2×12 combo was finally reissued. The idea had apparently been in the works for quite some time, as evidenced by this author’s correspondence to a Marshall factory director, Keith Carnall in the late months of 1984. Carnall’s reply stated, “We have thought many times about running a ‘vintage special,’ with valve rectification and all the other old goodies… let us just say for now that it is an idea that we will continue to work around and perhaps you will get your wish granted.” Although Clapton was not aware of the amp being reissued, Marshall christened it the “Bluesbreaker,” in his honor. When asked in a 1989 Guitar World interview he replied, “Did they really? How sweet. I didn’t even know that. How does it sound?” Marshall simultaneously introduced the Bluesbreaker and the JTM45 in 1990, along with the new JCM900 series.

At a cursory first glance, Marshall did an outstanding job recreating the Bluesbreaker, as it externally resembled the original with the distinctive and elegant Marshall styling. Just like the original, it was rated at 45 watts and came with two Celestion speakers. The cabinet dimensions measured 29.13″ wide by 23.62″ high by 9.25″ deep, and black vintage Tolex coupled with a vintage-style Bluesbreaker grill cloth completed the package. Electronically, the 1989 reissue used two 6L6 vacuum tubes for power, three ECC83 (12AX7) preamp tubes and one GZ34 rectifier tube. In 1993, Marshall replaced the 6L6s with 5881 vacuum tubes. Tonally, the Bluesbreaker reissue had a unique and fine sound of its own. It produced varying degrees of that buttery smooth sustain, while retaining that traditional Marshall crunch.

But just how close was this new variant to the original Model 1962? To the true Marshall collector, and to the rare few who actually owned the genuine article, the differences were immediately apparent. In Michael Doyle’s book, The History of Marshall, he pointed out that the cabinet was too small and the grill cloth was not right. But the major disappointment was not in the appearance, but the sound the amplifier produced. While the sound was good and had plenty of Marshall crunch, it was definitely not the sound of the original. And for that reason, I began a quest to change the sound of my reissue into something more closely resembling the original.

Hitting the streets in 1990, the Model 1962 “Bluesbreaker” reissue was plagued with discrepancies out of the box. The cabinet was undersized by some 30 percent, with a depth barely over 9″, while the original measured in at 10.5″. The reissue’s overall width was almost 30″, while the original was 32″. The most reasonable explanation for these differences would come from the use of output tubes originally selected for the Model 1962. Although the very first combos incorporated the smaller 5881 vacuum tube, Marshall designed the Model 1962 for the more prevalent but enormous Coke bottle-shaped KT66 vacuum tube. The usage of this particular tube necessitated the deeper 10.5″ cabinet.

Likewise, the cabinet’s construction differed significantly from original specs. The Model 1962 Series I was built using pine planks for the cabinet with multi-ply birch baffles; the Model 1962 Series II was completely constructed with multi-ply birch plywood (more about these series differences in a moment). The reissue used particle board for the cabinet and plywood baffles.

Finally, the speakers supplied in the original combo were G12M “Greenbacks,” rated at 20 watts each. This speaker utilized an Alnico magnet, providing sweet, warm tones and a smooth midrange — an essential ingredient for that “British chime.” At 20 watts, the speaker could barely keep up with the tremendous overdrive of the amplifier when it was at full volume. Marshall, however, equipped the Bluesbreaker reissue with 25-watt Greenbacks, featuring ceramic magnets. While they lacked the chime of an Alnico magnet, they could withstand twice the wattage and had a fine sound of their own.

The Model 1962 Back Story

However, before we dig in and modify our reissue Bluesbreaker, it would behoove us to understand where it all started. In 1964, while the Beatles made their first appearance on the Ed Sullivan Show, and the Civil Rights Act of 1964 was enacted, Marshall was busy introducing its very first combo. Because it was the very first series, it is historically referred to as the Model 1962 Series I. Interestingly, the 1962’s model number did not refer to a particular year or significant event in time. Until the 1980s, Marshall’s distributor and financial backer Rose-Morris used these numbers arbitrarily, using the prefix “19” for all of Marshall’s product line.

Jim Marshall wanted his new range of combos to be versatile; as a result, he designed the Model 1962 with two 12″ loudspeakers and used the JTM45 bass chassis (Model 1986) electronics. The Model 1962 was described in the Marshall catalogue as a “Bass/Lead” unit, making it an extremely versatile amplifier that could be used by guitarists and bass players alike.

But just how close was this new variant to the original Model 1962? To the true Marshall collector, and to the rare few who actually owned the genuine article, the differences were immediately apparent.

In addition, a second combo with four 10″ speakers — the same configuration used in the Fender Bassman — was offered to players. Marshall’s 4×10 version was referred to as the “Lead” and utilized the JTM45 treble chassis (Model 1987) electronics. This 4×10 configuration, designated the Model 1961, was designed for guitar use only. Both Model 1962 and 1961 were purposely marketed as the British equivalent to the vastly popular Fender Bassman, and they offered quite a bargain for British and European musicians. The Model 1961 retailed for a scant $165 American dollars and the Model 1962 retailed for $170, while the Fender Bassman was nearly double at $300. Both models went into production in late 1964.

Cabinet and Construction

The cabinet dimensions for the Model 1962 (2×12 configuration) were 30″ wide by 24″ high by 12″ deep. The 1961, incorporating four 10″ speakers, maintained square proportions, measuring 28″ wide by 28″ tall and 11″ deep. The Model 1962’s width is 2″ wider and 1″ deeper than the 1961’s to accommodate the dual 12″ speakers.

Marshall amplifiers would also gain a reputation for their ruggedness. Marine ply birch was used for cabinet construction, as the laminated layers of glued veneer plywood provided greater overall strength than a singular plank of yellow pine, which was the wood of choice for Fender amplifiers. These early Marshalls did not use the “finger-lock” joints that would become standard on all Marshall cabinets a few years later.

The Marshall ads above suggested the reissues matched the originals; in reality, there were significant differences.

Marshall cabinets were also visually appealing and had the look of richly appointed furniture. Black PVC (polyvinyl chloride) material, similar to the General Tire invention known as “Tolex,” was used for the entire exterior of the cabinet. This smooth, black fabric was different from the black “Levant” Tolex Marshall would use later.

Accenting the cabinets was Marshall’s elegant grill cloth. The company’s catalogue referred to this early cloth only as, “contrasting speaker grills,” not actually describing the color or pattern of the cloth material. However, it was known as the “white” grill cloth and had thin, horizontal gray lines running through it. Also included on the earliest models were three leather straps, attached to the top of the cabinet and similar to the Vox AC30. These amplifiers weighed in at a very heavy 70 pounds, and the sheer weight meant that it wasn’t long before the leather straps would stretch and break. In early 1965, an improved, single plastic strap which was stronger and larger in size replaced the leather ones.

The very first Marshall combos produced in late 1964 used what was known as “Vox-style” cooling vents, which allowed the heat produced by the transformers and vacuum tubes to escape efficiently. Two vents were installed into the top of the cabinet, similar to the Vox AC30. The vents were rectangular in shape and had a metal screen riveted inside.

Chassis Electronics and Components

The internal chassis that included all the electrical components was made of 6061 aluminum sheet metal. Aluminum has excellent non-sparking and non-magnetic characteristics, making it ideal for electrical shielding purposes and chassis use. It is, however, not as strong as steel and would fatigue and sag under the weight of the heavy power and output transformers. To remedy this, cast aluminum end blocks were riveted inside each end of the chassis to add strength and rigidity. The chassis were 2.5″ deep and purchased from a sub-contractor named Smiths.

The JTM45 used one circuit board screwed inside the aluminum chassis, providing a central platform for the various electrical components. Prior to 1965, Marshall used Tufnell perforated circuit boards; from 1965 to 1967 a subcontractor called Heathfield manufactured the circuit boards, which can be recognized by the drilled holes on the solid sheets.

The output transformer was officially known by Marshall as the “RS De Luxe.” It was light gray in color, with horseshoe end bells. The maximum output rating was only 30 watts, and all three transformers used on the JTM45 — the output, power and choke — were purchased from Radiospares, an electrical component clearing house.

The first combos produced in late 1964 were equipped with two GEC (General Electric Co.) KT66 vacuum tubes. The original design of the JTM45 called for the Tung-Sol 5881 tube; because this tube was used in the Fender Bassman, it was the tube of choice. However, supplies for the 5881 were scarce and the KT66 was used as a replacement. The KT66 provided more bite and distortion, suiting the JTM45 perfectly, and unlike the EL34, it was not overly saturated and did not sound mushy. The KT66’s bottom end was solid and exhibited clarity, while the trebles were almost “violinlike” in nature and very smooth. Much like the Fender Bassman, the JTM45 became known for its unique sound, primarily because of this tube.

Four 12AX7 (designated the ECC83 in Europe) preamp tubes were supplied in the 1961 and 1962, and both featured a tremolo circuit as a standard appointment. These amps also included tube rectification, which added to the sound’s overall smoothness. The 5AR4 rectifier tube (designated the GZ34 in Europe) was used on all JTM45 configurations, including models 1961 and 1962, and was the same rectifier used in the Fender Bassman and many other classic American amplifiers.

The JTM45 also incorporated two “can” style filter capacitors; the number of capacitors used, and their respective value, was a significant factor in the overall sound of the amplifier. One LCR Co. 32ìf x 32ìf at 450 volts was mounted on top of chassis near the power transformer, and one LCR Co. 16ìf x 16ìf at 450 volts was mounted inside the chassis just beneath the power transformer — the standard arrangement for the JTM45.

KT66 tubes as were used in Clapton’s Model 1962.

Speakers & Logo

The Model 1961 would utilize four 10″ Celestion Alnico speakers, while the Model 1962 would use two 12″ Celestion G12 speakers, handling 15 watts and featuring an Alnico magnet. The Alnico magnet contributed to the amp’s unique and sparkling sound, referred to as the “British chime.” A basic style of logo badge was used on these very first combos, and is commonly referred to as the “gold block logo.” The badge was rectangular in shape and was very simple, having only the Marshall name in bold block letters. The letters were black in color on a background of gold, although silver was sometimes used.

The Clapton-Spec Combo — One of a Kind?

The particular Model 1962 amplifier that Eric Clapton used with John Mayall and the Bluesbreakers was unfortunately lost, without knowing its exact pedigree. It was definitely an early edition of the Series II combo and was built during a continuous procession of production changes and revisions. The typical production run of any of the Marshall line could have differing components from amp to amp — it is not an exaggeration to say no two amps were exactly alike. This was primarily due to the inconsistent component suppliers Marshall used at the time, and partly because booming business made record keeping (serial numbers, production quantities, etc.) a low priority — existing serial numbers are not reliable or even logical, and production numbers are at best derived from employee recollections. Therefore, determining just how many amps were built exactly like Clapton’s is extremely difficult. The following list of features, derived from exhaustive research, best represents the Clapton’s combo specs. This particular amp is pictured on the reverse side of the “Beano” LP. The Series II cabinet was designed by Marshall’s chief designer Ken Bran, and incorporated a more modernistic styling. Its dimensions were 32″ wide by 23″ high by 10.5″ deep. The cabinet was sturdy and constructed of 3/4″ marine ply, incorporating one slot-style cooling vent and covered with black Lavent vinyl. The grill cloth was the classic gray and white striped variety later known as “Bluesbreaker” grill cloth. The cabinet was smartly accented with gold hardware attachments for the cabinet handle.

Chassis Electronics and Components

Clapton’s amplifier utilized the JTM45 bass guitar amplifier electronics known as the Model 1986 and the same chassis used in the Series I, made of 6061 aluminum sheet. One circuit board screwed inside the aluminum chassis was used and it was manufactured by the Heathfield Company.

Mounted on top of the chassis was the heart of the amplifier — the transformer. The defacto JTM45 output transformer was the “RS De Luxe;” however, since it was rated at only 30 watts, it was not ideal. Clapton’s amp may have utilized the newly acquired Drake Companytransformers. The output transformer would have been Model #784-103, with an 8K primary Z, and the power transformer would have been Model #1202-55. Utilizing the Drake transformers would explain why Clapton’s combo did not sound like a “typical” JTM45amplifier.

Clapton’s amplifier utilized two GEC KT66 output vacuum tubes. The preamp circuit included four Mullard ECC83 tubes, with one dedicated to the tremolo circuit. The Mullard GZ34 rectifier tube was again used. Two can-type filter capacitors were used: one LCR 32ìf x 32ìf at 600 volts mounted on top of the chassis near the output transformer, and a second LCR 16ìf x 16ìf at 450 volts mounted inside the chassis.

Speakers

The amp’s speakers consisted of two 12″ Celestion G12s, rated at 20 watts, 15 ohms, and with an Alnico magnet. These speakers were essentially the same as those used in Vox AC30s, and are extremely fragile when pushed beyond their limit. Because Clapton ran the amplifier at full volume, the Alnicos may have been damaged. He may have replaced them with the higher wattage, ceramic magnet Celestion Greenbacks.

The Model 1962 reissue schematic.

The Objective: Convert a Reissue to Clapton-Spec

I started my investigation into obtaining this sound over 20 years ago. In addition to the “Beano” studio CD, there were other John Mayall albums that included “live” cuts from Eric Clapton’s time with the Bluesbreakers. Although these recordings were done with crude equipment, they captured the raw and unrestrained sound of Clapton’s guitar and amplifier. To my ears, these recordings were most realistic, as they lacked any studio treatment. I quickly knew what sound I was after.

In 1994, Mike Doyle’s book, The History of Marshall, was released and included an eye-opening chapter on the Bluesbreaker. That chapter confirmed the reissue’s lack of authentic sound, and it became obvious that in the amp’s conversion to Clapton specs the only salvageable pieces would be the electrical chassis, the control panel and some of the cabinet hardware — the cabinet and speakers would have to be replaced.

With that, I decided to do the conversion in a logical progression and planned to document the progress. I preferred a progressive approach, as it would give me a chance to analyze each change made separately. In addition, since this conversion would be fairly expensive, it would be easier on the budget to purchase items over a period of time. The changes required could be grouped into three categories:

1. Cabinet: Since the reissue cabinet was too small, it could not be used. I’d have to find a new cabinet that is the correct size. The reissue’s casters, amplifier strap handle and the plastic Marshall logo badge could still be used.
2. Electronics: Swap out the reissue output transformer for a vintage correct one, re-tube with KT66 vacuum tubes and change out the filter capacitors.
3. Speakers: Change to an Alnico magnet type.

I should note that it is possible to make deeper changes, such as replacement of the circuit board, resistors, potentiometers and components, plastic tube sockets, and rewiring of the chassis to original specifications. These additions will make the electronics of the amplifier more authentic, but will not noticeably improve the sound. These additions also significantly increase the cost and add more time to the project.

The steps I have outlined above will reproduce the amplifier tone as heard on the live cuts of Clapton with the Bluesbreakers, as well as the “Beano” record. In fact, after making these changes, your Bluesbreaker will no longer be a mere reissue — it will sound like the real thing!

The new cabinet is over 2″ bigger than the reissue cabinet, resulting in a fuller sound.

Step 1: A Bigger Cabinet

There are now several competent amplifier cabinet makers building exact replicas of the Model 1962 Series I and II cabinets. Be sure these makers use the required multi-ply Baltic birch plywood, correct black Tolex covering, vintage gold veining and the surrounding white piping. It is also wise to have them confirm the correct cabinet dimensions, as the Series I and II are two completely different cabinets. To save some money, you could use the Marshall logo, casters and other hardware from your existing reissue. Two excellent cabinet makers available on the internet are Vibroworld.com and Swansoncabinets.com.

For the first phase, I ordered a new cabinet from a cabinet maker on the internet — to ensure accuracy, I supplied them with a CAD drawing of the Series II dimensions and features. I was very pleased with the results I received a few weeks later. I removed the chassis and speakers from my Marshall reissue and reinstalled them in the new cabinet. Even though the new cabinet included pre-drilled holes and Tnuts for the speakers, it still took some time to make this switch. While switching cabinets, be careful to ensure the speaker and amplifier connections are right.

For testing, I used a Gibson Les Paul Heritage 80 model. After re-checking the chassis and cabinet connections, I turned on the amplifier, and let it warm up. I started at low volumes and progressively turned up the volume to 10, all while keeping the other settings such as presence, bass, middle and treble at 10. Upon hearing the first chords, I was immediately struck by a new “openness.” The amplifier seemed to breathe and had a new, airy sound to it — it did not sound as tight as the smaller reissue cabinet. With 30 percent more space in the cabinet than the reissue, the trebles seemed revived and the amp now had an “airy” bottom-end. Comparative testing with another stock Bluesbreaker reissue verified the tonal improvements.

An interesting side note; in 1997, Marshall produced a limited edition white Bluesbreaker called the “Limited Edition 1997.” It was basically was the same amplifier as the 1989 reissue, with one important difference: the limited edition’s cabinet incorporated the deeper 10.5″ thickness, as can be found in the original Model 1962 Series II.

Step 2: The Electronics

Before digging into the guts of the Bluesbreaker, a word of caution: this phase deals with potentially dangerous electrical voltages and it is highly recommended that only a trained and competent amplifier repair person or skilled electrician perform these tasks.

This phase involves swapping out the reissue transformer, changing the 6L6 vacuum tubes to KT66s, and replacing the filter capacitors.

The Transformers and Tubes

There are now some good vintage transformer manufacturers around, so one has a choice in the matter. Since the original Model 1962 used a Radiospares (RS Deluxe) transformer, the objective here is to get one like it. When I did my conversion, I purchased a Mercury Magnetics Model O45RSL-8-M(MercuryMagnetics.com).

When it comes to power tubes, the only one to use here is the revered KT66. There are however, a few brand options available. One could either purchase a matched set (two are needed) of original GECs, or purchase a pair from companies offering reissue KT66s. The European and American tubes manufactured in the 1950s and 60s (new old stock) are superior in tone, quality and reliability. Tubes now manufactured in Russia and China such as Groove Tubes, the new Tung-Sol, and JJ/Tesla offer comparable tone and are reasonably priced. Since these tubes are made overseas, it is difficult to isolate a superior brand, and although tonal quality is improving with better consistency, tone remains an individual choice. For my conversion I used a matched set of Chinese Valve Art tubes, and was not disappointed.

Since we are changing out the power tubes, it is highly recommended to replace the 12AX7 (ECC83) preamp tubes as well. Again, there are several good options here which include SED Winged “C,” Electro-Harmonix and Ei/Ei-Elites. Replacing the GZ34 (5AR4) rectifier tube is also a must for optimum performance. The same tube suppliers listed above carry the GZ34, in varieties like Sino, Sovtek, or the very expensive Phillips metal base.

Filter Capacitors

Replacing the big can-style filter capacitors will definitely give your reissue more clarity. Filter capacitors are rated in the ZZxZZ format. The reissue Bluesbreaker has two 50×50ìF capacitors which must be replaced. The blue 50×50ìF filter capacitor, located closest to the GZ34 rectifier tube should be replaced with a 32×32ìF/600V capacitor. The other 50×50ìF gets replaced with a 16×16ìF/450V capacitor. JJ and F&T are two good options for filter capacitors.

Caution: These changes should only be done by a good amplifier repairperson. Also remember to have your KT66 vacuum tubes rebiased. I had renowned Bluesbreaker guru Ted Breaux finalize and tune my Bluesbreaker electronics.

Before using the amp at full volume, a suitable warm-up for the newly installed electronics should be done by simply powering up the amp and leaving it on Standby for a good hour or so. While it’s warming up, pay close attention to any unusual odors or burning, as a bad solder joint or incorrect wiring could cause a short circuit.

Once the amp has warmed up, with no guitar plugged in set the Presence, Bass, Middle and Treble controls to 10. Then start increasing the volume of Input 1 slowly, listening for any peculiar pops or sizzling noises in the process. If you don’t hear or notice anything unusual, you should be set to go.

For the “sound” test I used the same Gibson Les Paul Heritage 80; for the tonal comparison, I used the Primal Solos CD, starting with the solo in “It Hurts to Be In Love.” Before cranking the amp to 10, I employed the same gradual progression of low volume checks, listening for any unusual noises and so on. When I got to 10, I was astounded!

I was able to produce the same overtones and harmonics as the recording.

Likewise, the treble response was spectacular. I had read that Clapton used a Rangemaster treble booster with his amp, but I was getting the “sound” without one. The F9 chord in “Have You Ever Loved a Woman” shimmered and went into harmonic overload, exactly like the recording. The only notable difference was in the bass registers, as it seemed harsh at times and slightly lacking in tightness — additionally, some of the treble response seemed a little harsh. But I was definitely hearing 95 percent of that Clapton-spec sound, as no EL34 or 6L6 had ever sounded like this. It was now time for a speaker change.

The cabinet after installing the Weber Blue Dogs.

Step 3: The Speakers

I narrowed my choice of Alnico speakers down to the Celestion G12 Alnico Blues and the Weber P12B Blue Dogs. The Celestions were rated at 15 watts while the Webers were rated at 30 watts — I decided to try the higher-wattage Weber P12B. After swapping out the reissue Greenbacks for the new Blue Dogs, I played the amp at lower volumes for several hours. At these levels (5-6), I was pleasantly introduced to the British chime of the 1960s. Early Beatles rhythm and lead guitar sounds were easily obtainable, particularly within the mid and bass ranges.

I then tried the full throttle test. At full volume, I was in for quite a shock — the mid and bass ranges nearly cut me off at the knees. The treble side was knife-edge harsh and the amp was monstrously louder. I was obviously disappointed, as none of this remotely sounded like a Bluesbreaker. I had read that Alnico speakers may require an extended “break-in” period, and I hoped that was the case here.

I removed the Blue Dogs from the Bluesbreaker cabinet and reinstalled them into a 2×12 cabinet I was using for weekend gigs. After a few weekends of extended playing, I noticed the sound changing, as I was having to re-adjust my amp head settings. After a few more weekends, I definitely noticed something happening. It was now time to re-install the Blue Dogs back into the Bluesbreaker cabinet.

Upon trying it again, something magical happened to the overall sound of the amplifier. Right there in my basement, and out of my rebuilt Bluesbreaker, came the sound. I was flabbergasted, as it sounded incredible. I must have played the amp all night. I was nailing all of Clapton’s Bluesbreaker riffs, and they sounded identical to recordings. The A minor solo break in “All Your Love” sounded amazing, and like the recording, it was drenched in sustain and overtones. “Stormy Monday” from Looking Back was spot on.

Finally, my Bluesbreaker renovation was complete. The amp sounded just like it should, some 40 years ago. Doing this yourself makes all the difference, as you become a part of the equation — with a little work and dedication, you can experience Marshall just as Clapton discovered it.

Source: https://mercurymagnetics.com/pages/news/PremierGuitar/PremierG-08.htm

Amp Transformers

Guitar amp articles

Amp Transformers, Output Transformers & Chokes

I am often asked how upgrading an amplifier’s transformers will improve tone. It’s a simple enough question, but the answer is a little complex. First off, let’s examine what an output transformer is and why someone would inquire about replacing it. Then we’ll get to some things to consider when replacing your amp’s transformer.

The output transformer in a push-pull guitar amplifier is the last stage of the audio path before getting to a speaker—it’s one of the large blocks of metal mounted to the amp chassis (or speaker, as is sometimes seen in older amps). The transformer’s function is to convert the high-voltage/low-current signal from the amplifier’s power tubes into a low-voltage/high-current signal to power the speakers at a low impedance. It is responsible for how efficiently the audio power of an amp will transfer to the load of the speakers, and it prevents hundreds of volts (DC) from passing to the speakers.

There are different reasons why a person would want to change their output transformer—the most obvious being a blown or damaged unit. This can happen when an amp is operated without a proper load, such as not having a speaker plugged into the amp or driving a different speaker impedance than the one the output transformer is looking for. Another reason to replace a transformer is to upgrade quality and tone. Because transformers are the most expensive component of an amplifier, it is common for amp manufacturers to cut costs on the size and quality of them. A large transformer simply has more iron, so not only are the material costs higher, the weight of heavier transformer will affect a manufacturer’s shipping costs.

In regards to tone and how an output transformer affects it, it’s my opinion that an output transformer does not change an amp’s character. A new transformer will not change an amp’s DNA or make a Marshall sound like a Vox. After all, an amplifier’s tone is the sum of all of its parts—tubes, capacitors, wiring, speakers, etc. If you were to run clean water through an old, dirty water filter, you would ruin what the water had to offer before being filtered. It would still be water, but changed in a way that detracted from what it could have been. The output transformer plays a very large role, but is not everything in shaping an amp’s tone. Upgrading it takes what the amp already is, and then enhances it. Physically larger output transformers generally sound larger, since they have a larger window for tone to flow through. Tone is usually clearer, fuller and truer.

If upgrading or replacing your amp’s output transformer is in your plans, there are a few things to consider. First, and most importantly, the amp should be unplugged, all tubes should be removed, and all voltages in the amp should be fully discharged. There are lethal voltages inside an amplifier, so do not service your amp if you don’t know how to properly discharge all voltage.

Secondly, be aware of the different mounting styles of transformers. There are three basic mounting styles: vertical, horizontal, and flat. Vertically mounted transformers sit taller than they are wide, with the laminates in a vertical position and the end bells positioned perpendicular to the chassis. Horizontally-mounted transformers are still a vertical mount, but are tipped on their sides and are wider than they are tall. Transformers that are mounted flat have the laminates facing horizontal, and the bell ends are stacked vertically. One should also note if the transformer is a two-hole or four-hole mount, and that the mounting holes will not line up exactly if the transformer you are replacing is not an exact replica. In such cases, it will be necessary to carefully mark and drill new mounting holes into the amp’s chassis.

Finally, make sure the replacement transformer will physically fit on the chassis and in the cabinet it’s going into. It is easy to forget the size of the speaker and its affect on the space left in the cabinet. Measure twice to avoid disappointment!

It is very important to note the wiring of the old output transformer. I often clip the old transformer leads and leave a little bit of the old wire so I can see the color and location of the original. Keep in mind that green or black is not always ground, and that manufacturers often use different colors for the ground. A new replacement transformer should come with a schematic, so pay careful attention to it and note the proper wiring.

With the new transformer installed and all wiring and solder joints double-checked, it’s time to turn on the amp. Before doing so, be sure to turn all pots all the way down. If the primary leads on the transformer are reversed—a simple mistake to make—the amp will produce a loud squeal. And if the volume were to be up with this squeal, it would scare the life out of anyone. A simple swapping of the leads going to the power tube plates will take care of this issue. It is a good idea to use a variac to ramp the amp’s voltage up gradually, going easy on the new output transformer’s maiden voyage. When the amp is running at full-voltage, you should then turn the amp off, reinstall the tubes, turn it back on, and double-check the power tube bias. The new output transformer will need to break-in over time, but all that’s left now is enjoying your amplifier’s improved tone!

Remember that an amplifier’s tone is the sum of all of its parts. The output transformer is one very important part that easily gets overlooked and often suffers from cost-cutting-minded amp builders. So experiment! After all, your amp is your voice, so why not make it the best voice it can be?

Source: https://www.premierguitar.com/articles/Why_and_How_to_Replace_Your_Amplifiers_Output_Transformer

Amp Transformers, Output Transformers & Chokes

Question: I heard that rust is bad for my transformers. I’m being told that rust causes an increase in eddy current losses which will heat up and further damage my transformer. Rusty transformers will also hurt my tone, so I must remove the rust or replace the transformers to make my amp operate properly and extend its life.

Answer: Nothing could be further from the truth. While iron possesses the necessary magnetic properties, it is also electrically conductive. Eddy currents are circulating currents in the core induced by a magnetic field emitted by the energized primary winding of the transformer. These electric currents are undesirable. The coreis acting much like a shorted secondary winding. They are power-robbing losses that convert your guitar playing (input power) into heat that beats up your transformer. This effect is certainly not helping your tone!

On the other hand, rust (iron oxide) is a nonconductor of electric current. The high resistivity of rust reduces eddy current losses. Since iron is also a conductor of electric current and the goal here is to minimize eddy currents, which is why the construction of the core is made up of a stack of thin plates of iron (laminations) which are insulated from each other by an oxide (rust-like) coating. This confines the eddy currents and prevents them from circulating between the laminations. The higher resistance created results in a reduction of power losses within the core.

What’s this mean in plain English? Back in the early years, manufacturers of laminations intentionally exposed their iron to moist air to encourage rust to naturally form on the surfaces as an insulator! Like a fine patina on an antique bronze the rust on your transformer could be viewed as badge of honor. Assuming that your transformer doesn’t have other problems like coil damage from excessive moisture exposure (common with paper bobbins), you can actually expect some improvements in output transformer tone and lower losses in power transformers as rust develops.

If you are still bothered by the cosmetic aspect of rust, never scrape off the rust to the point of exposing bare metal because you will bring back those nasty eddy currents. Instead, brush off the loose particles and re-paint the area with varnish. If you want to send your transformer to Mercury, we can re-dip it in varnish and bake it for a small fee. Transformer evaluations are always no charge providing you cover the shipping costs to and from Mercury.

Source: https://mercurymagnetics.com/pages/_misc/FAQ.htm#Transformer_Rust

I have a 1987 model 50-watt reissue Plexi head that is completely stock. I don’t care for the sound of an attenuator, and I want this amp to sound as close to an older Plexi as it can get. What do you recommend for the best possible tone?

We get this kind of question nearly every day. I’m sure you’ve heard the phrase, “No two Plexis sound the same,” but there’s a ring of truth to that. One could surmise that if Marshall (as well as other amp manufactures of the time period) ran short of parts it would substitute the next-closest thing to keep the production line moving along, which would logically explain the numerous differences in circuitry that have been documented. Additionally, a lesser known fact is that there were also transformer differences in the early Plexis.

If, for you example, you were to substitute one power transformer for another, the B+ (high voltage) might be higher or lower, which would have a direct impact on the tone, performance and feel of the amp. This helps to explain why some Plexis are harsh, overly bright and don’t break up well, while others break up nicely, have a warmer tone and have a better overall feel.

How can you get your reissue Plexi to sound, feel and perform more like an older Plexi? First, let’s agree that tone is a matter of taste, and in matters of taste there can be no right or wrong. Simply put, it comes down to whatever works best for each individual player based on his or her preferences in regard to tone.

Transformer Upgrades: Simply changing the output transformer is enough to satisfy the needs of some players. For others it also requires upgrading the power transformer as well as the choke. I’m sure there are many of you who may wonder, “Why change the choke?” Rest assured that selecting the right choke can make as much of a difference in tone and feel as changing the output transformer, and the same can be said about upgrading the power transformer. Many companies offer Plexi-spec output transformers as well as a complete Plexi-spec replacement transformer kits. We exclusively use Mercury Magnetics and would encourage you to check them out. Look at the transformers from other companies too. If you aren’t certain what you use, please feel free to call us.

Components: This has been covered at great length on numerous forums and bulletin boards across the Internet. Can upgrading the components on the PCBs (Printed Circuit Boards) make an audible difference? Yes, absolutely. What are the best components to go with? Again, this is a subjective thing. Upgrading the coupling capacitors (caps) from the box style caps to higher-quality caps (e.g. SBE Orange Drops, Mallory, Hovland MusiCap, Solen, Auricaps, etc.) will no doubt provide an overall sonic improvement. For cathode bypass caps (caps in series with the cathode resistors in the preamp section), the majority of players seem to gravitate toward non-polarized cap cathode bypass capacitors versus the polarized bypass caps. For resistors I personally prefer metal film, since they don’t drift off value over time and will produce less noise/hiss over time. Opinions vary from one person to the next, though, so use whatever you’re most comfortable with.

Master Volumes: You can go with a pre- or a post- PI (Phase Inverter) master volume. Both have their advantages, but both have disadvantages as well. The easiest to hookup would be a pre-master volume (see JCM800 2204/2203 schematic), which is beneficial in that the EQ section (Bass, Mid, Treble) is much more active and responsive. There are various kinds of post-PI master volumes. Some are extremely transparent, while others color the tone of the amp in an undesirable way. The advantage to a post-PI master is that you can get the vintage distortion or breakup much like you do when you turn a Plexi to somewhere in the range of 5-7 (on a scale of 1-10). Our V-Plex Series amplifiers employ the post-PI master volume. Some of the Plexi reissues have not come with screen-grid or input-grid resistors. Without these resistors Plexis tend to sound squishy, muddy and smeary. For EL34’s I recommend 5-watt 1K screen-grid resistors, and for the input resistors (pin #5) I recommend .5- watt 1.5K metal film.

Feedback resistors: We have seen many different values in the older ’60s Plexis. We’ve also seen the resistor assigned to the 4-, 8- or 16-ohm tap as well as the positive side of the speaker jack. Do they all sound different? Yes, they do. Remember, there is no substitution for hands-on experience when it comes to determining what sounds and feels the best. I hope this helps you find the tone you want. Have fun tweaking your amp.

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Because there are so many kits and builders in today’s DIY and boutique amp market, you no longer needed to be a super shredder or fretboard wizard to have a “signature” amp. Nope. Today, the only thing between you and the amp of your dreams is a little bit of cash.

For roughly the price of a boutique amp, you can build and customize your own rig – Tolex, grill colors and materials, cabinet plastics and wood types, tube combinations, speaker pairing and sizes, power output – virtually any idea you can think up, and chances are someone can make it a reality. I recently build a 2×12″ 18-watter to my own specifications. Here’s how I did it.

I hemmed and hawed between something more modern-looking and a traditional Tolex-covered cabinet. There are great cab builders who use all kinds of wood. Some variations of the classic tone woods (pine and Baltic birch) are wonderful – walnut, wedge, maple, mahogany, basswood all produce different qualities, and craftsmen are using combinations of them to produce interesting tones. But because I was making my own version of a classic, I decided to go with a traditional cabinet.

The one custom mod I asked Peter to include was to build the cabinet of pine; I’ve always loved the resonance and timbre of pine cabs, and it’s a bit lighter than the birch used in Marshall cabs.

Peter convinced me that while pine would work, I should stay with a birch baffle to retain some of the characteristic bite conveyed by the wood used to build the amp we’re copying.

To further the customization, and give the amp a touch of fun, I decided on white Tolex. Per my request, Peter aged the cab to give it a broken-in appearance.

While I wanted this amp to sound like a Marshall 18-watt, I also wanted more control over its tone. I wasn’t interested in tremolo or reverb as much as saturated overdrive and the ability to obtain overdrive at less than ear-bleed levels. I opted for a Ceriatone DIY kit, which they assembled for a small fee. And since I already had a drawer full of old mustard caps and NOS resistors, I figured I could upgrade some components down the road, if necessary.

Ceriatone had a two-channel Treble/Middle/Bass (T.M.B.) circuit with a Master Volume on the second channel that fit the specifics I was after. I was happy with the quality of workmanship – it had solid solder joints, all around.

I firmly believe transformer iron makes a big difference on an amp’s overall tone and character.

For an 18-watt amp based on a Marshall, you have a power transformer and an output transformer. In the 1940s and ’50s, some power transformers could handle up to eight times the output of an amp! The more muscle, the better the tone.

While an adequate power transformer insures an amp will run at optimum output and efficiency, the output transformer is what really counts when it comes to delivering tight lows and harmonics, and musical sound quality at different volumes.

There are companies making custom transformers and reissuing certain classics, and they all have distinct sounds and characteristics; some are brighter, some more harmonic, some offer crisper note separation, etc. Choosing one is, of course, a matter of taste. Since I was going for that classic dark vintage Marshall sound, I went with Mercury Magnetics, which offers a few choices when it comes to Marshall-style 18-watt output transformers, all based on classic Radiospares transformers from the ’60s and ’70s (which is what Marshall used in the 18-watters). I opted for the handwired ToneClone.

I played with various speakers – Jensen, Celestion Alnicos, old CTS speakers from a Hammond organ, and a few more mismatched combinations. But the thing that really worked was a pair of mid-’60s 20-watt Celestion greenbacks. To my ears, there’s something about an aged magnet in a speaker that makes it less harsh. The 20-watters captured that sweet spot. They’re articulate, punchy, and I really like that they don’t have the boomy low-end of their 25- and 30-watt counterparts. Aside from that, I had an old set that were signed by Alexander Dumble! Not that it makes a difference, tonally, but it’s cool!

Now, some guys wouldn’t pay that much mind to grillecloth, beyond its color. But there are dozens of variations out there… but none of them capture the look – and more importantly, the “feel” – of the vintage “Bluesbreaker” amps.

In the ’60s, Marshall used a rubbery grillecloth material that has never been accurately reproduced. It muffles and colors the amp’s sound in a way that’s unmistakable to old Marshall amps. While I wasn’t opposed to using some funky grillecloth, I really wanted to capture that classic sound. Luckily, I stumbled upon E.C. Collins, who hand-makes a near-duplicate cloth.

While there are plenty of manufacturers making quality tubes these days, I had all the vintage tubes I needed lying around from old projects. The only one I had to source was the rectifier tube, an NOS Mullard EZ81. I had two Valvo EL84s, which I used for the power tubes, and a vintage Mullard, and two vintage Amperex Bugle Boys, which I used for the three ECC83 preamp tubes.

There’s no reason to sacrifice quality to hit a price point. Sure, you might have saved a few bucks if you buy a mass-produced amp, but if you’re after tone and personality, with a little bit of time and planning, you can build the amp of your dreams.

My amp turned out better than I could’ve hoped, and since every component was sourced to my own specs, it truly speaks to me! VG

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Caption: Photo shows measuring the temperature of a transformer’s laminations with a NON-CONTACT thermometer. In this shot the transformer is outside of an amp and hooked up to a Variac. This type of handheld thermometer does not require direct contact with the transformer and can read temperatures from a safe distance.

• Temperatures below 100°F are generally considered “cold” or “cool” in terms of the operating temperature of a transformer.
• Temperatures between 100°F and 110°F are considered “warm.”
• Temperatures between 110°F and 120°F are considered “very warm.”
• Usually temperatures above 120°F are considered “hot.”
• Temperatures above 130°F may cause second or third-degree burns on adult skin.

Transformers designed with high-temperature insulation systems can run safely at temps up to 200°F. But remember, a hot-running transformer is an angry transformer.

Want to know the health of your amp’s transformers? Take their temperatures! A hot-running transformer is an angry transformer and it may very well be telling you its dying. It could be an older vintage unit that is showing signs of aging materials. Or, you may have a newer amp with a far-to-common undersized “runt” transformer. Either way heat means a waste of power and potentially shorter transformer lifespan — not to mention strangulation of your tone. Transformers should normally run between warm to very warm temperatures. Hot is a bad sign — especially in the case of output transformers (OTs). Make sure that other components are not the cause of excessive transformer heat. For example the tubes should be the only hot-running component in your amp. But keep in mind that if they’re too close to a transformer they could artificially heat the unit, also leading to damage over time. Of course there’s more to the story, but if you are in doubt then see your local amp tech or give us call. By the way, Mercury recommends using a non-contact thermometer to take your readings. If you do have a dying transformer it’s time to think about a rebuild, replacement or upgrade. Remember, Mercury offers you not only the best-sounding and most reliable transformers, but more tonal choices than any other company!

Did you know that hot-running transformers not only drain your amp’s reliability but can also cause major tonal issues?

The problem is so common that many players mistakenly assume that transformers should run hot. Not so. In fact, excessive heat is an all-to-common sign of under-powered “runt” transformers that are potential tone-killing accidents waiting to happen.

Heat is nothing more than a symptom of energy loss. And hot-running transformers certainly do nothing to contribute to your tonal quality. Energy loss means one thing—inefficiency. It’s like driving a hot rod around with the parking brake on. Think of “runt” transformers like brakes on your amp, making your tone dark and muddy.

Here’s why: Insulation aging is accelerated by higher temperatures. As insulation temperature approaches redline, resistance begins to decrease. A breakdown occurs when insulation becomes damaged by the unchecked rising heat. Transformers wear-out from the effects of usage, time and high temperatures.

Exposure to electrical spikes can also contribute to stress on the transformer’s insulation system. If that wasn’t enough, the coils of wire inside your transformer are often beaten up by vibration! These internal vibrations sometimes cause the magnet wires to rub against each other, wearing off the insulation and causing short circuits.

The life expectancy, and resulting tone, of a transformer is completely dependent upon its insulation system. The build-quality and consistency of the transformer design must be greater than the working conditions and stresses you subject it to (i.e. how hard and often you play). This explains yet another reason why transformers wound with paper tube bobbins are the most susceptible to thermal- and aging-related breakdowns.

Remember, a hot-running transformer is an angry transformer. It is angry because it is overstressed. This may not cause your amp to immediately fail, but eventually it will. The ideal transformer should run between cool to very warm. Excessive heat is nothing more than the amp’s circuit demanding more power than it’s transformer can give. The proof is when you correct the problem. Swapping the “runts” with higher-efficiency upgrade trannys gives you enhanced tone by way of increased headroom, higher loaded voltages, better response and often a very perceivable tonal depth improvement.

Getting you both superior transformer tone and reliability isn’t easy. At Mercury we tackle the problem by making uniquely musical transformers for specific guitar amp designs. Each transformer is made by hand, one-at-a-time, then individually hand-tuned for maximum tonal performance — and coolest running temperatures. No other approach comes even close.

With Mercury transformers you’ll have one less thing to worry about in your quest for great and consistent guitar amp tone.

Source: https://mercurymagnetics.com/pages/_misc/FAQ.htm#Take_Your_Transformers_Temperature,%20Part%20I

Like the pedal business, the number of amplifiers being built by smaller builders has mushroomed into a garage and basement Skunkworks industry that is constantly changing. New guys pop to the surface and ride the momentum created by chat rooms and social media, while others quietly slip beneath the surface in an unfortunate imitation of Beach Boys drummer Dennis Wilson, never to be heard from again. The desire amongst certain guitarists and collectors to own the latest, supposedly greatest new amplifier is a power drug, and for some, a hard habit to kick. We enjoy discovering small batch alternatives to familiar archetypes and affordable production amps, too, but since we’re doing so on your behalf, our initial evaluation process lacks the unbridled enthusiasm of a new owner who has already made the plunge financially and emotionally. Still, when a giddy reader calls or writes asking us to review their new killer amp, we routinely hit the builder’s website, send an introductory email and wait for a response. Such was the case with the Tungsten Cremawheat and builder Adam Palow

Ultimately, the Cremawheat turned out to be another exceptional amplifier as our review reflects, but as is so often the case, the story behind the name on the face plate is as interesting as the amp. Listen….

TQR: You mention on your website that you were inspired and intrigued many years ago by your first tube amp. Do you recall what it was?

It was a 1965 Fender Vibro-Champ that was missing the face plate, and the grill cloth had been replaced with a red and black check material that looked like it had been on a sofa. I think I was around 16 when I got it, and no matter what I played through it, the amp sounded very musical compared to the solid state practice amps had used before. It was the beginning of an obsession. I started chasing down vintage Fender amps wherever I could, and I met a guy who showed me how to safely drain the stored voltage in an amp, how to use a soldering iron, and he explained how bigger caps produced more low end. From that point forward I was on my own, and everything I have done since has been the result of trail and error and experimentation. I’m limited in some areas because I don’t necessarily understand all the theory, but in another sense it’s empowering because I am chasing feel and working in an intuitive way rather than strictly by the “book.” My favorite part of the build is constructing the board and wiring the chassis. If there is any artistic expression in building an amplifier it’s in the way the board is constructed. Of course, in the larger picture, it’s completely meaningless.

TQR: What were the most significant things you learned through hands-on experience working with guitar amps, and the five years you spent working on Hammond organs with Bob Schleicher?

The thing that blew my mind the most once I had acquired multiple identical models of the same amplifier like the Fender Blackface Bassman and Bandmaster was how different they could sound from each other even though they were built with the same components. That also carried over into my work with Hammond organs, because every large Hammond console also had its individual voice, and I attribute that to the accepted variance in parts values, and individual and very unpredictable drift in these values over time. You also see random parts stacking where some of the capacitors may have been oriented the correct way and others not. When all the caps are pointing the right way you can have an amp that sounds faster, and when they are oriented the wrong way the amp can sound slower. On the old caps there was usually a band marking the outer foil, and whether or not they were oriented correctly often just seems like chance. Some companies paid strict attention to that and others did not. Even if I am building ten identical amplifiers in my own line, there are going to be variances between them – not only in the tolerance stacking, but in the way the tubes bias to the cathode resistor. I have an absolute minimum standard – it has to inspire me or I’m not going to ship it out, but every once in a while you drop in the right rectifier and the right power tubes and they just match up perfectly with the cathode resistor and it makes your hair stand up on end. Magical. Yet that same amplifier with a different set of tubes may not do the same thing.The Hammond organs are unique because not only do they have an extremely rich and harmonically complex signal, but they have infinite sustain with no transient attack unless you’re using the percussion feature, so when you’re dealing with Leslie power amplifiers you’re not dealing with sag. You’ve got compression going on because you’re driving it with a very wide band signal, but because there is no transient, you’re not experiencing sag, compression and release in that order. I spent a lot of time rebuilding Leslie amplifiers, and there was a very specific type of distortion coming from those 6550 Tung-Sols – a low, grinding, wooly distortion kind of like the Marshall of the organ world in a lot of ways, and I caught that sound in my head. It was very musical, and it had a lot of clean qualities, but also an outrageous amount of overdrive on tap, and even when it was driving hard there was still enough clarity to retain a musical quality in the distortion. You could really hear the notes and the intervals between them, and that’s the complaint I had with a lot of amplifiers outside the vintage world…. They swung so far into breakup and distortion that you lost the clarity of the notes. There was more noise than tone, and the place I’m coming from is a more musical place. The other aspect of my work with Hammonds is that I gained a huge amount of experience with vintage Jensen Alnico speakers.

TQR: We have always wondered if the Jensen speakers used in Hammond cabinets were similar to those made for guitar.

In the Leslie, the Alnico P15LL and later C15NLL bass driver that shoots down into the rotating horn were definitely not guitar speakers by any stretch. The 12 inch Jensens I’ve seen bear all the same markings as standard Jensens for guitar, the differences being that they have black frames with no Jensen sticker, and the Hammond code starting with the letters “AO” have been silk-screened on the frame. I have pulled P12Ns out of old Hammond A100s, as well as P12Qs, and if they were specifically designed for organ, they are also the best sounding guitar speakers I have ever heard, and I have used them to base my own speakers on made by Weber.

TQR: Which prompted the development of your own line of proprietary speakers?

Yes, and I didn’t really have to start from the ground up because they had already come close to the mark, but I wasn’t hearing the same extended frequency response that I was hearing from the vintage speakers, and it was just a matter of developing a different recipe. Fortunately, when Ted was still alive we went through the process of mixing and matching components, just trying to get that sound. I didn’t care if the parts were period-correct – I just wanted them to sound right. I tried to do the same thing with the ceramic line, but we just never nailed it and I never put them into production. Of course, the goal in developing the Alnico speakers was to produce the low-wattage, medium fidelity, $6 replacement speakers that they were originally.

TQR: Looking at the different models you build today, it’s obvious you prefer the sound of tweed-era amplifiers.

Yes, I cut my teeth on blackface amps, but when I built my first tweed Champ I became one of those guys that ditched my pedalboard and plugged straight in. For me it’s all about that very alive midrange, and the dynamic response you get out of the power section. I was instantly hooked. I also have a fondness for the lower power brown amps as well, but when it comes to what I personally want to plug in to and play, I really need to feel the response of a tweed power section.

TQR: What’s your approach to specific types of capacitors used in building your amps?

You have to let your ears be the guide, and everyone hears things differently. Every quality capacitor has its place, but I personally prefer the sound of Mallory 150s in tweed amps. Other people feel that they are too bright in the upper mids until they break in. I tend to break in my amplifiers for 72 hours and when I take breaks from building I’ll plug into every amp that’s burning in. The truth is, everything matters. In the Cremawheat, for example, there different capacitors are used in the tone circuit to color the tone in a certain way. It’s one recipe. I also use custom-wound Mercury Magnetics transformers in everything. Some of them are custom-wound because I wanted a different gauge of wire, and others because I wanted a different secondary voltage. When we’re talking about power transformers, voltage that you’re sending out to the circuit makes much more difference than the brand you’re using. With output transformers it becomes more critical. Some people want to hear a darker transformer, others high-end clarity…. Some people want a smaller core so it saturates sooner, and others want enough iron so that it never saturates. All of those factors play not only into the sound, but they hugely affect feel.

TQR: Can you briefly summarize each model you build?

The 8 inch version of the Mosaic comes with either the stock 5F1 (Champ) output transformer or the oversize version, which nets you perhaps an additional 2 watts. You get more punch rather than volume. I also build a 12 inch Mosaic Mark II with an additional tone knob, which gives you more bass.

The Cortez was intended to be my flagship model until the Cremawheat came out. The name was inspired by Neil Young’s Suma album – you can just hear the tweed all over it. Its 12W-15W with 6V6s and it bumps up to about 18W with 5881s or 6L6s. It’s basically a straight-ahead 5E3 design.

The Cremawheat is my attempt to retain the tone and feel of a great 5E3 Deluxe, while giving you the dynamic range that would otherwise be lost in the output transformer and speaker with that amp. Those were two choke points on the 5E3, and the third being the massive amount of bass that’s being sent through the circuit, which causes it to distort so early. The other significant feature in this amp is the British-voiced Scumback speaker. It adds punch to the dynamic range, and enough bass, but not the ragged and loose 5E3 style low end.

The T35 covers the 5F4, 5E5-A and 5E7 circuits for the Bandmaster, Pro and Super. They were basically the same chassis with a couple of minor resistor changes and three different speaker configurations, and I tend to prefer the 1×15 and 3×10 versions. It’s the only fixed bias amp I offer. I like the T35 series, but I tend to gravitate toward the cathode biased amps and most of my customers seem to as well.

If you took the 2-input ’55 Bassman, which shares a lot with the Super, Bandmaster and Pro amps of that era, and cathode biased it in a 2×12 speaker format, that’s kind of where the Blue Point sits. When you pay it clean, it sounds very American in the style of a mid-’50s Bassman, and as you turn it up, you get more coloration from the British-voiced speakers. It starts to cross the Atlantic into that early JTM-45 Bluesbreaker tone, but stops short of a later Plexi amp.

The Buckwheat is the follow up to the Cremawheat. It’s a 6L6-based, 30 watt with the Scumback H-75, which is their version of the pre-Rola G12H. It has a significant amount of headroom over the Cremawheat, and the speaker produces a glassier, high-headroom tone with a bigger transformer and a larger cabinet that leaves more air around the notes. If you’re a Telecaster player, for example, who wants more headroom with just a little hair, this is that amp.

TQR: Will you build specific amps with different speaker configurations as a head or combo, and what is the current lead time for an amp?

Sure, I’ll absolutely build variations on the stock models – I actually really like the 16 inch Mosaic and I have built several of them. I want to know that I’m building exactly what a customer wants. The lead time right now is eight weeks, and I always try to keep it under three months. I sell direct, and through a small dealer network, but I do enjoy working directly with customers. Depending on what a customer wants, I may suggest a specific change to the stock circuit, and I find that interaction very rewarding Introducing another 15W–20W amp in these pages is nothing new – in the past year we’ve invested a log of ink highlighting amps like Jeff Beck’s choice of a Pro Junior, our vintage ’59 Deluxe and ’76 Princeton Reverb, the Retro-King 18W and the Trace-Elliot Velocette. Why? Because we understand that such friendly decibel levels offer adequate volume for use in small clubs, mic’ed on bigger stages, yet till fill your house, studio or practice room with a mighty roar when needed. Small amps just make more sense today for most players, but like us, you might be wondering just how many ways a smallish guitar amplifier can be designed and built to produce a genuinely unique voice and vibe. You know what you’ve already got, but what might you be missing, and at what point does your quest to discover the ultimate low power amp become redundant, at best? A fair question, and given the nearly infinite variables created by the marriage of different components within different circuit designs, we are happy to report that we haven’t reached the end of the road in the quest for tone quite yet.

Viewed within the board context of the booteek amp landscape, the Tungsten Cremawheat emerges from the box as an uncommonly attractive natural blonde. Offset with gold grill cloth, it scores big in style points without even being lit up. Nor will you find any self-conscious bells and whistles added to an otherwise classic design, as if the builder wanted to get noticed by adding the kind of stuff we seldom really use – like Selmer-style rotary tone switches, pentode/triode modes and toggled boost switches (although Carr has always done those right by bypassing the tone stack). Indeed, this amp is so outwardly attractive, approachable and comely that pulling the back panel off might inspire distant memories of an anticipation experienced in concert with a one-handed thumb and forefinger bra removal technique. (We now pause to allow a moment of fond reflection. Please take your time.) Adam Palow’s skill in assembling and soldering up a circuit board culminates in nothing less than a work of art. Flip the chassis over and the custom-wound Mercury Magnetics trannies provide further evidence of Palow’s commitment to following his muse. In practical terms, you get four inputs into two channels (bright and normal), volume/volume and tone, plus a standby switch and extension speaker jack.

Our first session with the Cremawheat was agreeable enough, but repeat visits left us with a nagging impression that something was either missing, or perhaps technically present, but not being fully reflected in the sound of the amp. Naturally, we used our tweed Tremolux and Deluxe for benchmarks, and the Tungsten sounded subdued and restrained by comparison. We tried different tubes first with no appreciable change, and that’s when we focused our attention on the Scumback speaker. Admittedly, we had suspected it from the beginning, so with the original tubes back in the amp, we connected the Celestion G12H30 70th Anniversary in our ’59 Deluxe cabinet to the Cremawheat, fired it up, hit a big E chord raking a heavy Pyramid pick over the strings slowly, followed by ten minutes of unbridled delirium. Paired with the Celestion, the Tungsten bowed up with increased volume, clarity, dynamic punch, and a gloriously rich tone that easily rivals that of our Deluxe, but with a little more added sparkle. Swapping the stock Electro-Harmonix 6V6s for a pair of RCA 6L6s brought the Cremawheat to climax with an even bigger, more imposing voice, precisely in the style of our ’59. If anything, the Tungsten offered a slightly more defined and chiseled tone as a new amp should when compared to one that has undergone a half century break-in period.

To be fair, we called Adam Palow to inform him that while we absolutely loved the Cremawheat, we were not feeling the Scumback. He agreeably acknowledged that the Scumback was indeed somewhat more subtlety endowed than the Celestion, which is why he offered the G12H as an alternative for players desiring maximum girth, power and growl. Any number of modern speakers would surely sound outstanding in the Cremawheat – but we clearly preferred the more vivid soundstage created by the Celestion when the choice is narrowed to one of the two stock speakers offered. Would we buy and play the Cremawheat? Absolutely. It now reigns among the best on temporary boutique twenty watters, and in four important respects (tone, overall clarity, availability and price), the Tungsten impressed us as an irresistible alternative to a vintage Deluxe and any and all modern replicas

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Something very cool is happening the basement of Mr. Music, Boston’s favorite family-owned music store in Allston, Massachusetts.

After a lifetime of gigging, amp repair, studio building, and tone tweaking for stars like Joe Perry of Aerosmith, master technician Rob Lohr is building some of the finest boutique tone monsters to come along in a while.

I have always been impressed with anything I heard that was built in his shop, located in the basement of Mr. Music. Rob is a person of great detail. A technical question put forward to Rob usually yields a tutorial on the workings of electrons with respect to our favorite instrument, the guitar. Through the years, Rob and I  have had many conversations about what a practical amp should sound and look like. A veteran of the gig scene himself, Rob understands what the working artist needs. In my world, 50 percent of the reason why something sounds good is because it does not need a crew of roadies to transport it, set it up, and break it down. These days, as indie artists, even for high-profile shows in theatres, we usually show up with our own favorite rig. It had better be light and tone-worthy!

When I heard Rob’s Dumbalina, an amp inspired by the legendary Alexander Dumble’s Overdrive Special, I was instantly hooked. Here was an amp the size of a Fender Princeton Reverb that was a very high quality, point to point, hand-made tone machine that had a kick like amps twice its size. Rob Lohr had somehow managed to pack all of the essential features of the best Dumble-inspired amps into a space the size of a Fender Princeton Reverb. He did this with no sacrifice in power (45w) and the highest quality components!

There are many other great D-Style amps whose components are a cut below Dumbalina’s. Yet Rob charges a modest $1800.00 for the basic amp, with additional costs for any custom work. Okay, yes, I did have to pay extra for him to add my name to the front in vinyl lettering with Fender-style script. Don’t be confused though, this is not the “Thaddeus” amp!

With a switchable  4, 8, 16 ohm extension speaker output, the amp offered everything you might need to grow your rig. Small gig: use the onboard 12-inch G12-T75 and walk in with the amp in your right hand and guitar in the left. Large gig: take an extension cab and utilize all of the 45 available watts to rock the stage with two or more 12-inch speakers.

The footswitchable Overdrive channel sounded like the mating of a Dumble Overdrive Special and a Two Rock Custom Reverb Signature. Overdrive that sings without over-saturation and responds to tonal tweaks on your guitar or subtle finger ornaments. The quality of OD of this amp, I will testify, is simply one of the best I have played. The clean channel can be crystal, but if you push it, you can get a singe on the top notes and a roar on the power chords.

The +4 effects loop provides you with the opportunity to use the highest studio grade effects in the loop. Aside from being whisper quiet, plugging in a high-end effect processor seems to lend a three-dimensional quality to the amp that makes it sound much bigger than its physical proportions might suggest. Of course, you can use a dumble-ator or clone thereof to use line level floor pedals, but why not use some of the high-quality studio grade pedals that are coming out these days? TC Electronics makes a couple and so does Eventide. More and more pedal manufacturers are giving you the option of the studio level +4 signal, ready to plug into your D-style effect loop. (See previous post on Effects Loops).

The three switches that you normally find on D-clones for Bright, Mid, and Bass are neatly hidden in Dumbalina: Each  tone knob (Bass, Treble, Mid) has a hidden, whisper quiet, pop-less pull-boost feature which takes the whole thing up to a different kind of 11 heaven. The Volume knob has a presence boost. When the Tone Bypass is engaged (often called Pre-Amp Bypass or PAB in other Dumbl- inspired amps) the treble pull pot doubles as a bass boost. The result is the most useful “PAB” option that I have ever seen with a corresponding increase in low end that makes this feature a very practical and useful option for me. Usually I shy away from PAB because it might sound a little gnarly, or less friendly in lower volume settings, even though it works wonders for cutting through in the heat of the mix at high volumes.

My most recent gig was a power trio gig, a Hendrix tribute concert. I used Dumbalina’s overdrive channel for the solos that were not over-the-top, so to speak. When the band started really bashing, I could get away with using my Tone Bypass to cut through the mix. Really very flexible tones on this puppy! The 45w is just what you need to sing at lower volumes. Push the envelope a bit and you get great power amp overdrive without scaring the non-guitarists out of the room. In addition, there is a master volume/loop send level that allows you to get the tones you are using at lower volumes without changing the character of the settings. A well thought out amp for the working musician. At 34 pounds, the amp is welcome at any gig that I play!

In the studio, Dumbalina reigns supreme. I have just completed tracks for a tribute cd. R&B versions of Jimi Hendrix tunes. I used Dumbalina for many of the guitar solos and rhythm tracks and, well, tune in next year in the Spring to hear what I think are pretty amazing guitar tones.

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Rob builds every aspect of the amp. From the cabinet and grillcloth to the faceplate (painting and vinyl lettering)

the meticulously wired components inside this amazing amp.

Current wait time is only something like three months, since Rob is building each one by himself. I am sure as the word gets out, that list will grow and grow. It will still be worth the wait, I promise!

Here is the icing on the cake: roughly six months or so after you get the amp, after the amp has been broken in. Rob will sit there with you and do the final tweaking of the components WHILE YOU ARE IN THE SHOP! He will look at the levels and settings that you choose and tweak the internal components so that a great amp becomes an even greater amp, tuned to YOUR signature style of playing. This is an amazing benefit and it is the feature that pushes Rob to the front line of amp builders. (Isn’t that why Dumbles became so popular and expensive? Alexander Dumble would tweak them to the playing style of the owners). Rob recently spent 10 hours—yes folks, 10 hours in the basement at Mr. Music—tweaking an amp for client Alex Potts, so he could have it ready for his move to LA. In my Berklee Online course, Funk/Rock and R&B Soloing, I talk about signature tone. Folks like Robben Ford, who within a couple of notes, announce their presence on the recording whether or not you are even close enough to read the album credits. I believe that this amp can open a door to this concept, and with the post-build tweak, you just might be creating some new history.

Here is the latest version of Dumbalina that Rob is completing, with a couple of new tweaks and slightly different cosmetics on the faceplate, which include corresponding faceplate lights for the lighted footswitchable Overdrive and Tone Bypass features: Sweeeeeeet!!

Here is the scoop on Dumbalina, from the hand of the builder himself, Rob Lohr:

CABINET-The cabinet is Grade “A” pine joined with machine cut half blind dovetail joints and internally braced with poplar. I will cover the cabinet with any available tolex and grille cloth, and you have your choice of appropriate loudspeaker*. The standard faceplate is brushed aluminum with black letters, but I can do colors for a small upcharge and you have your choice of knobs**. The handle is a good quality faux leather that comes in brown, black, or blue, and I use 1″x2″  heavy duty rubber feet and stainless steel cabinet corners and hardware.

*speaker must be of appropriate power handling.

**knobs must fit 1/4″ shaft and comply with existing chassis hole spacing.

CHASSIS– The chassis is steel with welded joints and all hardware is stainless steel. The transformers are MERCURY MAGNETICS FBFVL-P 120v power transformer, FC-VIBROL choke and FBFVLR-OS Fatstack output transformer(4,8,16 ohm selectable). I can do selectable AC input for a small upcharge. The tube compliment is: 2x 12ax-7(pre), 1x 6sl7(PI) 2x 6L6GE(output) and a GZ34(rectifier). I use Belton tube sockets and retainers. I use a combination of Alpha, Clarostat, and Bourns potentiometers, Cliff and Switchcraft jacks, plugs and switches. All shielded leads are Mogami console cable. All unshielded signal leads are teflon coated solid copper core silver clad. All power supply wiring is PVC jacketed stranded copper.

ELECTRONICS– 100 percent hand-wired point to point construction. Hand made 1/8-inch fiberglass turret board, a combination of Metal oxide, metal film and carbon composition resistors, Oil and foil signal capacitors, and high quality electrolytics. There are some other solid state components, but they are related to the switching circuits and are not in the audio path.

LIMITED LIFETIME WARRANTY– I don’t warranty speakers, tubes, or output transformers for obvious reasons …but if anything else ever breaks I will fix it for free for ever and ever. Or until I die, which ever comes first.

Here is the bullet list of Dumbalina Specs:

Output power———–45 watts

Tube compliment——–2x 6L6GE, 2x 12AX-7, 1x 6SL7, 1x GZ34

Output Impedance——4,8,16 ohm selectable

Effects loop———— post pre/ pre power half normalled break out with send level.

Foot switches———-Over-drive and tone bypass(PAB). Both can also be controlled by front panel switches and are indicated with both front panel and foot switch mounted LED’s. The footswitch over-rides the front panel switches.

Controls—————-Volume, Treble, Middle, Bass, Overdrive, Level (ratio), send level.

Pull Pots:

Pull Volume————-Bright

Pull Treble————–Hi mid boost

Pull Mid—————–Lo mid boost

Pull Bass—————-Bass boost

Speaker Celestion G12T75, 8 Ohm

Rob Lohr can be reached at Mr Music in Allston Massachusetts at 617-783-1609 or at  robmadoak@hotmail.com

Here are few demo videos that I just did:

OVERVIEW:

Your quest for truly inspirational and superior tone has led you to the final link in the chain – Mercury Magnetics. Premium guitar amplifier power transformers, output transformers and chokes.

Transformer sets are often misunderstood, yet vital musical components. They’re integral to the nuances of your guitar amp’s sound. Far more than tubes, speakers or other amp components, the transformers establish the platform for shaping your amp’s unique sound.

Today’s players are more informed and demanding than ever. They hear the differences and know that both transformer design and build-quality have a dramatic effect on their tone. Indeed, if your tube-based amp is suffering from bland and unexciting tone then it’s probably related to low-end or poorly designed transformers. As amp designers, techs and manufacturers have discovered, the practice of dumping generic, low-bidder transformers into their amps doesn’t cut it any more. And now you know why.

Who uses transformers by Mercury Magnetics?

• The Who’s-Who of top guitar players.
• The majority of top boutique amp makers, world-wide.
• Amp manufacturers who produce high-end and signature gear.
• .. and players like you who are crave the best possible tone from their amps.

Within the player community no other company commands as much respect as Mercury Magnetics. You can depend on our uncompromising, fanatical build quality, consistency and reliability.

All of our transformers are 100% handmade by us here in California, USA. They come with an unheard of 10-Year Workmanship Warranty as well as a money-back Tonal Satisfaction Guarantee.

Who is Mercury Magnetics and why  is our guitar amp project so important to you?

Did you know that tube-based guitar amp transformers are unusual and very different from industrial as well as audio transformers? And did you also know that it is impossible to engineer the “perfect” guitar amplifier transformer from strictly “by the book” specifications? Interestingly, almost all of the great-sounding amp transformers contain either flaws, “happy accidents,” or have other issues in their construction that were not part of their original specifications.

Decades ago, when Mercury’s engineers first discovered these curious phenomena, the music industry was already in the process of losing its references to tone. In the throws of converting to solid state, tube and transformer platforms were mistakenly being relegated to relics of the past. Those who knew the original technology were either retiring, dying off, or jumping ship for the “new improved” way of doing things. By the time we collectively began to realize what was happening to guitar tone, it was almost too late. “Old school” manufacturing had been all but shut down and as quality dwindled N.O.S. (new old stock) components became the last bastion of our tone.

It was during those Dark Ages that the transformer connection to tone was almost lost completely. However, Mercury was there as a hold out — and even when it wasn’t fashionable, never compromised. But as often happens, when an older era fades, the remnants of what made it great were readily available to study. And like archeologists, Mercury’s engineers began sifting through the bones of the most coveted old amps in an attempt to discover what made them better, and often times so different than others.

The resulting products of those studies were the earliest ToneClone and Axiom designs. Mercury quite literally evolved a new science of guitar amp transformer design for tube-based guitar amps from there, and has continued to innovate and revolutionize it since. Perhaps few people realize the significance of these discoveries and the resultant developments. But without Mercury’s catalog of transformer designs, guitar tone as we knew it would have been lost.

We build transformers exclusively for guitar amplifiers. And we’re unique in a number of related ways:

• 100% American made — no hidden imports — we really do make ’em from scratch, right here in California!
• 100% handmade and hand-tuned using only handwound components. We never compromise or play bean-counter games by short-cutting, attrition or using cheaper materials. Each and every transformer is consistent. If you ever need to replace one of our transformers, your amp won’t lose its tone — your replacement will sound exactly the same as the original.
• American-made steel — we’re the only transformer manufacturer who custom orders, from an American steel mill, the unique alloys used in our transformers. These alloys are not only made here in the USA to military specifications, they are not available anywhere else in the world. They’re the same alloys used in the all-time best-sounding transformers during the “sweet spot” era (pre-1965) of guitar amplification history.
• Things are never stagnant around here. Mercury maintains active and ongoing R&D (research & development). All kinds of new and exciting-sounding transformer designs (Axiom series), as well as our ongoing cloning of outstanding transformers mined from the great old amps (ToneClone series). For vintage British amp freaks, check out our Radiospares, Hiwatt and Partridge series. And many modern amps can be upgraded with our APS series — our newest line of guitar amp-specific transformers.
• For any popular amp design we’re likely to have not just one but several transformers for different purposes and different tonal characteristics. It’s always a smart idea to discuss replacement, restoration or upgrading with your Mercury rep. — you’ll find his input invaluable.
• Our transformers are found in the amps of virtually every major player in the world. Many specify Mercury and won’t play an amp without them.
• Mercury transformers are standard components or factory upgrades available in virtually all high-end boutique amps, including Fender’s boutique and custom shop lines.
• Mercury transformers are so highly rated that they typically increase the value of any amplifier they’re installed in.

Protect Your Investment

Mercury’s Amp-Saver™ technology controls the power flowing into your amp – so you can power up confidence every time. The patented microprocessor controlled Amp-Saver automatically works with your amp’s on/off switch – simply plug in, turn on and play.

$169.00Buy Now

Why do I need it?

By controlling the power flow from your outlet, Mercury’s Amp-Saver prevents destructive hard-starting so your amp doesn’t inhale anything harmful. Gentle start-ups are key to prolonging your amp’s life.

How does it work?

The microprocessor controlled Amp-Saver automatically works with your amp’s on/off switch – simply plug in, turn on, and play!  The Amp-Saver and included Copper-Tone Power cord are designed to work seamlessly with your existing setup and You’ll sleep better knowing your transformers, tubes, and especially TONE are being actively protected.

How is it different from other devices?

• Unlike any other product on the market, Mercury’s Amp-Saver incorporates ‘smart’ circuitry to actively monitor the voltage and current at start-up. If something doesn’t look right, the Amp-Saver will go into ‘protect’ mode and save your amp from anything destructive. If no issues are detected, the power to your amp is slowly raised to diminish inrush currents in the mains transformer, filter caps, and tube filaments. The Amp-Saver also offers user-programmable ramp speed (how slow or fast the power is applied), and current sensitivity (offering the ability to fine-tune for your particular amp — more info below).
• Other circuits use passive devices (resistors/thermistors) to blindly slow the inrush current at turn-on. Unfortunately this method adds heat and robs audio amplifiers of the power they need to work their best. Even more sophisticated relay/solid state switchers do not offer active protection if too much current is being pulled.

What is Ramp Time?

This controls how quickly or slowly the Amp-Saver ramps up the voltage and current to your amp. The Amp-Saver is designed to minimize the inrush current at any setting. From the factory, the ‘RAMP ADJ.’ is set to maximum (fully clockwise) which goes from zero to full power in about 5 seconds. This control can be adjusted to your application using a small flathead screwdriver- the minimum setting is 1 second (fully counter-clockwise).

As it ramps, the Amp-Saver status LED will flash a few times and then stay lit green, indicating your amp has been safely started without any detected issues.

What is Current Sense and how do I set it up for my Amp? (Advanced users)

When you switch your tube amp on, the Amp-Saver monitors the power flowing from the outlet into your amp. If the tube amp is in trouble and is drawing more power than it should, Mercury’s Amp-Saver will go into protect mode and shut off the power (indicated by a flashing red status LED).

From the factory, the Amp-Saver ships with ‘SENSE’ set to maximum (fully clockwise). This setting will work for tube amps up to 300 Watts RMS. For advanced users who want to customize the protection for their particular amp, the Amp-Saver Sense control can be adjusted to customize the current protection for your particular amp.  The process outlined below requires you to start with a properly working tube amp – Mercury is happy to recommend an Amp Technician in your area if you require assistance.

As a rough guide, use the table below to match the wattage of your amp to the Amp-Saver ‘SENSE’ setting with a small flathead screwdriver. Using this starting point, switch your amp on and and verify that the Amp-Saver status LED stays lit green after ramping up the power. Some trial and error may be necessary to fine-tune this sensitivity as it needs to be set to a point just above the ‘protect’ mode. If the LED does not settle on green but instead flashes red, the Amp-Saver will need to be reset by unplugging it from your power outlet and the Current Sensitivity control will need to be increased (turned clockwise).

Approximate settings by Amp Wattage:

Next, with your amp turned off, lower the ‘SENSE’ control slightly (counter clockwise), switch your amp on, and watch for the solid green Amp-Saver status LED. Repeat this process until the Amp-Saver LED flashes red – at this point, with your amp turned off, and after resetting the Amp-Saver by unplugging it from your power outlet, raise the Current Sense back up slightly, and watch for the solid green Amp-Saver status LED. At this point, the Amp-Saver offers maximum protection for your tube amp and can give you advance notice if components start to fail.

My tube amp won’t turn on using the Amp-Saver. What happened?

• If the Amp-Saver light won’t turn on at all it is likely not getting power – try a different 120VAC outlet. If the Amp-Saver doesn’t light up using known working outlet, check the fuse (inside the Amp-Saver’s IEC power inlet). Note: fuses don’t usually blow for no reason – this is a good time to double check your setup for faults . Replace only with a 5A Slo-Blo 5 x 20mm fuse – there is an extra fuse held in the fuse tray.
• If the Amp-Saver light is blinking red, it has gone into ‘protect’ mode and something may be wrong with your amp. Double check your setup and see the ‘Current Sense’ section above for more information. Mercury is happy to recommend an Amp Technician in your area if you require assistance.

AMP-SAVER Consultation Services

If you are a large Manufacturer or Boutique Amp Builder with a custom AMP-SAVER application in mind, let Mercury’s Engineering team bring your idea to reality. Our experienced team is the right choice to meet your precise power flow control needs.

Article: Let’s Ask Budda with Jeff Bober of Budda Amps

Q: I’ve got an SR Blackface ’66 amp, all original. The sound is very thin, weak and trebly. There’s nothing wrong with any of the tubes, and it has been biased correctly. I’ve tried the amp through different speakers but found the same result. The amp hasn’t been played very much over the years. Can it be old, dried-out capacitors that make the amp sound like this? Can a complete replacement of the capacitors really improve the sound – meaning to give it more twang and bottom end, or “life”? – Tobbe Sweden

A: Beautiful amp. One of my favorites… except, of course, for a Budda!

I’m assuming both channels of the amp are thin and weak. If it were only one channel that sounded bad, I would tell you that the 100K resistor in the tone stack of that channel was probably open. This would also disable the Middle and Bass control, but I’m going to assume that all the amplifier controls function properly. Since you also mentioned that the amp has been properly biased, I have to assume that the primary sections of the power supply have the correct voltages.

Considering the amp’s age and the possibility that it might have been sitting idle for some time, a power-supply cap job is probably a good idea. This might not be the source of the problem, but once any other repairs have been made it will make the amp sound stronger and tighter. Make sure the values of the power-supply resistors are checked after the filter caps have been removed. A power-supply resistor that’s substantially out of tolerance can cause degradation in tone, but usually it won’t be as drastic as the symptoms you’re describing. And don’t forget to have the bias supply cap replaced. A weak cap in the bias supply will give the amp some additional unnecessary hum. You might also want your tech to do some normal maintenance on the amp, such as cleaning all of the tube sockets and controls while he’s in there. A very dirty tube socket, especially in the phase inverter, can really suck the life out of the amp. If the amp still isn’t right after the maintenance and power-supply build, it’s time to start looking elsewhere.

Okay, let’s look at some other possible causes for an anemic Fender amp. The first thing I’d look for would be the ground connections from the circuit board. These are the buss wires that come off the circuit board behind the controls and solder to the brass grounding plate that runs under the control panel. I’d check all of these connections, but there’s a particular one that seems to be the most frequent offender. It comes off the board in the area of the tremolo and phase inverter circuits behind the tone controls for Channel 2. For some reason this solder connection tends to break, causing the phase inverter to lose its grounding. That makes the amp lose substantial power and sound thin. If any of these ground connections is broken, it takes a good deal of heat to re-solder them. So, you’ll need to use a high-wattage soldering iron or gun. If all these ground are intact, the next thing to check would be the 100-ohm (brown/black/brown) resistor in this same area. It’s the only resistor in the area that is positioned horizontally on the circuit board. It also typically suffers from a broken solder connection and will yield the same low-power situation. Re-solder the resistor, and you should be good to go. If not, it’s time to start looking at the other major cause: a bad output transformer.

The best way to determine if the output transformer is bad is to simply substitute it with one you know is okay. A good way to check it is to simply unsolder the leads coming from the original transformer and attach a replacement using clip leads. If you can’t come up with a Super Reverb transformer to try, a Twin Reverbtransformer will work well for the test. If you need a replacement transformer, I have to recommend (as I have in the past) Mercury Magnetics. Their Axiom line of transformers should have just what you need. They can be found at www.MercuryMagnetics.com.

I hope you can make your Super super again.

Source: https://mercurymagnetics.com/pages/news/PremierGuitar/MusiciansHotline-2.htm

Hey Jeff,

I just finished reading your column in Premier Guitar. Great column by the way! But I was wondering if you could finally be the person to help me?

My question is, I just finished installing and wiring up a choke in place of the 400 ohm power resistor in my Peavey 6505+ head, and as far as I know it is located in the correct spot (between the screen and plate) from everyone I’ve talked to. But I must be missing something when I did this swap because when I put the head back on standby after playing it for awhile I get a “pop” when I throw the standby switch on.

Could you please advise me on just what I may be missing in this conversion to the choke? The choke is from Mercury by the way.

Thanks for your valuable time. — Scott

Hi Scott,

Thanks for your question and thanks for reading Premier Guitar.

If you installed the choke across the two terminals on the output board where the 400 ohm resistor was removed, then it is installed in the correct location in the circuit. And you are correct; this is between the main B+ supply to the output transformer and the screen grid supply. I don’t believe you “missed” anything here, but installing the choke may have changed the operation of the power supply slightly. Let me attempt to explain what I believe is happening and then pose a potential solution.

The configuration of the power supply in the 6505+, as well as in some other Peavey amplifiers, is slightly different than the standard configuration in most other manufacturers’ guitar amps. In most standard power supply configurations, when the standby switch is engaged, each section of high voltage supply powers up simultaneously. In the power supply of the Peavey, the high voltage is constantly supplied to the plates of the output tubes regardless of the standby switch setting. The standby switch simply energizes the remaining sections of the power supply. By installing the choke in place of the resistor, you have either changed the rate at which the later sections of the power supply respond to being energized or de-energized by the standby switch, or the choke is causing a spike in the power supply due to a collapsing or expanding field within the choke. You may not fully understand that explanation, but here’s the bottom line. Something is now causing a spike in the power supply and because the output tubes in the 6505+ are more “at the ready” than most other amps, they are able to reproduce this spike more quickly then an amp with a more standard power supply design. If this theory is correct and that is what’s happening, I may have a solution. It requires a bit of rewiring, but I believe it will solve the problem. Before you attempt this rewiring, please read the following disclaimer:

If you are not familiar with working around potentially lethal voltages and do not know the proper safety measures that you should take, or do not know how to employ proper and safe wiring techniques, DO NOT attempt this modification yourself. Find a knowledgeable and experienced technician.

First, trace back the two wires from the standby switch to the points on the circuit board where they’re connected. Remove the connections to the standby switch and connect those two points on the circuit board together, removing the standby switch from this point in the circuit. Next, on the side of the main circuit board where all the fuses are located, find fuse F1. Immediately to the side of F1 you’ll see two high voltage leads coming from the mains transformer. Disconnect one of these leads from the circuit board and insert the standby switch here. Either of the two leads is fine, but if you’re unsure, disconnect the lead connected to F1. Connect one lead of the switch to the transformer wire and the other end to the connection on the circuit board where the wire was removed. This will locate the standby switch at the AC input of the power supply, enabling all of the voltages to rise and fall simultaneously when you operate the standby switch. While the power supply “spike” may still happen electrically, it shouldn’t result in an audible “pop,” since the output tubes won’t be able to respond as quickly.

With the choke installation you may also notice that the amp seems a bit louder or has more gain. This is not solely due to the characteristics of a choke, as opposed to a resistor in the power supply, but it is due to the fact that the voltages in the amplifier may have risen slightly. The DC resistance of the choke is probably lower than the 400 ohm resistor it has replaced, causing voltages subsequent to the choke to rise.

There you have it. Hopefully, this will give you noise free operation of your standby switch, and we can save the Pop Phenomenon for the media!

Source: https://mercurymagnetics.com/pages/news/PremierGuitar/PremierG-18.htm

When Time runs into a dangerous power situation in an old Magnatone lap steel amp, he’s tasked with completely reimagining the project.

It seems as if almost all of our clients have at one time or another, purchased something online. Often a funky old guitar or amp that was acquired at, what seemed to be at the time, a decent price. We hear the same words uttered over and over again. I just got an amazing deal on this at e… (rhymes with hey) but I think it needs a bit of work. Often, the amount of work required to transform the instrument into something playable makes the “great deal” now seem like a thorough hosing. Sometimes items come with a trial period in which the buyer can return it if doesn’t meet his/her expectations. Other times the piece may be salvaged or kept, though unusable, simply because it has a certain amount of character that makes it worth having if only for a wall hanger.

This month we’ll be taking a look at one such project. It involves a Magnatone lap steel and amp set.

A client purchased a beautiful (and very early) Magnatone lap steel and amp set. They were brought into our shop to have a basic “check and clean” done to the amp and to have the lap steel repaired/restored. The lap steel needed to have the tuning machines replaced as the buttons had deteriorated to the point that they were now little ratty stubs that needed a pair of pliers to aid in the tuning process. A similarly styled set of Tone Pros 3-on-a-strip tuners were installed, scratchy pots were salvaged with a bit of electronics cleaner and some minor setup work was done to level the string heights at the nut.

The amplifier was powered on to see if it was working and to listen for any nasty noises that would need to be addressed in our “check and clean” procedure. Surprisingly, the amp sounded pretty darn good. It had a very unique character to the break up as the amp was pushed into distortion. The amp was then disassembled to check for leaky caps and resistors that may have drifted out of spec that would cause the voltages to swing to unsafe/improper levels. First I tried to locate the power transformer to get my bearings. Hmmmm, strange I thought, no power transformer! Then it dawned on me. This amp is running on pure AC!

While this isn’t that unusual in very early amps and it certainly contributes to its unique tone, it’s also very dangerous. One leg of the AC is tied to the chassis as a buss in the same way a ground would be in a more modern design. This would almost be okay if the instrument being played through it had the strings isolated from the electronics (though it’s still present on the metal chassis). However, in most modern guitars, the strings are attached to the ground. In this instance it means that the player now has one leg of the AC on his/her strings! This puts me in a rather precarious position. As the tech and owner of the shop, there are some obvious liability issues associated with this project.

The client was consulted and told of the dangers that lurked within this design. As he loved the look and character of the box, he gave me the go ahead to build a simple and more “modern” (late-’50s) design into the existing chassis. A promising schematic was found (a Valco of some sort) that used a 6SL7 octal preamp tube a 6V6 and a 5Y3 rectifier. This design was chosen simply because of its funky character, which was thought to be in keeping with the original design.

The build was a bit tricky as the amps chassis was quite small and was never made to carry the bulk of a power tranny. Every component was stripped off and the task of figuring out a layout that was physically possible, considering the tight space, begun. It was necessary to make a metal plate to cover a hole left by one of the tube sockets that had to be relocated to make room for the new Mercury power tranny. The output transformer had to be located inside the chassis due to lack of room caused by the speaker’s magnet protruding into the optimal space. New holes had to be drilled/punched for the input jack, transformers, IEC style AC socket and tube socket.

It’s freeing being charged with the task of simply making something funky that works. Certain liberties can be taken in component selection that wouldn’t necessarily be considered when shooting for a dead silent recording amp or a rock solid touring amp for example. I was able to use some really neat Soviet-era paper in oil caps that I found while traveling in Bulgaria last year as well as some interesting carbon comp resistors acquired at the same time. Fortunately, the original speaker was still in good shape and was reused.

Mission accomplished. The end result was a marriage between over-the-top vintage form and functionality. The amp was transformed into a safe and usable conversation piece and I’m told, gets many hours of use a week. While this project may not have been the most economical way to go about getting a small practice amp, it did end up salvaging a very cool set and making it safe and enjoyable for the proud and happy owner.

Source: https://mercurymagnetics.com/pages/news/PremierGuitar/PremierG-28.htm

Finding and restoring old amps and cabinets is a slow process that demands patience. From the time we first began trolling eBay, ultimately scoring a tweed Vibrolux and Tremolux, to final delivery of the aged cabinets and assembly of the amps, six months had easily passed.

We first found and bid on a ’58 Vibrolux in September ’06. Sold by an eBay seller in Texas, it had been recovered in reddish-brown cloth similar to the stuff used to cover hymnals or a bad ’60s pleather recliner for the double-wide. Otherwise, it was pretty straight, with the original blown Jensen P10R intact, and the original transformers, caps and resistors. The inside of the cabinet had been painted black, but the cabinet, grill cloth, baffle and control panel were otherwise intact, and the wooden tremolo footswitch was included. We bought the Vibrolux for $1,590.00 with 4 bids placed.

Inspired by Larry Cragg’s detailed description of Neil Young’s tweed Tremolux, a1958 Tremolux surfaced on eBay in November 2006, and we scored it for just $1,082.00 from a seller in San Francisco. We suppose this amp was so cheap because the output transformer had been replaced, and the cabinet had been completely stripped and stained mahogany brown. The original speaker mounting screws in the baffle board were about to fall out. However, the original Tremolux circuit was well-preserved, and a small strip of tape remained in the chassis signed in a delicate hand by “Lilly” – one of the many women in Fullerton employed to assemble amplifiers like the Tremoluxin 1958. God bless her. The Tremolux also arrived with the original wooden foot switch.

The Vibrolux kicked some serious tail right out of the box. We send the original Jensen P10R to John Harrison at A Brown Soun (www.abrown.com) for a re cone, mounting a1965 Jensen C10Q sent by Larry Pogreba in its place – a very stout choice and original equipment in early blackface Vibrolux Reverb amps. Like the Tremolux, the tremolo circuit in the Vibrolux required some TLC,with four caps needing replacement to restore the swampy oscillator circuit to full wobble-weave. We also replaced all the newish tubes with NOS RCAs, Philips and GEs. Once we had the amp mounted in the restored and aged cabinet, we were throwing down hard with our No caster nightly, wallowing in the big sound coming from such an innocent-looking little biter, when the original output trans-former gave it up in a final, glorious gasp. A quick call to Mercury Magnetics produced a ToneClone replacement within a week and we were soon back in business,sounding better than ever.

The 10 watt, 3-input ’58 5F11 Vibrolux is housed in the same cabinet Fender used for narrow panel tweed Deluxe– a fat little featherweight with greasy tremolo and a smooth bark tailor made for a Telecaster. And 10 watts may be the perfect power notch for low-volume home recording and jamming – crystal clear, bright and drenched in gorgeous Fendery overtones at low volume (3-5), and absolutely on fire from 7-10. In all respects, the 5F11 Vibrolux is a big amp in a small package worth pursuing for its outstanding tone and personality at truly usable volume levels.

We were amazed by how Gregg had managed to remove every trace of black paint that had been sprayed inside the cabinet, and his aging job, complete with three coats of amber stain and lacquer, faint water stains along the bottom,worn seams and corners, aged L&L leather handles and scorch marks from the power tubes on the inside of the back panel were flawlessly conceived and applied. Hopkins even recreated the original tube chart with a 1958 date code after requesting that we send him the chassis number and power transformer EIA code for production verification. When we brought the restored Vibrolux to Jeff Bakos’ shop (www.bakosampworks.com), he looked it up and down as it sat on the floor of his workshop, peered into the back and said, “That is totally sick.”

The ’58 Tremolux provided a further study in what can be involved buying 40 year-old amps. Upon arrival,the amp was really smokin,’ even with the Jensen hangin’ off the baffle board. The tremolo was DOA, however, so while the stripped cabinet was getting the spa treatment in St. Louis, Jeff replaced two caps in the trem circuit, we replaced the already replaced output transformer with another from Mercury Magnetics, and stored the chassis away until we received the finished, aged Tremolux cabinet from Gregg in late March ’07.

The 5E9A (’55-’56) and 5G9 (’57-’60) Tremolux are housed in the same taller, wider cabinet Fender used for the 1×15 narrow panel tweed Pro,and the later 5G9 circuit is quite different from both the 5E3 Deluxe and the ’55 5E9ATremolux, being fixed rather than cathode biased, employing a long-tailed phase inverter common to the bigger narrow panel tweed amps, and the addition of an extra filter cap and choke enabled the power to be increased from 15W to 18W in 1957.

Compared to the narrow panel tweed Deluxe and the 5E9 Tremolux, the 5G9 Tremolux develops more volume and headroom, and should you chose to replace the 12AY7 preamp tube with a 12AX7, gain is further increased (it’s already righteous with the 12AY), while the bigger 10” x22” x 10” cabinet produces a much rounder, warmer tone with superior ambience and presence. In the month or so since we’ve had the Tremolux put together in the restored cabinet, a new Tung Sol6V6 blew (after we had opted not to use a couple of spare ’50s RCAs for safety – they are in the amp now and killin’ us with bogs of good thang),and we just took the amp back to Jeff when it began spitting some nasty distortion provoked by low frequencies from the guitar. Turned out to be a few bad solder joints.

Like the Vibrolux, Gregg had stopped short of creating a “3-legged dog with an eye patch,” taking the aging to a moderate level with frayed edges and seams on the amber tweed, a single beer can ring on the top with a foam overflow stain running down the grill cloth, a slight orange stain on one side from pine knot bleed, and assorted scuffs and light abrasions. He also repaired the baffle-board, filling in the old holes for the speaker mounting screws.

We hate doing this to you (again), but truth be told, we have to give the nod to the Tremolux as the most toneful and inspiring amp in its power class (18 watts)that we have ever heard or owned. It’s ascension to Numero Uno status was a bit of a surprise, but then again, we considered the initial source of our inspiration for finding one – Neil Young, via his tech, Larry Cragg, and in hindsight we should have expected as much. With all the attention paid to the tweed Deluxe as the big time bonerizer of the tweed family, the Tremolux seems to have been overlooked for the usual reasons…. In the nose-to-butt-crack daisy-chain march to mediocrity, the masses never seem to acquire a view beyond the first lazy dumb-ass directly in front of them. In the immortal words of the great hoosier educator and smack-down artist Earl Dosey, they are “stepping’ over dimes to pick up nickels.” Let’s hope the lemmings continue to keep their heads down.

So here’s the move…. Sad as we are to share this, our strategy was as obvious as it seems. Forget about original speakers, don’t let a replaced tranny run you off (we’ve never replaced one with a Mercury that didn’t sound better than the original), and deliberately track down the fuglies told girls you can find from the tweed era. Busted baffle boards? We luv that….Ricky-ticky cabinets are good, and the coverin’ don’t matter. What you want is a beater with a totally neglected chassis and as many of the original fat Astron caps and original resist or present as possible. Yeah, some of them may have to be replaced, but it’s far better to allow a prudent and judicious amp tech determine that rather than buying an old amp that has been raped by a hard chargin’ cowboy hooked on Sprague Orange Drops.Buy one of those and your old amp will sound new,never to sound old again, and that’s most definitely not the play you want to make here. A little component drift is good.

There is luck involved, too… not all vintage amps were created equal. Some of them left the birthing bench endowed with incredible tone – a happy accident created by the melding of variable components that resulted in extraordinary sounds. Others were created by the same roll of the dice, but with a different outcome altogether – mysteriously dull, flat, or simply lacking whatever you wish to call it… that tone, mojo, bloom, the harmonic complexity of your first Schlitz, depth, fatness… whatever. To experience the blissful afterglow of unanticipated discovery, you must be willing to risk something, which is another way of saying that faith must be exercised in the absence of a guarantee. In this respect, buying old amps is a lot like life itself…. The greatest obstacle to discovery is the flawed perception of an impossible challenge. And the window of opportunity is closing on these great old amplifiers faster than you may think. Like vintage guitars, the best old amps are being taken out of circulation by col-lectors willing to pay prices that are based on potential future value (more than they are worth today, perhaps, but less than they will be worth tomorrow). For you, hombre, the time to bust a move is now.

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By now, you’re probably familiar with the Epiphone Valve Jr., the tiny, low-wattage, low-budget amplifier that hit store shelves a few years back and single-handedly energized a cadre of amp modders, so we won’t go into a cursory rehashing of its history. But it should be said that the amp’s simplicity — demonstrated by the lone chicken-headed volume knob that flies in the face of modern complexities — has since combined with a growing, gear-obsessed online culture to create a technological phenomenon. Like muscle cars in the sixties and Superstrats in the eighties, people are again obsessed with hot-rodding, and the Valve Jr. can be viewed as a major driver of that shift.

With modification tips spreading like an unrestrained virus through message boards and forums, facilitated by the tone-seeking faithful, it was only a matter of time before established companies caught wind of what was going on. One of those was Mercury Magnetics, an outfit best known for conceiving badass power and output transformers for a variety of modern and vintage amps. They wisely realized early on that the amp’s blank slate vibe would provide the perfect showcase for their talents. Mercury’sSergio Hamernik and L.A.-based amp wizard Alan Cyr went to work designing a custom set of transformers and choke for the diminutive Valve Jr. — a project that, ironically, was originally intended simply as a transformer demonstration kit.

Transformers & You

Having been intrigued with the amp’s possibilities since its conception, we’ve tested out a variety of modifications, from the homegrown (see Dirk Wacker’s web exclusive columns at www.premierguitar.com) to commercial projects, such as the popular BitMo modification kits (reviewed in October 2007). For the most part, they’ve all added some usable capabilities while maintaining the original vibe of the amp — mainly, stripped down rock tones with passable tube warmth. But while most of these mod projects have expanded the tonality and scope of the Valve Jr., none have completely changed it. Mercury Magnetics’ Epiphone Valve Jr. Kit is likely the only one on the market that can make that claim.

The basic gist of the modification kit involves the installation of new power and output transformers, the addition of a choke — a rarity in budget amplifiers these days — and a basic reworking of the amp’s circuitry to eliminate some of the noise and hum that plagued early models. And while opinions in our office were divided over the amp’s new sound — the amplifier’s single-ended tonality became more pronounced, and highlighted some of the weaker links in the signal chain, including the stock speaker — there was absolutely no denying that the amp had an expanded tonal range that was unheard of in this price range. With more consistent power flowing into and out of our Valve Jr., there was more of everything. The lows became instantly tighter, the highs shimmered and the entire spectrum of sound now had a beautiful fullness. As that single volume knob rotated clockwise, the Valve Jr. bristled and growled like a Rottweiler about to lunge. This thing had a newfound set of marbles and I, for one, was not complaining.

We should note that our Epiphone’s sudden meatiness did not come easily. The kit’s instructions, included on a CD-ROM, seemed conceived not by English majors but by engineers, consisting of a lengthy PDF file filled with close-up photographs instructing users to copy what they see. To the company’s credit, the photos are well done, providing enough detail in each shot, but more text would have been helpful for those of us who aren’t the best at spatial learning. In fairness, we received an early version of the manual, and Mercury Magnetics has said that a much more complete, easy-to-navigate version is now available.

“The basic gist of the modification kit involves the installation of new power and output transformers, the addition of a choke — a rarity in budget amplifiers these days — and a basic reworking of the amp’s circuitry….”

While the clipping and wiring of resistors and leads may be feasible for most readers, this project also requires some advanced know-how like cutting traces and drilling holes in the PCB. New entrants to the amp mod game will quickly find themselves in way over their heads, and might want to consider some of the other mod options available if they are set on doing it themselves. In the spirit of complete disclosure, we got through the first few steps before we were forced to hand the project over to a local amp tech. It cost a few more bucks in the end, but the results were absolutely worth it, giving us an amp that we could record with, or even take along to small gigs. And who saw that coming?

The Final Mojo

Put into a strict cost/benefit matrix, products like the BitMo might come out as the better deal for the weekend modder looking to push the Valve Jr.’s envelope. The work and price involved with the Mercury Magnetics kit might seem like a large compromise for some groups — you could take the money you’d spend here and put it towards a higher-end amp, like Orange’s Tiny Terror, without spending days etching lines in a PCB. But those people are not who this kit is aimed at — this project is meant for those amp tweakers that dream of turning a drab, utilitarian piece of equipment into a snarling, steroid-infused monster, no matter the cost. And for these guys, this kit will be both intrinsically rewarding and positively orgasmic.

Source: https://mercurymagnetics.com/pages/news/PremierGuitar/PremierG-11.htm

It’s truly amazing that half-century-old amplifiers are still out there, churning out more ear candy on a daily basis. But perhaps even more amazing is what you see if you peer inside the back panels of these warhorses. Some look so weathered, dusty, and rusty; you wonder how the hell they still work! Even more impressive is that most of these amps, with very little service, sound as good or better than the day they rolled off the production line.

How is that possible? Well, we know speakers get better with age and use, and old tubes are da proverbial “bomb.” Some might go so far as to say aged wood in a speaker cabinet adds flavor to an amp’s tone. But when you look at a rusty old transformer—pitted, flaking, and by all appearances a fire hazard—you get nervous because that transformer’s just gotta be on its last leg, right? Like, any instant now, there’ll be nothin’ coming out of it.

That perception inspired Mercury Magnetics’ Sergio Hamernik to devise an experiment to see whether rust affects the transformer in a guitar amp. His results might surprise you….

VG: So, is rust bad for a transformer?

SH:I can understand how one can be tone-sucking in nature. One of the obstacles to getting the best tone out of transformers is to minimize those losses.

VG: So, are all transformers prone to rust, or is rust a sign that a transformer was cheap or poorly made?

SH:Rust can actually be a mark of quality on a transformer, because better grades of iron rust fairly easily.

VG: So, how did your experiment work?

SH:We did an A/B comparison on identical transformers. One was left outdoors for seven years,exposed to the weather, cobwebs…you name it! The second one, from the same production—samemachine winder, etc.—was put away pristine, without a speck of rust, for the same seven years.

We put both on the bench and subjected them to a battery of true A/B tests,showing them the same input voltages. And we intentionally left the output leads unconnected so we could measure each transformer’s performance without outside influences.

VG: The result?

SH:The rusty transformer ran at a lower temperature because it drew less power. Bear in mind that each transformer started life drawing the same power! At the very least, the results show that rust didn’t harm the performance of the transformer. And they imply it actually helped a little. So, if you’re worried about rust affecting the performance of the transformer in any of your amps,don’t. If you simply don’t like the way it looks, don’t sand it off! Instead, seal it with varnish, but make sure the varnish is completely dry before powering up the amp.

VG: Does the change rust causes in a transformer’s efficiency change the sound of the amp? Or does it just make for a more efficient transformer?

SH:If there’s any shift at all, it shifts toward helping the tone, not hurting it. The same holds true for output transformers. We’ve had more than a few rusty output transformers in amps with the most amazing tone.
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We told this was coming.. Tes, when readers ask us to review something, we do our best to respond, and thanks to RedPlate founder Henry Heistand, we received two RedPlates for review. We’ll start this episode by telling  you that Henry Heistand appears to be a very clever fellow who is not working in the shadows of that past, which is to say that he builds feature-rich amplifiers that in no way pretend to be vintage knock-offs. Play a RedPlate and you’re firmly treading in the present, rather than mining tone out of a dusty box built by a dead man (or woman—sorry Lily). And that’s fine. There is certainly ample space in these pages for the living, and RedPlates are in fact very lively tools indeed. We asked Henry to give us a glimpse into his background and motivation, and our reviews of the TweedyVerb and BlackVerb follow….

TQR: How and when did you initially become involved in electronics and amplification?

HH: Starting around age 12 playing to the radio and jamming with friends, my first build attempt was a speaker cabinet made out of ½ plywood and covered with yellow carpeting. It had a leopard (spotted) grill cloth and contained 6 speakers recycled from various old TVs and stereos. My first real amp repair was replacing a screen resistor in a Fender Bassman in 1970. I went to college for a year and then played guitar full time until 1979 when I attended electronics school (they still taught tubes). To pay for school I got a part time job at a church organ repair shop that had a “combo” repair department and still played in club bands on weekends. Attending electronics school in the morning and repairing gear in the afternoons was a great way to instantly translate the classroom to the real world. Compared to the tube TVs and tube broadcast transmitters, the tube musical amplifiers were relatively simple. Besides Fender and Marshall, tube amps by Sunn, Ampeg, Gibson, West, Park, Hiwatt, Sound City and all the Supro/Kalamazoo/Dan Electro stuff. If I only had a nickel for every good tube I tossed in the trash back then. Many of those same companies had solid-state amps too along with companies like Acoustic, Kustom, Peavey, Randall, Lab, SG and Roland. It seems like the ’70s was the golden era of guitar amp designers. Although most tube amps have a similar topology, the differences between brands in those days ranged from truly innovative to laughable. On a few occasions when a solid-state repair would come in that was totally fubar, one of the church organ repair guys would show me how to design a new circuit right over the top of the problem area, teaching me the value of having a few simple circuit designs at the ready for emergencies. In late ’82 I got a career job in the computer field, and by ’86 purchased the part of the church organ repair shop that repaired the “combo” gear. The new company was named Music Mechanix and kept the warranty contracts with all the majors for amps, keyboards and P.A.s.

TQR: As you became more familiar with various amp designs of the past, what were your favorites and why?

HH: Thinking back to the tonal memories accumulated during those years spent repairing amps, the most musical of all of them were probably the early ’60s Fender tube amps. In addition to repairs, Music Mechanix did all the popular mods of the day (anyone remember the original Train Wreck Mod pages for Fenders?), many times we would redo almost everything inside but keeping the exterior unchanged. Most of my playing back then was strictly radio cover songs so the quest was always to find the one amp that could imitate everything. Music Mechanix was continuing the warranty station status from the previous owner (established in the ’50s) so every original manufacturer’s amplifier schematic ever released was available as a reference source, residing in 16 large file cabinets. On the side, I kept a little notebook of circuits and mods of interest to use as building blocks.

TQR: Can you describe the lasting impressions created by your study of the experiences with classic amps that have most affected your own design philosophy and preferences?

HH: As a service to friends and regular customers Music Mechanix would take a classic amp (at the time it was easy to get something like a used Bassman for $100) and do Frankenstein amps that were Fender this, Marshall that, with a sprinkling of Vox and Ampeg thrown in depending on the customer’s needs. On the weekends I was doing gigs using a pair of modified Ampeg VT-40s in stereo until somehow I ended up with a Mesa Boogie S.O.B. that had a really innovative phase inverter section controlled by a “LIMIT” knob. A bizarre variation of a PI section’s constant current source, the circuit was not in the RCA manual or on any other schematic. It sparked something in me and from hen on I started doing creative amp mods that were not copies of things I had seen on schematics.

TQR: When did you first begin to sketch out the concept for RedPlate amps, and what did you want to accomplish that would be unique and different?

HH: I had always been fascinated with “sleeper” amps that looked small but sounded big. After selling the repair business I used my free time to do a lot of experimentation on point-to-point builds in a Fender Camp sized chassis, eventually working out how to do a 7 tube, large transformer build in a Champ chassis without noise or oscillation. My favorite guitar tones were the recorded sounds of the Mesa Boogie/Dumble ODS type amps (even before I even knew what a Dumble amp was). A clean singing tone with a hint of character that sustains and blooms is my idea of the ultimate tone and the design goal of all the RedPlate models.

TQR: Can you briefly describe the unique features and differences among the current line of RedPlate models?

HH: RedPlate probably has too many models because we treat the sections as modular building blocks. We start with one of the 3 chassis sizes:

CH1. 15” width with four 9 pin sockets and two 8 pin sockets, transformers up to the 50 watt size.

CH2: 17” width with six 9 pin sockets and two 8 pin sockets, transformers up to 80 watt size.

CH3: 19” width with five 9 pin sockets and four 8 pin sockets, transformers up to 160 watts

Then we use different combinations of the building blocks with the only limitation being the number of controls (physical knob space) and the number of tube sockets available. Building blocks currently in use:

BB1. PREAMP1—Tweed—A single tone knob preamp (Tweed style).

BB2. PREAMP2—Blackface—A Treble, Middle, Bass Preamp (Blackface style).

BB3. DRIVE1—A three knob overdrive section (Gain, Drive, and Level).

BB4. DRIVE2—A six knob overdrive section (Gain, Drive, Level, Treble, Middle and Bass).

BB5. REVERB—A single knob tube reverb with medium decay tank.

BB6. EFFECTS LOOP—A fully buffered serial loop, return level is the master volume.

BB7. PHASE INVERTER—Standard Long Tail pair, very similar to the early ’60s designs.

BB8. POWER AMP #1—40 watts cathode bias (6L6GC).

BB9. POWER AMP #2—50 watts fixed bias/40 watts cathode bias (6V6GC)

BB10. POWER AMP #3—80 watts fixed bias (KT-88).

BB11. POWER AMP #4—45 watts fixed bias/18 watts cathode bias (6V6GTA)

BB12. POWER AMP #5—100 watts fixed/50 watts fixed (6L6GC).

TQR: Both of our review amps are loaded with Warehouse speakers from Kentucky, which we have reviewed before. How extensive are your evaluations of various speakers when creating a new model? Does the same process apply with transformers, tubes or other components?

HH: The current lineup is using WGS Retro 30, WGS British Lead 80 and Eminence Swamp Thang speakers in the combo amps. The decision to use these was based on side-by-side comparisons with other brands (an ongoing process).

Tube selection is mostly based on reliability (as long as the tone is still there). The current production amps use Svetlana 6L6GC, SovTek 12AX7LP (PI tube), and Electro Harmonix 6V6GTA and 12AX7s (preamp).

Selecting individual signal path components is more difficult because side-by-side comparisons can be misleading (no 2 amps are exactly alike). The signal path in current production amps use PS series Orange Drop capacitors and carbon film resistors based on low noise and musical warmth in the tone. RedPlate Amps has a good relationship with Mercury Magnetics and I like to use their transformers in most models.

TQR: How does the half power switch function in your amps, as well as the “mode” control and various voicing controls?

HH: Depending on the output section, 3 methods are used:

1. 6L6GC 100 watt/50 watt—The switch lifts two of the four tubes by 10K so they are effectively out of the circuit yet the impedance selection is still valid.

2. 6V6GTA 45 watt/18 watt—Full power runs two of the tube in cathode bias and two in fixed bias, the switch lifts the fixed bias tubes by 10K to effectively remove them without changing the output impedance.

3. 17 Watt (Hi/Lower)—This switch just lowers the voltage to the phase inverter tube so the amp breaks up sooner. There are two different styles of mode switches. On the Tweed style preamps the 6 position mode regressively reduces midrange and preamp output to imitate a Blackface style amp. On the Blackface style preamp the 6 position mode switch progressively fattens the midrange to imitate a Tweed style amp. Most of the models also include a Humbucking/single coil switch to set the amount of bass gain in the input stage.

TQR: How much individual customization or voicing do you offer for specific models when working with an artist?

HH: Unlimited customization is available, although most of the professionals that use RedPlate Amps are content playing standard models.

TQR: We noticed that you include the owner’s name on the back panel, correct? A nice touch…

HH: Yeah, the front and rear panels are done in-house, we could even put pictures of your dog on there.

TQR: What do you want to accomplish in the future? New models?

HH: “Amps that sing” being every guitar player! Going forward, curiosity and customer feedback will continue to drive the evolution of current designs and the development of new designs. For example, there will be a “shredder” amp in the near future (The ShredPlate) and possibly a bass amp. As RedPlate continues to gain name recognition with the music industry, models like the BlackVerb, MagicDust and TweedyVerb will hopefully be taken for granted as standard amplifier types.

The front and rear panels on the BlackVerb reveal an impressive array of controls, push/pull-knobs and switched pots. In fact, the printed operation guide includes a signal path diagram on the front page with a welcoming invitation to skip an in-depth review of the manual and just set all the knobs at 12 noon and play, which we did, consulting the manual as needed as we spent more time with the amp. So, is the BlackVerb too complicated for you “plug & play” guys? Not really, but the control panel is best reviewed in sections. You’re essentially working with a clean preamp circuit and a Drive section that includes Gain, Drive and Level controls for variable levels of distortion overdriven tones, but there are still many more additional tweakable features lurking within…

The first control adjacent to the single front input jack is the miniature Bright switch toggle with the center position OFF, Down producing the sound of “new strings” (an accurate description we might add), and Up rendering a brighter tone that will be familiar to those of you with a Fender Blackface amp with bright switch. We usually use the bright switch to put a little extra shimmer and spank on humbucking pickups, or neck pickups on single coils.

The Volume control includes a pull switch to engage a midrange boost that increases upper mids. The Middle control does what you’d expect, with a pull switch for a “Deep” setting that scoops mids and boosts bass frequencies—an excellent change-up for clean tones. The Bass control handles low end quite well, and it can be clicked OFF to be removed from the tone stack. Try that with a neck pickup and it produces the odd and very different EQ found in some old Valco and Gibson amps.

The Mod Selector is a 6-position rotary EQ switch that gradually produces a fatter, thicker tone as you rotate left to right from the “Funk” setting, to “Normal” and “Fat” (tweed). All this pulling and turning may sound complicated, but you’ll have it thoroughly digested in 5 minutes, and most importantly, these extra EQ controls expand the tonal capabilities of the BlackVerb in a clever and creative way that really is worth using and exploring. We have bitched about such bells and whistles on other amps having limited value, but no such questionable affectations plague the BlackVerb. Like we said, Henry is a clever fellow. On the Drive section…

This is where you mine and manage overdriven tones and distortion. The Gain control can be bypassed by clicking fully left, otherwise, you’re setting the amount of signal being sent to the first gain stage, which produces variable levels of smooth growl and grunt. The Drive control further ramps up distortion through two gain stages, and a pull switch on the knob serves as an afterburner for maximum burn and rip. At this point you will be channeling Metallica at full husky, so hide the dog. The Level control sets the output volume for this section, resulting in a progressively bigger, thicker, bolder voice. Of course, the big selling point for the BlackVerb is how all of your clean, moderately busted up and filthy dirty tones can be deftly tweaked and the volume managed with the Volume and Master volume controls. At the full power setting, you really can get this thing to sound like a 100 watt high gain amp on “7” at low decibel levels suitable for home recording and friendlier sound pressure levels.

The reverb control is what it is, and you can turn it off fully left and it’s out of the circuit. The Presence control is described as using “global negative feedback to remove low frequencies which frees up bandwidth for more midrange and highs,” and it can also be turned off when rotated fully left. Frankly, the appeal of this control escaped us, but we can imagine how it might be useful in a live situation where you may want to avoid too much low end muddying up the mix with bass and drums. The Master volume works very well without producing the dreaded master volume/low volume faux zizzz when you’re trying to light a fire at low volume levels.

One of our favorite features is the 50 watt/40 watt switch on the back panel that changes the boas from fixed to cathode for a completely different feel. With the 40 watt cathode biased setting you can also change the 6L6 output tubes to 6V6s, transforming the BlackVerb into an 18 watt cathode biased flame thrower, or bypassing the Gain section for a more tweedy character and voice. The Hi/Lo power switch changes the voltage on the input stage and the threshold for clean headroom.

The back panel Smooth switch is just that, adding slight compression in the clean preamp, and the Humbucker/Single Coil setting sets the amount of bass gain in the input stage, relieving you of perhaps resetting EQ when switching from single coils to humbuckers.

Additional utilitarian features on the back panel include a handy bias adjustment and test point, speaker impedance selector, main and extension speaker jacks, FX send and return, and footswitch jack. The footswitch gives you the capability to get in and out of the Tweed, Drive and Boost circuits. Tweed boosts upper mids while lifting the midrange control on the front panel for maximum push in the frequencies where the guitar really lies on stage. Drive engages the Drive feature, bypassing it when off at the footswitch. Boost makes everything sound bigger with a partial tone stack lift.

And now for the bottom line…. It seems to us that the intention of the BlackVerb is to be as tonefully versatile as a 1×12 combo amp can possibly be whether you are playing small clubs, bigger rooms or wide open outdoor stages. You could play nothing but smooth, clean jazz through this amp without ever venturing into the gain stages and be perfectly happy. Or you could do nothing but feast off the considerable gain and distortion lurking in the heart of the BlackVerb and be equally happy. Most gigging musicians want to range between such extremes living somewhere in the middle, and you can do that, too. Like most feature-rich amplifiers, you’ll find certain favorite settings that will be revisited with specific guitars, and after a few days you’ll have no trouble quickly accessing those settings, although the control panel is a bit difficult to read until you no longer need to read it at all.

The standard Warehouse Retro 30 speaker is a brighter version of the Veteran 30 we have favorably reviewed in the past. Given the considerable range of overdrive and distortion available in the BlackVerb, the Retro 30’s clear, articulate character and exceptional capacity to handle low frequencies makes it an excellent choice for this amplifier. Even at extreme gain and drive settings, the BlackVerb produces a rich and musical burn that does not mask or obscure essential overtones and harmonics. The clean tones are equally strong, powerful and clear, and the amp will nimbly spill into overdrive played clean at higher volume levels that can be managed with the volume on the guitar. The BlackVerb impressed with its ability to embody many different styles of amplifiers in one compact box, limited only by your capacity for experimentation and your imagination. Imagine that.

We were particularly anxious to experience the TweedyVerb because it seems to fit the power and volume requirements of so many players today, and it is a very straightforward and versatile 1×12 combo that is a breeze to hump to the next gig. Got your attention there, did we? We finally figured out why vintage blackface Pro Reverb amps have remained relatively underpriced… just pick one up.

The TweedyVerb is a cathode biased dual 6L6 amp with reverb, loaded with an 80 watt Warehouse British Lead 12” speaker. You won’t find a bad tone in this amp, and the controls are very intuitive, delivering outstanding “blackface,” “brown” and “tweed” tones via a 6-position Mode switch. The Bright switch is identical to the BlackVerb (you’ll love the “new strings” setting), with a single Volume control, simple Gain control, and a Tone control that can be clicked off fully left to bypass the tone stack for a very heavy and thick does of overdriven tones with excellent dynamic feel and touch sensitivity. The spring reverb is good—delivered form an original new old stock Accutronics pan made by Cary, IL, and the Presence control is identical to the BlackVerb, using global negative feedback to remove low frequencies and emphasize mids and highs. It also seems to decrease volume and gain, best used in our opinion for clean tones.

The 40 watt/17 watt switch on the back panel changes the voltage on the phase inverter. We preferred the sound and girth of the 40 watt setting, which still allows plenty of room for managing volume and variable distortion with the Gain and Volume controls, but the 17 watt setting is fine, too for close quarters. 6V6 power tubes can also be used at this setting without re-biasing for lower power output and volume. A footswitch is included to access both the fat Tweed setting on the Mode switch on the fly, and the Boost function, which acts as a tone stack bypass. Despite its compact size and relatively light weight, the TweedyVerb is a big-sounding amp that produces outstanding clean tones at usable stage volume, yet it can also be gradually pushed into the familiar sound of a Deluxe Reverb on “6” or even a vintage Marshall head at higher volume and gain settings. It’s a right fair chameleon, this one.

The Warehouse 80 watt British Lead 12 gracefully handles the power output of the TweedyVerb with excellent clarity, sold bass, vivid mids and a sweet and chimey top end. Like the BlackVerb, the TweedyVerb offers the sound and feel of several distinctively different amps in one box via the Mode switch, and we liked them all, from the rough and tumble Tweed, the slightly less raucous, smooth upper mid voice of the Brow, and the more scooped, open and airy Black settings. Both RedPlate models reviewed here clearly share the same DNA, which is to say that they possess a remarkably rich and music character, whether you choose to stroke big clean tones through them or dial up a tone that would make Billy Gibbons proud. Douse that light, and Quest forth….

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I’m a player from Los Angeles. Even though I endorse companies like Framus and Brunetti amps, who both make fine equipment, I still rely on Marshalls for some of my favorite tones.

Last month I went on a quest—how can I make my “road-dog” amp, a Marshall JCM DSL 2000, play like my vintage 30+ year old Plexi (which stays home, of course!)?

Well, first I got a tech to change a couple little things: resistors out from the volume pot, a couple of changes with the EQ resistor’s values, etc. This made a bit of difference. Then I played with a variation of power and preamp tubes, from different companies (GT, JJ and Tesla) until I found the combination I liked best. This made a perhaps 25% difference. I was happy, but still searching for that missing ingredient because the Plexi had… well, more of everything, including more power, more clarity, faster response and fuller overall frequency. So, I kept fishing around on the web and by chance hit upon a review for Mercury replacement transformers.

As luck would have it Mercury is located 5 minutes from my home! I thought I had nothing to lose by replacing the transformers since it’s usually a fast and easy tech operation, so I went to see them.

Along with their technical knowledge, what struck me instantly was their level of care and enthusiasm. Mercury’s Sergio Hamernik explained that I could do more than upgrade the existing power and out-put trannies, such as add a real choke to the circuit, like the original Marshalls(the stock DSL has a cheapy resistor instead of a choke).

Although Mercury had something special in mind, I had a gig in a couple of days, so we decided to only replace the output tranny (OT)—then finish the job later. Not all transformers are the same within any model (or year) of amplifier, and in many cases there are radical differences. Mercury makes a particularly outstanding drop-in output that would help the JCM’s sound. Although it was a temporary “patch”this change gave me the chance to feel, let me repeat, f-e-e-l the amp at my gig, and I was positively surprised by the how it reacted and sounded. Simply stated, the improvement with the feel and tone was 50%. After the gig Mercury went to work on my amp by liter-ally re-engineering new power and output transformers specifically for the DSL. The power transformer(PT) utilizes their new “SuperStack” technology (it’s huge and looks like a skyscraper in there!) that completely eliminated the amp’s tendency to overheat! They also modified the circuit by adding a choke. The final result was nothing short of a revelation! The amp has more power, better tone, faster response, wide palette of frequencies… it has more of everything!

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Decades ago, practice amps were effectively no-frills versions of their bigger brothers. Even so, those little amps of yesteryear became something magical in the studio. From Jimmy Page and his Supro to Joe Walsh and his Fender Champ, getting big sounds from little amps became the stuff of legend and a go-to approach for recording. Crimsontone Amplifiers embraces this philosophy in a big way—only two of the seven amps the company offers are 20 watts or more. Their newest amp—the 4-watt SE Mini—is a testament to the power of small and a cool nod to the role of low-wattage amps in the history of rock ’n’ roll.

In the Court of the Crimson
At just 7.5 pounds, the SE Mini certainly lives up to its name. The cabinet is covered in a tough red tweed fabric, and it features a sporty aluminum handle for easy transporting to the studio—or a gig in the park for that matter. Crimsontone didn’t design the SE Mini with gimmicks in mind either, which is evident in the simple feature set. It has just four controls—Gain, Tone, and Master knobs, along with a tiny Gain Boost switch.

The single-ended, all-tube head is powered by a Sovtek EL84 coupled to a JJ ECC803 preamp tube and a Mercury Magnetics GA5-P power transformer for a maximum of four watts. The GA5-P is part of Mercury Magnetics’ fantastic Toneclone Plus line, which is stocked with the company’s replicas of famous power transformers from the past. In this case, it’s a faithful reproduction of the transformer in Gibson’s 1950s Les Paul Jr. combos. I was pleased to see that the output transformer was also a Mercury Magnetics model, an FTCO-M that replicates the units in Fender’s Tweed Champ amplifiers of yore.

The SE Mini doesn’t rely on modern circuit design, but instead forgoes current technologies for a traditional, handwired, point-to-point circuit. Upon pulling out the adorably small chassis, I was treated to the sight of tidy wiring held together with clean solder joints and tight mounting. And the Components—F&T filter caps, Alpha pots, Orange Drop capacitors, carbon-comp resistors, two Xicon power resistors, and a Cliff input jack—are all top-of-the-line.

Good Things … Small Packages
Crimsontone touts the SE Mini as a practice amplifier, but it excels at hitting tones in the ’60s classic-rock vein. With a Fender 60th Anniversary Telecaster and a feed to the two 12″ speakers in a Fender Twin Reverb reissue, the Crimsontone’s clean mode belted out seriously raw, garage-rhythm jangle with a dash of classic Neil Young sting thrown in. The highs are crisp and brash, with tight lows and a gritty midrange. With a Gibson Les Paul Studio, the amp accentuated the midrange and softened highs, but the amp still retained its bold essence, staying tight in the low end and having a nice, even sag. It’s not a sound for everybody, but it speaks in the raw, unadulterated tones of no-holds-barred slingers of the first classic heavy rock era.

It’s worth noting that, while the SE Mini kicks with James Gang-worthy tones, I did have to really work with my picking hand to squeeze any real dynamics out of it. That said, that’s not uncommon with most small-wattage amps, and it certainly doesn’t mean that the amp isn’t touch sensitive. But if you’re used to using a big Marshall to get your ’70s tones, the SE Mini will feel like an entirely different animal. The amp doesn’t have excessive gain or saturation to hide behind, so it assures that you hear every single mistake. The sweet sounds that come as a trade-off are well worth it, though.

This Dog Bites
Getting the most meat and bite out of the SE Mini requires careful adjustment of the Gain and Master knobs. With the Gain Boost switch off, not much grit is available from the Gain control. Rather, it acted more like a voicing control, altering the feeling and response of the tone. Most master-volume tube amps have a gain structure that changes from tighter and crisper to warmer and spongier as you increase the Gain. Without the boost on, the Gain control on the SE Mini reacts the same way, but without adding huge amounts of saturation. Kicking in the Gain Boost adds a dose of rage to the tone, and I thoroughly enjoyed playing quick double-stops and soaring country bends with the SE Mini’s overdrive-infused, high-midrange snap.

Predictably, the boost kicks up the volume a few decibels, too. And I discovered by lowering my guitar’s Volume knob just how well the amp cleans up at even the dirtiest settings. The Gain Boost adds noticeable touch sensitivity, too. I got one of my favorite tones by dropping the Telecaster’s Volume down a quarter of the way and letting my picking-hand attack determine the amount of overdrive.

If you’re looking for more aggressive tones, it also pays to keep the Master at or near its highest levels. At practice-amp volume levels, the Telecaster sounded a little thin, and understandably so—I wasn’t pushing the single EL84 enough until I moved the Master to 3 o’clock, where there was a considerable volume jump. The sweet spot on the SE Mini’s Master is just a little higher, where it retains just the right amount of definition, while maintaining ample punch. Set the Master there and use the Gain control to set the flavor of the attack, and you’ll find a load of tone variation at your fingertips. Working within this range helped me keep the Tele’s bite under control and let the raw nature of the amp’s voicing shine through.

The Verdict
Four watts may not be the right recipe for tearing the paint off walls, but the SE Mini uses a well-designed circuit and quality components to sound much bigger than it looks— especially with a few 12″ speakers at the receiving end of its signal. Crimsontone’s SE Mini is a great choice for lovers of dirty, jangly rock guitar tones. But, like tube practice amps of yesteryear that needed to be driven and played hard to achieve their fullest tonal potential, it can require a more dynamic and forceful touch to tap into its inherent dynamics. Still, there’s nothing quite like a healthy, low-watt tube amp cranked to high heaven for creating sweet, raw, rowdy sounds. In that musical category, the SE Mini is a hit.

Buy if…
you’re a fan of dirty, to-the-point guitar tones at reasonable volumes.
Skip if…
you need to be heard over a drummer or can’t abide bone-simple feature sets.
Rating…

Street $799 – Crimsontone Amplifiers – crimsontone.com

Source: https://www.premierguitar.com/articles/Crimsontone_SE_Mini_Amp_Review

Hey, you guitar players… don’t think for a minute that you should skip the following articles because they are too technical. You’ve dropped some big money over the years on your guitars and amps, right? Transformers are the very heart of every amplifier, and your output transformer can influence your tone every bit as much as your choice of pickups, tubes, and speakers. Our attention was recently focused on output transformers after one of our all-time favorite “keeper” amps, a blackface Fender Pro Reverb with an amazing pair of Jensen Vibranto speakers went down with a bad output transformer. (By the way, Pro Reverbs remain some of the best vintage bargain tone machines every made, and why they have failed to receive the high praise and prices reserved for blackface Super and Deluxe Reverb amps is mystifying. Get yours now.) Cesar Diaz kindly sent us a new Mojo Tone replacement OT, and it was immediately apparent to us that although we had always considered the tone of our Pro to be extraordinarily good, things had improved significantly after installing the new OT. The amp had more punch and power with less sag, and that got us wondering if output transformers could slowly decay over time, subtly sapping the full potential of a great amp. We concluded that it can, which led us to consult with a couple of experts on the topic of guitar amplifiers and transformers. We asked Victoria Amplifier founder Mark Baier (aka Sam Bisbee) to comment on his experiences with OTs, along with the premier builder of custom amplifier transformers on the planet, Sergio Hamernik of Mercury Magnetics. Sergio has been blueprinting exceptional vintage examples of the great transformers of the past and supplying discerning guitarists and their technicians with accurate reproductions that succeed in delivering authentic vintage tone. Stay tuned for reviews.

TQR: Good morning Mr. Bisbee. Your mission, should you choose to accept it….

Yikes, I expected the computer to go up in a puff a smoke!

So you want to know the inner secrets of output transformers, eh? Be forewarned – once you make that commitment, you’ll be cursing the days when you slept through “Advanced Frightening Mathematics 300….” How’s this for a wake up call? The following is the very first paragraph from Chapter V of the venerable RCA Radiotron Designer’s Handbook (4th ed.).

TRANSFORMERS & IRON CORE INDUCTORS

(i) Definitions

An ideal transformer is a transformer in which the winding reactances are infinite, and in which winding resistances, core loss, leakage inductances and winding capacitances are all zero. In such a transformer the voltage ratio between any two windings is equal to the turns ratio of the windings under all conditions of loading. Also, in such a transformer the currents in any two windings are inversely proportional to the ratio of turns in the windings under all load conditions….

The entire chapter is 53 pages long!

To keep things from getting out of hand, let’s just say that there are many factors influencing output transformer performance. Aside from an obvious fault like a shorted winding, fatigue of the core (the metal laminations) is the most prominent consideration in transformer output and tonality.

Fatigue is a natural consequence of normal operation. Suffice it to say that it’s a veritable Fourth of July inside the atomic workings of your output transformer every time you bust your best licks through it. The magnetic properties of the metal used in the core, the type of laminate used, the size of the core, and many other factors contribute to the final performance and longevity of the output tranny. Actually, most guitar amplifier transformers are made of rather inexpensive materials (yeah, try telling that to your parts supplier). The real high end stuff ends up in mega bucks hi-fi and industrial applications. In the grand scheme, guitar amps don’t rate the kind of respect we tone geeks assign to them.

To understand why a tranny gets fatigued, let’s remember what’s happening in the OT. You are transforming a high voltage/low current signal into a low voltage/high current signal. There are lots of electrons jumping around from point “A” to point “B.” This creates magnetic relationships and phenomena that act to age (or fatigue) the characteristics of the iron. Over time, the constant forces acting on the core change the ability of the laminate material to perform its duty efficiently. It will saturate quicker, and it reacts differently than when it was new, thereby altering the tone and performance of the amp.

To be sure, this is a slow, incremental change, and one which will take years of use to manifest as a perceivable degradation in tone. In fact, one of the reasons we like old ’50s amps is the quicker saturation and compression of an old, fatigued tranny, so don’t get too spun out of shape thinking your tone is being sucked away by a tired transformer. It may be your personal ticket to tonal nirvana. Just remember, however, that old amps with old trannys means old everything else, too… yin and yang.

Most of us are looking for the most reactive, intuitive amp that our minds and fingers can handle. In many cases, if the amp is checking out A-OK but it’s otherwise sounding a bit soft and saggy, perhaps a popping a new transformer in is just the ticket. Replacing an output transformer is not an inexpensive procedure, but it’s a simple one, and one that is easily switched back if the results are less than fruitful. As to the question of swapping out old components like caps and resistors that test and sound good, I advise leaving the old ones in when we are dealing with vintage pieces, the qualifier being that these components should test and sound good. Unless the ’57 Bassman amp in question is going to be used on an extended 300 date tour to sold out sheds, leave it alone. Most vintage amps will let you know that they’re giving it up by an audible degradation in tone and performance. Let’s face it, a 40-year-old capacitor will most likely fail in the next couple of decades (especially filter caps), so consideration must be given to the intended application of the amp. For most weekend warriors, the original passive components will suite you fine if they test and sound good. One last thought on the use of increasingly expensive NOS tubes in an amp that is old…. You will have to determine if you want to jeopardize a $259 pair Mullard EL34s in a vintage 40-year-old amplifier. When a coupling cap decides to fail, it can put the tube in a potentially dangerous operating point, causing it to fail too. I know I’m kinda swinging both ways here, but in this case, the vintage geek wins out (let’s not forget the tales of unscrupulous techs carving all the old Astrons out of vintage amps and then turning around and selling them for big bucks – it does happen, folks).

I could go into a more, more, extra more technical explanation of what’s happening in an OT, but I don’t want to lose everybody in a run down of big math with variables like reactance, gilberts, and flux densities that would scare everybody into suicidal seclusion….

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It was originally built around the design of one of Jim Marshall’s favorites, the Fender Bassman; like the Bassman, the JTM45 was actually a fantastic guitar amp. Because of its consistent popularity, Marshall has offered a reissue version of the head — more than 20 years after production of the original JTM45 ceased. While the reissue is built with modern components and assembly techniques, it retains much of the tone, responsiveness and character of the original, hand-wired versions of the early days. No wonder builders today still carry on the tradition of the JTM45, and guitarists continue to seek out the pure simplicity and touch response of this tone machine. To celebrate the JTM45, I got together with my Sunday afternoon amp group, after contacting a handful of respected amp builders who sent us their versions of the amp. We fired them all up alongside an original and a reissue JTM45 to take a listen — and to enjoy one of the best amps ever designed.

About the Authors

About 5 years ago, while playing a 9/11 benefit show, I had the good fortune to meet two people who would not only profoundly impact my life with tube amps, but would become lifelong friends. John Rossi and Tony Burns were there that day; Tony, a killer player and a regular on the Tempe/Phoenix music scene, and Johnny, his friend and amp tech, making sure Tony’s amps were running well in 115 degree heat at the outdoor amphitheater. When I saw Tony’s wall of Marshalls next to my backline of Marshalls, it was an instant conversation starter.

We spent time between sets that day discussing the various finer points of our amps and gawking at each other’s rigs. The show went great but my ’67 Super P.A. felt a bit stiff, and wasn’t reacting in the most flattering way. This incident proved to be the catalyst, as Johnny was an underground semi-retired tech and ultra-fanatic Marshall enthusiast, and he had some ideas that he wanted to try out. He invited me over the following Sunday to check out the amp, and to experiment with various preamp and power amp tubes while BBQ-ing and having a beer. Tony was there, and it became clear that we all had a deep respect for these amps; rather than modify them, we wanted to bring them back to their former glory. After five years, and dozens of hacked-up Marshalls coming back from the dead, here we are. Over that time we’ve learned more about these amazing amps than any of us ever anticipated, and we’ve have had a blast in the process. I have no doubt in my mind, based on my readings of the various amp forums, that there are plenty of groups just like us all over the world doing the same thing.

The Lineup

The lineup consisted of our own 1965 original and 1990 reissue heads, two MetroAmp JTM45s (a kit version as well as the GPM 45), a Germino Classic 45, a Wallace Amplification BKW45 and Mojave Ampworks’ new Special Edition Plexi 45 head. After searching through our collection of cabinets, we settled on both an eighties Marshall JCM800 4×12 with black back 25s, and a Mojave 2×12 cab with 1963-era Celestion Alnico Blues. It may sound strange that there were no pinstripe or basket weave cabs used for the roundup, but that wasn’t for lack of trying. Among all the members of the amp group, we actually have a pinstripe, a basket weave and a variety of Marshall 4x12s, but for some reason we always come back to the early-eighties JCM 800 cab with black back 25s.

That particular cab has more clarity, tone and authority than any other, and it remains our favorite in the bunch — despite the cool factor of the older cabs. The 2×12 with Blues was a natural choice, as that flavor shares similarities with the mid-sixties Marshall cabs and is also a popular speaker configuration for Bluesbreaker combos. The guitars we used were our standard array of Les Pauls from the ’70s, ’80s and 2000s, as well as a newer 2008 Fender Strat and two early-seventies Strats. With everything in the room (it was quite a sight!) we were ready to begin.

Original 1965 JTM45

To get our ears accustomed to the JTM45 sound, we began by firing up our ’65 head with a Les Paul. Normally, this head has EL34s in it, but we borrowed the Genelex KT66s from the Mojave and biased the amp to accommodate them. It made sense to us to use KT66s, because they were what the amp was designed for. With everything looking good, we flipped it from standby and beheld the beauty of this vintage masterpiece. It’s no wonder players and collectors are paying big bucks for these amps; everything we played through it sounded incredible.

What was amazing was how much of a rock ‘n roll amp this really is. Considering how long it’s been since it was conceived, the amp’s sound remains surprisingly current. The distortion is organic, full-bodied and earthy, and it allowed the personality of the guitar and player to shine through. While it was very easy to play, this is an amp that still requires a level of discipline and control to fully harness its capabilities. It makes sense that players who want to be heard would play on this style of amp, because like it or not, whatever you play through the amp is… well, amplified. It just comes out better.

We played through it for a good long time, switching guitars and speaker cabinets to hear it in as many different configurations as possible. Whether it was a Strat, a Les Paul, a 2×12 or a 4×12, the sound was always remarkable — perhaps the very definition of great tone. Subjective? Yes. Brilliant? Absolutely. Rolling back the volume on the guitars exposed a beautiful clean tone that was harmonically rich and defined, never muddy or dull. Even with the guitar’s volume knob all the way up, the dynamic response of the amp, and the way it musically fed back, was awe-inspiring.

Once we had established a base tone for comparison’s sake, it was time to play and listen to the other amps. Before I break down each individual amp and builder, I must observe that each and every one of the amps had ridiculously good tone, and they all sounded like JTM45s, but each had its own unique voice. Aside from the reissue Marshall, all of the amps are hand-wired. The reissue Marshall was of PCB-construction, and used the standard parts and components that Marshall was building their amps with during that era. I spoke with Mitch Colby from Korg USA (Marshall’s US distributor), who told me that the reissues have not undergone any significant changes since their reintroduction 20 years ago. While they are using the components that Marshall builds with today, they should yield very similar tones to the earlier reissue amps.

MetroAmp JTM 45 Kit and GPM 45 Custom Build

George Metropoulos is no stranger to the world of Marshall amps or to the online amp building community. Having run MetroAmp for some time now, George offers everything from fully built replicas of many classic Marshalls to ready-to-build kits and hard-to-find replacement parts for vintage Marshalls. A player, George honed his amp-tech skills by adopting a DIY approach, taking care of his own amp repairs on the road. This extended into repair work at home, and then really took off when amps began coming in for restoration rather than simple re-tubing. After his ’73 Super Lead was stolen from a gig, he realized it might be best to leave the valuable amps at home, and so he embarked on a never-ending quest to replicate the tone of the old Marshalls.

Like all the builders in the roundup, George is passionate about vintage Marshalls and obsessive over the details that make these amps so coveted. We received two amps from Metro: the JTM45 kit (which can be purchased already assembled for an additional $400) and the GPM45, George’s custom-built JTM45 using NOS vintage parts. When we fired up the MetroAmp 45s, it was clear that they both came from the same camp. Both amps were meticulously built and incredibly precise in their layouts. The main physical differences between the amps came down to the caps, resistors and tubes. Both amps shared the same iron and layout, so they also shared a lot of the inherent tone in their circuits. As George is a fan of the mid-sixties JTM45s, Metro’s transformers are based on the Drakes, rather than the earlier Radiospares iron [editor’s note: Kit also comes with optional Mercury Magnetics transformers]. Still, there was no question that the GPM45, which included NOS Phillips mustard caps, Allen Bradley carbon comp resistors and a gorgeous set of Genelex KT66s, was sweeter sounding.

While those differences accounted for a tonal upgrade, what made the differences even more compelling was the way they affected the touch factor of the amp. Much like our ‘65, the custom-built Metro had an ease about it that felt like a broken-in vintage head, making it a breeze to dig in, or to lay back on the strings and feel the amp act as an instrument. It was truly inspiring. Of all the amps in the roundup, this amp sounded most like our ’65 — frighteningly close! I should mention that the Metro kit version was actually plugged in first, and before comparing it to the GPM45, we all agreed we’d be thrilled to have one in our collection. We may be splitting hairs here to some degree, but knowing that anyone can buy a complete kit for under a grand, and have that kind of quality and tone — that says a lot.

Metro’s JTM 45 Kit:

Metro’s GTM 45 Custom Build:

Wallace Amplification BKW45

www.WallaceAmps.com

Brian Wallace has electronics in his DNA. His father, an electronics engineer, and his grandfather, an RCA tube repairman, were both instrumental in his early education and development in tubes and electronics. When he was young his father gave him a 75-in-1 electronic projects kit and further encouraged Brian by letting him watch as he built his own projects. Like all of the builders in the roundup, Brian is a player. He began modifying amps in 1974, when he removed the speakers and baffle in his Checkmate amp and replaced them with a baffle he created and some purchased speakers — altering the sound of the amp and thus beginning his lifelong journey. In 1995, he was approached by Guytron Amplification to help out while they were getting started. A positive experience, it propelled him to the next level and led to the creation of Wallace Amplification, which now offers several amp models as well as replacement transformers under the Marstran name.

Wallace’s first amp is the BKW45, but he is more than a clone maker. Recently he introduced the Abaddon, which is a 50-watt master volume head consisting of four gain stages in the preamp. There is much more to come, including a line of pedals and a reissue of the Fuzz Ace pedal he made back in the early ’90s. The BKW45 is a unique flavor of JTM45. A hair darker in tone and possessing slightly less gain than all of the other models, including both the vintage and reissue Marshall, it yielded enormous bloom and a bold, thick, sustaining quality. Even though there was a little less gain, it didn’t affect playability, and we never struggled with the amp. It was one of the rarest qualities I’ve experienced in an amp, and certainly an unexpected bonus.

The Wallace had a magical ability to push notes through loud and clear while still being able to dish out gritty and harmonically pleasing chords that didn’t fight the non-perfect intervals they were built on. This all came out of an amp that was using tubes you can buy today without breaking the bank.

Speaking of breaking, check out the sidebar on what the BKW45 was subjected to by UPS en route to our roundup. In spite of the gorilla treatment it received, the amp arrived without shattered glass and performed flawlessly throughout the entire set of three sessions of playing and listening. That’s a testament to a solidly built and roadworthy piece of equipment. And one look inside the amp will show what a dedicated and precise builder Wallace is. In tone and build quality, the amp is a work of art.

Ever wonder what could happen to your amp in shipping? In the case of Brian Wallace’s BKW45 amp, UPS had a field day, and decided it would be a lot of fun to throw it around. When the amp arrived, it was packed neatly in a new cardboard box with padding inside suspending the padded road case that housed the amp. That’s double-boxed and protected by a case built for heavy abuse. Sadly, it took one good slide down the end of a ramp and collided with either another box or the wall of the truck. Though the box didn’t show any signs of abuse on the outside, it was clear that something had shifted when I opened the case. Take a look at this picture of the damage and the way the entire amp was shifted to one side because of the impact. Believe it or not, the tubes didn’t shatter and the amp worked fine, but it was cosmetically damaged by a broken front Plexi panel. This isn’t the first time this has happened, but it’s the first time I’ve seen it happen with this type of road-worthy packing. Let this serve as a reminder to always insure your amps, as the shipping company can’t tell if you’ve got a bag of peanuts in a box or an amp that was lovingly built by somebody like Brian.

Germino Amplification Classic 45

www.GerminoAmps.com

Greg Germino is another lifelong guitarist who was bitten by the tube-amp bug after catching the Allman Brothers Band back in 1972. He was so inspired by that show that he switched over from acoustic to electric guitar and began taking electronics classes in high school. In 1979, he requested schematics from both Ampeg and Unicord (Marshall’s US distributor at the time) and began his hands-on education with tube amps. He spent the ’80s at an electronics job, and by the early ’90s he was moonlighting doing tube amp repair for a few music stores. He continued to play live with both 50W and 100W Marshalls during that time and moved to Durham, NC to work at Bull City Sound — working on tube amps from the big-name amp companies.

This led to Greg’s being commissioned by Mojo Musical, where he built their Tone Machine amplifier. The following year, 2002, he began work on the prototype of his Lead 55 amp, which debuted in May of 2002. The Classic 45 model is based on the earlier Radiospares-style output transformer, rather than the Drake 1202-103used in the ’65-’66 era, and the circuit is exactly what you would find in an earlier original. The Radiospares-style OT is supplied by none other than Chris Merren, who is highly regarded in the world of Marshalls, and known to make some of the most accurate transformer replicas out there.

The Classic 45 was the only amp in the roundup that used 6L6 power tubes. Greg’s decision to use them was a combination of staying true to the earliest tubes Marshall used on the original JTM45 amps and his belief that the current crop of 6L6s sound and perform better than newer KT66s. NOS and vintage 6L6s are also less expensive and more plentiful than NOS KT66s. Our immediate response to the Classic 45 was that it was a lively and aggressive amp, with tons of power that made the pick explode off the strings. In ways it reminded us of our favorite ’67 Super Bass in its volume and attack, but it still retained the sound of a 45. It may very well have been the loudest amp of the bunch, and that volume translated to a feeling of excitement that made the amp extremely fun to play. It was present without being shrill and had a super-tight bottom end, no matter what guitar we played through it. While the Classic 45 had tons of natural gain on tap, it also cleaned up nicely when rolling back the volume on the guitar, revealing a bright and sparkly chime. This amp is a real beast, and it could hold its own against 100W amps without flinching.

Mojave Ampworks Special Edition Plexi 45

www.MojaveAmpworks.com

Anyone familiar with the JTM45 would surely be jealous of Victor Mason. Not only has he seen more than his fair share of vintage Marshall, Vox, Hiwatt and other rare treasures come through his shop, but Victor recently acquired 26 of the all-time greatest JTM45s ever assembled via the Kronemyer collection, and he’s got the pictures to prove it! This is just one of the factors contributing to the obsessive nature of Mojave (and the associated Plexi Palace). Having been around for over a decade on the internet, Vic has been repairing, restoring, buying and selling vintage Marshalls for quite some time now. Stemming from his early desire to find out how EVH created the classic brown sound, Victor embarked on his journey through countless hours of digging into vintage amps and learning where their strengths and weaknesses lay. Mojave now offers an entire line of amps to serve the classic Marshall tones and well beyond with innovative features and designs. The Mojave Plexi 45 also has two very unique features over a stock JTM45. First is a simple feature to allow volume control by way of throttling the power level. Second is a line level output, which is adjustable and incorporates a ground lift.

Standing apart cosmetically from the rest of the amps, the Special Edition Plexi 45 is built on the same footprint as the Coyote and Scorpion designs, with a white-and-black color scheme and chrome hardware. The head is built with an open grille cage that allows for maximum airflow to keep the set of completely NOS glass cool. The 45 supplied for the roundup consisted of a pair of 1970 NOS Genelex KT66s, 3 Mullard 12AX7s and a Mullard GZ34. Like the Germino, the Plexi 45 is based on the Radiospares transformers, which are custom wound by Mercury Magnetics.

The chassis is a thing of beauty; the .09″ thick aluminum, with a high tensile strength and welded edges and seams will ensure it will not flex, bend or develop fatigue, like the early, folded, softer chassis, and will prevent the heavy transformers from causing the chassis to sink in and sag. Mojave deviates from the original JTM45 by using modern, tight-tolerance parts. Custom manufactured caps and metal film resistors allow each amp to sound as close to the one built before it as the one after it. Consistency is something that Vic definitely strives for, and it shows in the build quality and attention to detail, and the desire to add convenient functionality to his amps.

We found in testing that not only did the amp have an extremely low noise floor, but that it was an authoritative and powerfully voiced amp. There was definitely something different in the tone of the Plexi 45; it was cleaner sounding, but still very bold. Having been to Vic’s shop, I was fortunate enough to play one of the 26 JTM45s he had acquired, and I’m positive that the experience with those amps had more than a little to do with the design of the custom Mercury Magnetics’ Radiospares transformers made for his Special Edition model. The amp is built like a tank.

Marshall Reissue JTM45

www.MarshallAmps.com

While the reissue looked very similar to the ‘65 on the outside, especially due to the fact that it’s already 20 years old, the differences on the inside were quite pronounced. Assembled with more modern methods, and using a PCB rather than hand-wired turrets, you could easily be fooled into thinking that it wouldn’t perform like the others. This particular amp was the only one in the bunch to use EL34s rather than KT66s or 6L6s, so the sound was definitely different. It was incredibly loud and focused sounding, and actually had many of the characteristics of a Super Lead. The sustain and power of the amp was incredible, and for an amp that can be found used for around $1000, this is a sleeper bargain. Marshall has taken some flak for their amps sounding stiff and cold from the factory, but with a little attention — slightly hotter bias and good tubes — this amp is a monster. And just because it says it’s a 45-watt amp, don’t harbor any illusions that it would be a good bedroom amp. This is a loud and powerful beast, and a tone machine as well.

The Blindfold Test

As a final, fun test, we did a blind study, to see how accurately I could identify each of the various amps in the roundup. Johnny and Tony set up the group of amps, and I sat in a chair with my back turned away from them. With the guitar plugged in, they began to fire up the various amps, and we got rolling. Out of all the amps, I was always able to distinguish the Wallace BKW45, due to it’s slightly darker sound. The Metros were also fairly easy to spot, but I ended up guessing the kit as the custom build and vice-versa. The ‘65 was also an easy amp to recognize, but as ear-fatigue set in, the lines began to blur substantially. Pretty soon, I was confusing the Germino for the reissue JTM, the Mojave Plexi for the Wallace, and the Metros for the real JTM. It just goes to show you that all of the amps performed remarkably well, and you can be fooled when you’re not seeing what you’re playing, so never discount a PCB reissue head as a second fiddle to the real thing. In the mix of a band, these differences become small, and any one of these amps would hold their own any day of the week.

Wrapup

To have the opportunity to play through so many variations on a classic theme was not only fun, it was educational. Each one of the builders excels in creating their own unique version of the great rock and roll amp that Ken Bran, Dudley Craven and Jim Marshall built back in 1962. While like all Marshalls, the JTM45 went through changes in tubes, components and designs over its lifetime, there is a trademark flavor and color that still can be found in all of them. Not everyone can afford a vintage 45, but with the help of these builders we have the opportunity to get into that sound and have build quality that will last for years.

Source: https://mercurymagnetics.com/pages/news/PremierGuitar/PremierG-20.htm

Simple Amps’ Big Iron 6VA amp is simple, old school and responsive to your guitar’s controls.

When I received the Simple Amp for review I could hardly ignore its dimensions; it’s a pretty impressive looking package, to be sure. The cabinet weighs about 60 lbs, and the head about 30. The model I received was the Big Iron 6VA, in a head and 2×12 cabinet configuration, sporting the striking Black Widow look.

The 6VA name refers to the output tube configuration, which is two 6V6GT tubes (Tung Sol). Other models using 6L6 and EL34 are available as well; standard preamp tubes are Mullard 12AX7s. The amp also features two 5AR4 rectifier tubes, and the manufacturer states that an optional 12AU7 will give a more pristine clean tone if desired.

So Simple

The head is a thing of both beauty and simplicity. Only two knobs — Volume and Tone — are presented on the front panel. The rear panel features two output jacks, an impedance selector, AC voltage selector, and the AC input module. One cool feature here is that it carries one spare fuse inside the fuse holder for easy access, in case of an emergency. Construction is impeccable, with hand-wired turret boards, and Mercury Magnetics power transformer, output transformer and choke. The 6V6 model scopes out at about 30 Watts.

The speaker cabinet is equipped with two Celestion Alnico Gold G12 50-watt speakers, set up vertically and wired for 8 ohms. It features an open-back design and has aluminum speaker baffle and bracing. Although I didn’t have an opportunity to hear the cabinet with a wooden baffle, I’d have to say my impression was that the aluminum baffles and bracing made it a bit brighter, and certainly tighter on the low end, than most open-back cabinets I’ve played. This example was mono wired, but a stereo option is also available. The cabinet was solidly constructed of 11-ply and 13-ply Baltic birch, and sounded very tight when pushed.

Another cool thing is that the manufacturer includes both a speaker cable and an instrument cable by Solid Cables, which transfer some of the cleanest tone and response around. They want to make sure that this amp is run under optimum conditions, and it shows their dedication to getting the perfect tone out of the amp.

So What About the Sound?

The creator of this amp, Joel Jones, tells me that his idea for this design comes from the desire to turn the amp up to ten and control the whole clean/dirty sound from your guitar’s volume. Doing it this way allows for the all-important power tube saturation. It’s easy to overdrive a bunch of 12AX7 stages for distortion or overdrive, but when the power section comes into play, the whole dynamic changes. The amp can be very warm and clean at lower settings of the Volume control, especially using the bottom input, which has less gain, but touch sensitivity is also affected. The lower input might be better for some players who derive their tones from pedals, as the higher headroom would let their reverb and delay effects work better. Happily for many players, this amp has more available gain on ten than most amps of this type. The low end is smooth and tight. Some single-volume/single-tone amps sound pretty bloated when cranked in this fashion, but not this one.

The Simple Amp 6VA is also very pedal friendly. I used a Tube Screamer pedal and an old Marshall Guv’nor pedal and got amazing distortion and overdrive sounds with both a Strat and a Les Paul. The Fender Stratocaster used was a typical American Vintage 57 reissue with a maple neck and Duncan pickups. The Les Paul was a 1969 Black Custom retrofitted with original 1959 PAF pickups.

The type of tones I was able to achieve varied according to the various pedals I used. The TS808 gave me a very good rendition of SRV and Robin Trower when used with the Strat. Through this pedal with the Les Paul, the classic British rock tones — Bad Company and Zeppelin — were readily available. When I switched to the higher gain Marshall Guv’nor pedal and the Strat, I found that David Gilmour tones and even a bit of Yngwie on the neck pickup were no problem. With the Les Paul and the Guv’nor I found Gary Moore and Neil Schon type of sounds (I should mention here the volume was set at about 9, and the tone about 7).

I have to say that for heavier rock tones, you will need to use a pedal. The Strat-blues SRV thing is really no problem with this amp paired with any type of Tube Screamer. I was surprised at the volume the amp produces. This is probably the result of the two 12” speakers stacked vertically, as well as the cabinet design. The guitars cleaned up to pristine clean when their volumes were reduced, making it a very usable unit for those comfortable with controlling it this way. The Simple amp has a wonderful warm tone and texture to its sound, which is fairly hard to come by these days. I noticed exceptional touch sensitivity to the amp, and it responded well to different types of picking techniques.

The tone control on the amp was very wide ranging, going from very dark to some pretty screaming highs. On the high end the amp seems to have more gain, but even with the amp cranked and the Tone knob turned all the way treble side, the top end was not harsh. It was very easy to dial this control in to just the right amount of brightness. The dual rectifier tubes in this amp should not be confused with the similar specs of other brands. In this application they are there to provide just the right amount of sag to the power supply. I think this is probably the reason for the exceptional touch sensitivity of the amp.

The Final Mojo

I found the Simple Amps model 6VA to be an excellent amp for players who are comfortable with controlling their tones from their guitar. It may not be the best choice for players who are used to the staggering gain and sustain of Boogies and Bogners and the like. This amp is not in my opinion, a competitor to those types of amps. It does, however, produce tones that would be difficult to get from the modern high-gain amp. Old school players will love it. It is well built, and even though it is larger than most amps of its type, it is worth the effort to transport.

Buy if…
you’re looking for a great, simple amp with clean/dirty sounds you can control from your guitar’s volume.
Skip if…
you’re looking for a lightweight amp, or prefer the massive overdrive of a modern high-gain amp.
Rating…
Street $2650 (head) $1150 (cabinet, as tested)

Source: https://mercurymagnetics.com/pages/news/PremierGuitar/PremierG-19.htm

Mercury’s NEW MultiChoke offers you these important benefits:

• The first tunable chokes to help you fine-tune your amps!
• Quickly helps you find your amp circuit’s sweet-spot!
• Versatility without having to do serious amp mods!
• A BIG TONE bang for not a lot of bucks!

Think of a choke as a shock-absorber for your amp’s power transformer. Did you know that upgrading your tired old or wimpy reissue stock choke — or adding a Mercury choke to an amplifier that doesn’t have one* — will actually extend the life of your power transformer and rectifier?

*Amp manufacturers often cut costs by the use of a resistor in place of a choke. This choice has absolutely nothing to do with tone, it’s purely economic. Replacing that resistor with a choke is a low-cost upgrade that’ll usually give you a huge improvement in tone.

Your amp’s tone noticeably improves with any peaked and tweaked, hand-tuned choke from Mercury. Mercury users tell us that they hear a tonal richness that was not there before adding one of our chokes. Why? Because a choke provides musical smoothing to your amp’s circuit. It also has a huge impact on touch-sensitivity and tone dynamics.

A choke is so much more than a simple inductor. It can also store energy like a capacitor. Better voltage regulation results from using premium-quality chokes. The choke puts less stress on your power transformer and permits higher load currents to be drawn from vacuum tube rectifiers without exceeding their peak current rating. This means life extension for your tube rectifier — and even solid-state rectifiers run happier!

Mercury’s NEW MultiChoke is in a league by itself. The MultiChoke allows you to quickly and easily audition several different choke values to determine the best possible fine-tube the tone from your amp. And, the MultiChoke saves time and money by eliminating the need to purchase a stack of single-value chokes — not to mention all of the added time needed to solder/de-solder leads for your tests.

Depending upon your needs, Mercury offers several MultiChokes with varying value sets. Currently available sets include:

• 1, 2, 3, 4 & 5 Henrys
• 1, 3, 5, 7 & 9 Henrys
• 2, 5, 7, 10 & 12 Henrys
• 5, 10, 15, 20 & 25 Henrys
• 10, 15, 20, 25 & 30 Henrys

Mercury’s MultiChoke come in 3 sizes* with these center-hole-to-center-hole mounting dimensions:

• “Micro” = 2 inches
• “Mini” = 2-13/16 inches
• “Large” = 3-9/16 inches

*Check our catalog for size availability.

For a little dough, and some help from Mercury, you will be on your way to having a better sounding amp.

Also see our adaptation of the MultiChoke to the Orange “Tiny Terror” Upgrade Kit.

Shop for Amp Chokes

It’s no secret to any of us that Fender’s Deluxe Reverb has long been considered the guitar player’s ultimate desert island amp. It’s lightweight, compact, incredibly sturdy and dependable, and it captures the essence of classic ’60s Fender tone. Blackface models built between 1964 and 1967 can cost as much today as a clean vintage Super Reverb, and Silverface Deluxe reverb amps built from 1968 through the mid ’70s remain a bargain, selling for $600-$900. There is very little difference between unmodified amps built during the two eras, except for a couple of caps connecting the output tube grids to ground in the Silverface amps, and a variety of stock speakers, including Jensen, CTS and Oxford. There is absolutely no reason why a Silverface Deluxe Reverb can’t sound every bit as wonderful as any Blackface amp, and some of the Silverface amps will sound better than some Blackface Deluxe’s you’ll find. Local amp wizard and advisory board member Jeff Bakos has observed that some of the exceptional Deluxe Reverb amps he’s heard (and he’s heard hundreds of Deluxes) seem to have “hotter” power transformers, and the slight inconsistencies in the way some transformers were wound can make a big difference in tone. Earlier today we heard as much in Jeff’s shop in a ’66. Unfortunately, it all comes down to the luck of the draw when finding those special amps. If there is fault to be found with the sound of a Deluxe Reverb (and it really isn’t a fault), it’s the speed at which the amps begin to break up. The clean threshold of the Deluxe is pretty low, and while this characteristic feature is an irresistible attribute to many players, we wondered what could be done to make the Deluxe Reverb even more versatile without losing its unmistakable tone. The modifications we describe here are very simple as modifications go, and all of them are easily reversible. We encourage you to try some and let us know how you like the results.

We started with a beautifully preserved ’68 Deluxe Reverb acquired on eBay for $900.00. The owner had replaced the original particleboard baffle board with pine, recovered it in vintage Blackface-era grill cloth, and installed a repro Blackface plate. We also received the original baffle board covered with the original blue and silver grill cloth, the aluminum trim, and the Silver face plate. We had acquired a replacement output transformer from Mercury Magnetics, and although the original transformer seemed to be working fine, we wanted to see what we might hear by swapping transformers. The Mercury ToneClone series transformers is the result of years of testing in which Mercury blueprinted some of the best sounding output transformers that could be found in vintage amps and painstakingly reproduced them in every detail. At first, the new transformer didn’t sound starkly different from the original – it sounded exactly like the original. But over time, it became increasingly apparent that the amp was behaving with more dynamic response. Notes and chords were imaging differently than before. Individual notes within chords were better defined, the amp responded faster to touch, and harmonics were more pronounced and complex. We’re the first to subscribe to the “don’t fix it if it ain’t broke” school of amp maintenance, but in this instance, the fix was a good one.

One of the easiest things you can do to Deluxe Reverb amps is rebias them for 6L6 power tubes. The outcome is predictable and sublime — more power, more headroom and better lows that won’t fall apart. Call it the “Beano”” treatment for your farting Deluxe. Jeff Bakos rebiased the amp after we had installed a pair of RCA black plate 6L6s, and we were mighty pleased with the results. You lose some of the compression and darker character of the 6V6 tube when you switch to 6L6s, but there is very little downside to the trade off — just big, bloomy 6L6 tone, and lots of it.

After installing the RCA 6L6s, we opted for an NOS RCA 5751 rather than the 12AX7 in V2, and it really smoothed out the tone to silky perfection. We also experimented with a Chinese 5AR4 rectifier tube, a new Sovtek 5AR4 and a Mullard 5V4. The Mullard pulled the volume back down ever so slightly, but it also seemed to sweeten the tone, rendering a throaty voice that fell nicely in between the “old”” amp with the 6V6s and the “new” one with the 6L6s. Either tube is a good choice — you’ll just have to decide which sound you prefer. Among the 5AR4s, we actually preferred the sound of the Chinese tube over the Sovtek, although the Chinese 5AR4s aren’t quite as robust. Our Deluxe came with an absolutely dreadful (recone?) non-original Fender “blue label” Oxford ceramic magnet speaker that was commonly used in the Bassman, Twin and Pro Reverb. We replaced it with n Eminence Legend V12, and this speaker turned out to be a “best buy.” The V12 features a British cone, and the tone is extremely round, well-balanced, and warmer than the Jensen C12N. It’s rated at 80W, and as usual with Eminence products, value and tone are absolutely unmatched for a speaker that sells for under $50.00. Jeff also likes the Legend 125, which is rated at 50W and built with a 1.5 inch voice coil and a slightly lighter magnet. As we observed in Eminence founder Bob Gault’s interview, the low price of an Eminence speaker is no indication of cheap construction or tone. The speakers rock, and they are voiced to appeal to a wide variety of players. We continued experimenting, and our next choice was a new Jensen C12K. We had seen this speaker in Victoria and Fender Twins, and it’s a massive thing. Built in Italy, and rated at 100W with a 2 inch voice coil and 50 oz. magnet. The C12K in a Deluxe with 6L6s yielded huge clean tone from top to bottom, with more high frequency emphasis than the Eminence speakers, and no speaker distortion whatsoever. The Jensen C12K in a Deluxe won’t be everybody’s idea of the perfect match, but it you crave a wide-open, big sound with nothing but clean speaker, the Jensen is a worthy contender at $90 retail. The last speaker we installed was a paper (not hemp) Tone Tubby from A Brown Soun. The paper-cone Tone Tubby is voiced a little brighter than the hemp cones, and we were floored by its rich, smooth character and charm. Jeff described it as being “silky smooth,” and just what he expected, with great lows, stout midrange, and creamy, creamy highs. Now, do you really need a $200 speaker to sound great? Of course not, and the price of a Tone Tubby is not for everyone. But if it’s the speaker for you, you won’t rest until you get one, and nothing we’ve heard can touch it. Enjoy yours, Eric, and enjoy milking some more of the good thang out of your Deluxe, gang. Hey… if not now, when?

The Epiphone Valve Junior is a small 5W amp head that is first most noteworthy because it is… well, cheap. Especially considering it is a tube amplifier, selling for $129 is frankly a bargain. Because of its simplicity and price, it has had a bit of an underground following being a pure-tube circuit with a single 12AX7 in the preamp stage and an EL84 as its output tube running Class A. The amp has 4, 8, and 16 ohm output jacks to enable a wide use of cabinets.

All in all, with this setup and a single volume control, players can get an idea of how tube distortion and compression changes as the volume is turned up. And it can all be done without the need to put in ear plugs that you would otherwise need when trying similar activity with a 100 watt head.

And the amp on its own sounds o.k. It’s obviously not wildly versatile, but “old school” style players can set an amp like this to obtain as much gain they’d like, then they can clean up their signal by use of their guitar’s volume control. Problem solved. Not enough volume for gigs? Throw a microphone in front of the cabinet.

The Mercury Magnetics Modification

The basics are changing the power and output transformers and adding a choke. There are some additional filtering and component changes. While the amp stock has one EL84 tube, the mod kit adds an additional 6V6 tube that gets blended to increase power.

The documentation that comes with the kit is excellent and really makes performing the mod easy. Our resident amp builder Mike Mullen took the amp further and created a new handwired board for the Valve Junior Kit — just for fun. He also flipped the chassis so that the front of the amp has the mesh screen and makes the amp look a bit more like some of the contemporary designs (you can see this look in the videos).

As one would expect with the change in transformers and the 2nd power tube, the amp is louder. In fact, it’s now loud enough to play with a full band of drums, bass, guitar and singer — unless you have a hard-hitting drummer that is! What you can expect is an overdriven sound great for rock and blues. But if you need clean headroom, you’ll still want to mic it up. The modified amp is very dynamic, with much more clarity and fullness on the lows when the amp is turned up to bring on the 6V6/EL84 combination of tube compression.

Where the modified Valve Junior may now have its strongest application use is for recording. It’s no secret that some of the greatest recorded sounds in rock and roll and blues history were done on smaller amps.

The modification kit sells for $299 through www.MercuryMagnetics.com and those with basic soldering skills can do the job with the step-by-step documentation and CD being a big help. While some may balk at the fact that they now have spent a total of about $400 for the amp, transformers are indeed the heart of the amp’s circuit, especially the output transformer. The output transformer is the final link between the tubes and the speakers, and we know from past tests what a great output transformer can do to improve the tone and fidelity of a tube amp. With the Upgrade Kit complete here, you’ve now got a custom boutique amp for about $400 — which would still be considered a bargain for many.

We recorded a couple of basic videos to show some of what the Mercury Magnetics modded Epiphone Valve Junior can do when plugged straight in just playing some basic blues and rock style lead and rhythm (no Charvel shred-style this time folks).

The first demo uses a Les Paul, the second a Stratocaster.

Source: https://mercurymagnetics.com/pages/catalog/kits/valvejr/LegendaryTones/LT-01.htm

Fender designed and built more than one transitional, non reverb blackface combo amp that would soon acquire reverb and a new name, including relatively small numbers of blackface Princetons, 4×10 Concerts, 1×12 Vibrolux and 1×15 Pros. We acquired a 1×15 blackface Pro, and while it ultimately proved to be an extraordinary exceptional amp, we were also reminded of the potential pitfalls that exist when buying old amps sight-unseen, as well as the potential rewards.

We found the ’64 Pro listed on eBay and bout it from a dealer after requesting a detailed photo of the chassis and circuit. Proudly described as “the best amp in the store, “the rare ’64 blackface Pro is essentially a blackface Vibroverb without the “verb.” Do we have your attention yet? Three caps had been replaced, the original baffleboard had been professionally converted to plywood with the original grill cloth remaining intact, and an on/off pot had been installed for the tremolo intensity control that bypassed the tremolo circuit when rolled to “1” with a click, adding gain that would otherwise be missing in the Vibrato channel. We pulled the JJ power tubes and assorted Russian pre-amp tubes and replaced them with lightly used,“test new” RCAs from our stash, rebiased the amp and fired up the Pro….

Sounded like shit. We had been here before with a dead-mint ’64 Vibroverb bought years ago that had passed through a certain amp guru’s hands in Pflugerville, Texas.How could a vintage Fender sound so bad we wondered? Turned out that the value of the bright cap on the Vibrato channel had been changed on the Vibroverb, rendering a thin, scalding tone that would have given Ed Jahns fits, as it did us. Changing the bright cap back to spec immediately restored the Vibroverb to its rightful pace in history, but the Pro had other problems….

The baffleboard swap and added switch on the tremolo intensity control were clues that someone had also spent time troubleshooting the amp, probably trying to detect the cause of the Pro’s weak output, thin tone and curiously harsh edgy distortion. The amp just didn’t sound right. We pulled the original, reconed Jensen C15N dating to 1964 and subbed in an Eminence Legend, but the Pro still sounded choked-off, linear and wrong, so it was off to Jeff at Bakos Amp works on the Friday afternoon before Memorial Day weekend in a frog-chokin’ Georgia thunderstorm. When the going gets weird, the weird turn pro…..Now, this is the difference between someone who really knows his craft and a hack….Jeff plugged his bench guitar into the Pro, hit a couple of chords, issued a single grunt of displeasure and caustically observed, “Something is definitely fucked up.” With the chassis on the bench, Jeff scowled at the choppy sine wave the amp produced on his scope as he checked voltages with his multimeter. “I think the output transformer is going down slow—it measures 11 volts and it should be reading 16….” He clipped in a substitute OT from a stout old Fisher hi-fi, plugged in and hit a chord… “That’s closer to what it’s supposed to sound lie….” And sure enough, the missing lows and mids were present, the raspy treble tones were subdued, and for the moment, the Pro showed promise. We called Paul at Mercury Magnetics and ordered a black-face Pro Tone Clone replacement trans-former, shut it down and wished each other a good holiday. A week later the Mercury Magnetics replacement output transformer had arrived. Jeff wired it up, and then turned his attention o three silver mica caps that had replaced the original ceramic caps in the phase inverter and tone circuits. Jeff: “Somebody probably read an article about how these would bring the high end up, but I prefer the ceramics—always have. Besides the effect of the voltage from the old output transformer being low, these silver mica caps were contributing to that brittle tone we were hearing. They are the wrong value, and they changed the entire sound of the amp.” Jeff pulled all three silver mica caps and replaced them with the correct ceramic disc caps, and since an on/off switch had already been installed for the tremolo, we mounted the 25K mid range pot in the back panel hole for the extension speaker jack. With the Pro now thoroughly put right and the midrange pot added, Jeff hit a few chords, moved the EQ and volume settings around a bit in both channels, smiled and said, “That sounds really good. Yeah, that’s it.”

Back in our music room, the final step was to re-bias the Proat 34mA with an AmperexGZ34 rectifier and our last pair of vintage RCA black plate 6L6s, which in unused, new old stock condition have soared to $400/pair. The re-labeled Tube NOS Phillips JAN 6L6 WGBs we had tried sounded good—but the smooth warmth, exceptional musicality and deep harmonic content of the RCAs just can’t be beat, and it is a difference you can definitely hear. Smoke ’em if you got ’em….

We lit up the Pro with the ’63Fender Reverb unit and reverently smiled at the jaw-dropping tones pouring from the big Eminence Legend 15. Imagine the sound of a slightly kinder, warmer sounding 40 watt Super Reverb void of the sharp, penetrating treble presence that has sooften left our ears ringing for hours after a tumble with a blackface Super. The sound of the ’64 Pro is all Fender, with solid bass that doesn’t fall apart at high volume as the smaller blackface combos can,sweet, singing treble tones, and now… a mid range control that can gradually push the amp beyond its original, clear and liquid “scooped” mid range voice to an exceptionally thick, “mid-Atlantic” roar that unleashes heavy sustain and rich, musical distortion as only a Fender can. The Pro brilliantly complements every guitar we own, producing the essence of classic Stratocaster, Tele, P90 and humbucker tones with clarity, depth and lush fidelity that literally fills the room. Yes, there are different and equally worthy tones to be had from the British classics,but we have never heard a more beautiful sounding or versatile Fender amp—one that can range from crystalline, blackface clarity to the full burn of an early blonde Fender Bassman at much friendlier volume levels. The Pro can get plenty loud, but it’s a loud that doesn’t kill you in the style of a Showman, Twin or a Super Reverb.

The irony in this unexpected discovery has not escaped us,and perhaps the weight of it is now becoming clear to you, too. This project did not begin well, and we confess to experiencing some remorse when the Pro arrived with a few bad mods, weak and thin from the original output transformer going down, and generally just sounding very wrong. Our dismay was soon displaced by genuine enthusiasm; however, as we were reminded that this is indeed what the quest for tone is all about it. We’ve acquired absolutely bone stock amps in perfect working condition that just couldn’t tote the note, so why should we expect to buy a 44 year old amp that’s been played without it needing a little repair and restoration work? The end entirely justifies the means.

Having finally experienced the Pro’s singular, exceptional sound, we wondered what had caused it to be relegated to such obscurity among all the Fender black face amps. Like the Vibrasonic and Vibroverb, perhaps it was doomed by the presence of the single 15” speaker. Like the Pro, the blackface Vibroverb 1×15 was produced for less than a year, and with the introduction of the 2x12Pro Reverb in 1965, Fender would no longer produce a 1×15 combo until the introduction of the silver face Vibrosonic in 1972. Yet, the earlier 1×16 Pros had been Fender’s flagship amps during much of the tweed era, and in 1960 the 1×15 brown Pro ranked second only to the1x16 Vibrasonic in the Fender catalog. Somewhere along the way, the 1×15 combo had clearly fallen out of favor with Fender, guitarists, or both, and given the short life span of the Vibroverb, even the addition of reverb couldn’t save it.

Twenty years later, Stevie Ray Vaughan elevated the Vibroverb to hall of fame status, otherwise, the 1×15 com-bos seem to have been perceived as “uncool” for anything bug jazz and blues, as if wearing a jacket and tie were required to play them. The Pro is a great blues amp, but it’s also a great rocker, and equally well-suited for jazz, pop and country. With far more clean head room and power than any tweed Pro and much stronger distortion, sustain and dynamic character than a brown Pro, the blackface Pro reflects Fender’s ongoing pursuit of more powerful, cleaner sounding amps, but unlike the black face Bandmaster, Tremolux and Showman, and Pro can really rock the house cranked. We suspect it’s a single 15 and missing ’verb that throws people off today, yet in’64 Pro shares its DNA with the ’64 Bassman and all the highly prized blackface combo amps, including the Deluxe Reverb, Vibrolux Reverb, Super Reverb and the heavily prized and hyped Vibroverb.

The contrast between the Vibroverb’s Holy Grail status versus the lowly blackface Pro simply underscores how easily we can be blown off course by what isn’t hyped on the Internet or in print, and by the powerful logic that suggests if anything 44 years old is truly noteworthy, “we” would already know about it. Well, apparently “they” don’t. But you do. Blackface Pros can be found for $1 500–$2,000,with originality and overall condition driving prices accordingly. Like the Deluxe, we wouldn’t buy one that has had all the blue molded capacitors or Allen-Bradley resistors replaced, but the transformers available today from Mercury will sound every bit as good or better than the originals, and as we have said so many times in the past,the Eminence Legend 15 is spectacular. Add some good,current production or NOS tubes and you will have been delivered to a place well beyond the common man’s limp and shriveled imagination. Now Quest forth….

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Chatsworth, CA (May 19, 2010) — If your amp was submerged or has sustained any water damage in the Nashville Flood, call Mercury Magnetics. Mercury is offering a free amp transformer service for all flood victim amps.

Here’s how it works: Mercury has designed a technology specifically to salvage and restore flood-damaged transformers. The process includes inspection and testing, a custom process of evacuating the moisture, and re-varnishing of any transformer without charge. They’re only asking that you pay the shipping each way.

“This is a vitally important service we’re offering. And we hope that everyone takes advantage of it,” said Patrick Selfridge, Mercury’s Service & Support Network Manager. “Especially for the vintage and rare amps that otherwise are never going to sound the same if this process isn’t done correctly. There’s a potential tragedy of some historically important tone being lost forever if their transformers are not properly brought back to life. We’re proud to say that so far our engineers have a 90% success rate.”

Mercury advises owners not attempt to power up the amp without having the transformers serviced. To do so will almost certainly “fry” them. However, if a transformer was damaged beyond repair, Mercury will offer the choice of a rewind, replacement or upgrade at substantial discounts.

Contact Mercury for any questions or concerns you may have and for special shipping instructions.

For more information:
Mercury Magnetics

Source: https://www.premierguitar.com/articles/Mercury_Magnetics_Offers_Free_Amp_Transformer_Service_For_Nashville_Flood_Victim_Amps

Shop for Guitar Amp Transformers

THERE’S AN INHERENT dichotomy when it comes to guitar amplifiers; the more TLC that goes into their construction, the tougher they are. Think about your average mass produced amp… then consider Sommatone Roaring 40. Built with heaping helpings of TLC by James Somma and Dan Arango, the Roaring 40 employs a heavy gauge welded aluminum chassis, Mercury Magnetics transformers, stainless stell hardware, electrolytic capacitors by Sprague and F&T, silver-plated Teflon wire, four JJ EL84 power tubes with O-rings and heavy duty retainers, four JJ 12AX7 prevamp tubes (and one more in the rectifier), tubular polypropylene signal capacitors, a U.S.-made Eminence Red Coat 12” driver and 13-ply birch cabinet.

Built with heaping helpings of TLC by James Somma and Dan Arango, the Roaring 40 employs a heavy-gauge welded aluminum chassis, Mercury Magnetics transformers, stainless steel hardware, electrolytic capacitors by Sprague and F&T, silver-plated Teflon wire, four JJ EL84power tubes with O-rings and heavy duty retainers, four JJ 12AX7 pre-vamp tubes (and one more in the rectifier), tubular polypropylene signal capacitors, a U.S.-made Eminence Red Coat 12” driver and 13-ply birch cabinet. The top-shelf treatment continues on the amp’s exterior, with a well-executed Tolex application with silver piping accents and a salt-and-pepper grille, along with a minimalist approach to hardware—just a high-quality leather handle and a metal vent; nothing bulky, and no corners.

Aesthetically, the Roaring 40 gives off a definite British vibe, with it stop-mounted controls and shallow (9”) cabinet depth. Controls are straight-forward; on top are a pair of 1/4” inputs (High and Low), Volume controls for the Bright and Normal channels, as well as controls for Treble, Middle, Bass, Presence, Master Volume, and power/standby switches.The back panel has Mix and Dwell controls for there verb circuit, as well as the switchable output selector (20 or 40 watts), speaker impedance selector, fuses, and power cord socket. The control layout is straight forward and has a couple of unique features including blendable Volume controls and the uniquely voiced Presence circuit. The blendable  Volumes let you use as much as each channel as you want on a single input, and mixing the Bright and Normal controls creates tones reanging from bright and thin to thick and fat with varying degrees of gain.

Playing a guitar with single-coil pickups, and with the master Volume turned up all the way (which takes it out of the circuit), noodling with the tone stack (10 o’clock to 2 o’clock) and the Volume controls (9 to 10) reveals harmonically rich British tones with thick mids, tight, round low-end, and clear high-end. With the Volume controls dimmed, the Roaring 40 produces pleasant saturation and overdrive with nice crunch. Blending the Volume controls compensates well when you transition from single-coils to humbuckers; blending more Bright with humbuckers adds chime and a bit of cut, while blending in more Normal adds thickness to single-coil tones.

While the three-band tone stack offers subtle-but-distinct control, the real star here is the Presence knob,which not only adds snap and sizzle when set between 7 and 10, but smooths out the top-end and warms up the overall tone when set between1 and 4. The best way to tweak the 40’s out-put power is by using a combination of the 20-/40-/half-watt output switch and Master Volume. The tone cleans up by simply rolling off the guitar’s Volume control and easing up with the pick. If the amp gets a big loud, rolling off the Master Volume does not appreciably degrade the tone—until you get extreme with it. And its reverb lets you dial in everything from the ultra-wet to subtle ambience. The Sommatone Roaring 40 shines for its overdrive tone, circuit design, a versatile set of controls, and top-notch components.—Phil Feser

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So first things first: an important disclaimer. Modifying an amplifier is serious business, especially when tubes are involved. These amplifiers contain enough voltage inside to kill you, no joke. These kinds of mod kits are intended for people who know what they are doing with electronics. So if you have never used a multi meter (or don’t know what it does) and are not very handy with a soldering iron, these modifications are best left to a professional.

I had heard many good things about the Mercury Magnetics Upgrade Kit for modifying a Epiphone Valve Jr. amplifier. I believe my first encounter with the company was via an ad in Vintage Guitar Magazine (proof advertising actually works!), which prompted a little Internet sleuthing on the subject. My initial searches lead me directly to YouTube, where I found a good collection of demo videos on both the stock Epiphone Valve Jr. and Mercury modified version.

I will say right off the bat that the stock Epiphone (for its price point) is no slouch; it has a good tone for blues and rock and a classic look to it. But after watching some before-and-after videos I was convinced that it would be a worthwhile project.

CAUTION: Any changes in the configuration must be performed by a qualified professional.

WARNING: With a Mercury Universal Voltage Primary power transformer BOTH primary windings MUST be used. Failure to use BOTH windings will damage the power transformer.

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Fender amps with transformer and capacitor upgrades –

Mercury Magnetics transformers in Fender SuperSonic. Note: extra wire is service loop for power suppy board.

The Fender SuperSonic illustrates the high component density of all the circuit boards.

Mercury power transformer with tube rectifier mod in Fender Custom Vibrolux Reverb. No service loop needed.

The cap installed on end due to a lack of room. NOTE: heat shrink tubing & RTV silicone.

Cap upgrade in Fender Super Reverb (Orange Drop -716P Polypropylene Film caps with copper leads).

An additional view of the Fender SuperSonic shows the Mallory type 150M Series – metalized polyester film caps.

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In 1963, the Silvertone 1484 or “Twin Twelve” was top-of-the-line among the amplifiers offered by Sears, Roebuck and Co. It debuted with a whopping catalog price of $149.95 (the equivalent of $1000 today)! Though once headed north of $800 on the latter day collectible market, the economy has seen these tone bandits recently dip back under the $500 mark. The 1484 is one of tone expert Andy Brauer’s all-time favorite amps, and rightfully so, since this baby can rock the socks off the meanest swamp alligators!

Every time someone asks you about sleeper amps, you bring up the Twin Twelve and how it’s one of your favorites. What’s the deal?

Twin Twelves are killer – really magical. Back in the day, you could pick one up at a garage sale for $25 or $50! People sold them as speaker cabinets; they didn’t even know it was an amplifier because the head sits underneath in the cab. It’s an innovative design feature for which we can thank Nathan Daniel; he developed and supplied them to Sears.

How long ago was it they were going for $25?

In the ’70s. But even today, these amps remain very undervalued. Most I see are fairly unmolested and still have the original tubes. They’re clean, or easy to clean because for some reason they weren’t as used or abused as other amps I see in my shop – most have remained closet-classic clean.

Their values jumped, though, when The White Stripes became popular and players learned Jack White’s killer sound was through Silvertone amps.

I agree. He was using a 1485 – the 100-watt version of the 1484, with six 10s. It’s much cleaner-sounding, with more headroom, punchier, with big, tight low-end. Jack liked the clarity – the chimey highs, the thick midrange, and the whoompf on the bottom.

What makes up the heart of the 1484?

It has two 6L6s for power, three 12ZX7s in the preamp, two 6FQ7s for the phase inverter and reverb driver, and a solid-state rectifier. And there’s a funky little reverb tank in them, but most I see are broken.The example on my bench at the moment is from early 1964. Some of the post are ’63, but most are ’64 and the speakers are ’64, which leads me to believe it’s an early-’64 model. The speakers are Jensen C12Qs, ceramic, with 20- to 25-watt capacity. Their small magnetics tend to break up faster and be a little honkier.

Funny, it doesn’t sound like a modern 50-watt amp. More like20 watts.

That’s partly because the voltages on the power tubes – the first-stage plate resistors – are 229k. First-stage plate resistors on the typical Fender amp are 100k.

So the Fenders’ allow more current to flow?

Yes. This results in a lot more headroom, a lot more clarity, and more overall punch. Most modern amps run their tubes, and their entire circuit, hotter than vintage gear. They try and squeeze more bang for the buck out of their amps, sometimes mistaking louder for better.

The nice thing about Silvertone amps, and the Twin Twelve especially, is that by raising some of the resistance, and the way Nat Daniel developed the circuit, results in a very nice note compression that isn’t found in many other amps. The hard edges are taken off the notes. Also, the Twin Twelve’s tone controls are interactive – the more you turn up the Treble and Bass, the more gain you get. So if you want it real clean, turn the Volume to 3 or 4, turn the tone controls down to 2 or 3 respectively and you can get some clarity out of it. But after 3 or 4 on the dial, the amp gets gainier and gainier.

I noticed that the tremolo and reverb affect gain, as well. If you turn everything up, the amp turns into a real monster.It’s not a multi-tasking amplifier. It likes to do reverb, or it likes to do tremolo. If you do both, it gets fussy… but it sounds great, by the way! The 6L6 screen voltage is about 150 volts below plate value, so these amps are not pushing the tubes much at all. When you’re that conservative on the wattage, you reduce headroom. It’s almost like talking a Variac to the incoming voltage. When you Variac it down a touch, you lose clean headroom and get more overdrive.

These amps are not extremely loud, but what they do have is a instantly likeable, friendly tone that really grabs you and kind of encourages you to play with it. It’s very bluesy. It’s aggressive, and it’s compressed, but without the drawbacks of compression. It’s not like a 6V6-driven amp that squashes the sound, it’s more of a high-fidelity sound. It compresses the sound like an LA2A limiter – almost limiting the compression versus squashing it like a 6V6 Deluxe or like a brown Deluxe. The tone stack enhances the tone and adds gain, versus cutting or boosting lows and highs.

So, do you like to just turn everything all the way up on the Twin Twelve?

Who doesn’t like to do that every once in a while on any amp? But no, not as a general rule. Amps that I like, I set the tone controls to five, to start. From there I play with the Volume. And then, believe it or not, I’ll go around the amp with a screwdriver and a socket wrench, and start tightening bolts on the speaker, or tune the cabinet to a certain frequency to get the amp to ring. The Twin Twelve has a ported cabinet with a back panel that’s open on the bottom. One can play with the screws inside the cabinet to torque them all to the same tension, so that sound reverberates off all parts of the cabinet at the same pressure.

Kind of like tuning the head on a drum – you want even tension all the way around…

Exactly. When I do that to a cabinet and the speakers, I hear a difference.

These amps came with 25 feet of cable to separate the speaker from the head. The old Sears catalogue claimed that this was to eliminate feedback. Is there any truth to that?

That was a marketing gimmick. They wanted the musician to be able to place the head near where they were standing, and place the cab away from them, with the idea that the further the cab was from the pickups, the less chance there was for feedback.

Who are some high-profile players who use these?

Obviously, Jack White brought them into the spotlight. But I’ve seen many players – Dean Parks, Ronnie Woods, Keith Richards, Lyle Workman, Josh Homme, Ry Cooder, and David Lindley – use them. It tends to be a staple in major recording studios, so music fans have heard them on countless albums, though they may not be aware.

Do a lot of these amps come in for repairs and such?

I see the 1×12 version, the 1482. And I’ve definitely worked on my share of the 1484s. When I’m servicing a Silvertone, nine out of 10 times it’s merely pitted and dirty and just needs its pots cleaned, and maybe tension the tube sockets or re-solder something for good contact. Generally, the tubes are pretty good, and many Silvertones have original tubes.

Were the Silvertone tubes in these made specifically for Sears?

There were OEM. I’m not sure if they were RCA, GE, or Sylvania, but they were definitely American manufacture. Vintage RCA and GE tubes are considered some of the best, and the tubes in these are terrific. Consider it’s possible to purchase a Silvertones for a few hundred dollars. If original tubes are in there, that’s at least $100 just in tubes!

Are they good for mods?

Not that I’d recommend. Just restore them back to stock.

Other good Silvertones?

The bass version, the model 1483, is pretty awesome. It’s the same circuit minus the reverb and tremolo, and driven through a 1×12 cabinet. It’s 50 watts, as well. Most Silvertones were given numbers as model names, but the Twin Twelve was branded because it was top of the line. The only other amp Silvertone branded was the 1434, which was dubbed the Medalist.

How do the tremolo and reverb sound?

The reverb isn’t the best, but it’s not bad – it’s fashionably anemic. The tremolo is great – very surf-sounding and muted, in a nice way, unlike a Gibson tremolo, which is bright and pingy.

Are there a lot of Twin Twelves out there?

Yes. They were manufactured only form 1963 to ’66, but were apparently churned out in large numbers. There’s almost always one for sale in online auctions, and I often see them in music stores. As I said, they tend to be in fairly good shape, though if exposed to moisture the particleboard tends to fall apart. Aside from that, there are no major issues. They don’t always ship well, though – the reverb tanks can get messed up. But there’s nothing that can go wrong on these that can’t be fixed; all the parts are readily available. If you blow the transformer, a Mercury Magnetics replacement is available.

Another interesting feature is that if you open up the back panel on the speaker cab, you’ll see there’s a hidden shelf. It’s a baffle.

What for?

It’s a bass trap, for lower frequencies. When the bass comes off the back of the speakers, the baffle catches it and sends it forward again. You get a little bit more of a thump than with most open-back cabs. It was really kind of a revolutionary design Nat Daniel came up with, and I don’t know of any other amps that employ it. (Ed. Note: Daniel had a patent on the speaker cabinet design with inclined baffles called the “acoustical case”.)

Sonically, what would you compare this amp to?

Probably a Fender, as it has a really nice twang. But it’s a bit darker. It offers a terrific Dick Dale surf tone as well.

Cranked up?

Well, listen to any White Stripes album!

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Amp Transformers, Output Transformers & Chokes

Early ’60s Power Transformer

Mercury’s Exclusive Tonal Satisfaction Guarantee:

Your complete tonal satisfaction is our only goal. All Mercury Magnetics® APS®, Axiom®, ToneClone®, and Radiospares® products come with a Tonal Satisfaction Guarantee. If you are not satisfied with any Mercury Magnetics® transformer or choke, for any reason, you may return it within 30 days for an exchange or refund (minus all freight). See “Exchange or Refund Policies” below for addendums.

Mercury’s Limited Workmanship Warranty Policy:

Mercury Magnetics® warrants its non-OEM transformers to be free from defects in material and workmanship, if properly installed, under normal use for a period of TEN (10) YEARS from the date of purchase, and by the original owner. Note: this warranty does not cover damage caused by external sources or user error. Defective transformers will be replaced or repaired at our discretion. To the extent permitted by law, the foregoing is exclusive and in lieu of all other warranties or representations whether expressed or implied, including any implied warranty of merchantability or fitness. In no event shall Mercury Magnetics® be liable for special or consequential damages. All warranty returns are examined by our engineering staff to determine the exact cause of failure. This warranty is void if your transformer has been tampered with. See “Exchange or Refund Policies” below for addendums.

Shipping Info:

• All shipments are F.O.B. Chatsworth, CA

Exchange and Refund Policies:

• For warranty inquiries on Mercury-made OEM transformers, please contact the manufacturer.
• Please contact Mercury Magnetics® to discuss making an exchange or to obtain a refund within the thirty (30) day guarantee.
• Insure your shipment for the invoice amount.
• Include the original or a copy of the invoice.
• All transformers must have their identity stickers intact.
• CODs will not be accepted. Ship prepaid. If the product is found to be defective or in the case of a shipping error, we will issue you a refund for shipping costs.
• Keep a record of your shipment until you receive your credit or replacement.
• Returns or exchanges are accepted within a 30 day grace period.
• Custom Shop orders or Mercury Vintage (restorations and/or rewinds) are covered by the Workmanship Warranty but not our Tonal Guarantee.
• Wrong parts sent to you due to errors on our part will be replaced or credited at your option. Return freight for that product will also be credited.
• Do not cut the lead wires until you have tested and listened to the installation. Before cutting the leads, solder and bolt the transformers in, and try them out. When you are satisfied, cut the leads and complete the installation. Cut leads to the transformer will incur a 20% restocking fee. For a refund the product must be returned in salable condition without damage or cut lead wires.
• Transformers that have been tampered with, modified, or with unauthorized attempted repairs will be rejected. Please package all product carefully.
• No credit will be issued for less than $5.00US.
• The use of any type of attenuation device on any Mercury Magnetics transformer will void the 10-Year Warranty. Using “dummy load” or “power attenuators” damages transformers. These type of products wear out power tubes at an accelerated rate, and in some cases may cause RF to be generated in the output, which may destroy the output transformer.
• Discontinued, obsolete or closeout sale items will not be accepted for return unless they qualify under our warranty.
• The Mercury Tonal Satisfaction Guarantee and 10-Year Warranty is only extended to transformers and chokes of our upgrade kits. Mercury assumes no responsibility or liability for the amp or the work done to the amplifier.

No one has ever succeeded in deciphering the infinite variations manifested by the human mind — how we inhabit the same world, yet perceive and react to every moment in our lives in such profoundly different ways. Society, education and culture provide filters intended to shape how we view the world, but each human being remains different and unique for reasons that remain a mystery. And so it goes with music and musicians…. Why do some players find their voice in a Stratocaster, while others can’t imagine playing anything but a big-ass hollow body? This is “me,” and that isn’t, but for someone else it is. Most of us hear target sounds in our head that drives our selection of instruments and gear — a sound that may change with each song, while a weekend blues player might simply wish to refine a single, signature tone in the style of Jimmie Vaughan or Albert or B.B. King. The point is, we often know where we want to go, but the shortest path to our destination isn’t always so clear. To make things more interesting, some players just want to be dropped off at the right address in the Quest for Tone, preferring to find something that works with no tweaks or modifications as quickly as possible, while others view the Quest as a journey with no defined beginning or end. To them, anything is possible until proven otherwise, they enjoy exploring new sounds, and their “failures” are often as illuminating as their successes.

We learned this lesson once again with an amp that we had initially written off, only to discover four years later that it could become one of the most extraordinary guitar amplifiers we have ever owned or reviewed. What changed? Well, with the lucid, unerring clarity of hindsight, we had to dream it first, thinking of terms of possibilities — what could be, rather than focusing solely on what was missing….

Fender ’57 Twin

The 25 watt Twin originally debuted in 1952 as the first amp with separate bass and treble controls. By 1955, the model 5E8 Twin had been upgraded to 50 watts, featuring two 5U4G rectifiers — another Fender first in guitar amplification — dual 6L6s, bass, treble and Fender’s presence control, a new fixed bias power transformer, choke, and extra gain stage and second negative feed-back loop, and the new “narrow panel” cabinet with speakers mounted in each corner. In the next circuit revision (1956–57 model 5E8A), a ground switch was added and the treble tone circuit was removed from the negative feedback loop. Leo Fender couldn’t play a lick on the guitar, but he obviously never stopped thinking about how to improve the sound and performance of his amplifiers, as evidenced by the nearly constant revisions and refinements of Fender circuits. The mighty “high power” 80 watt Twin model 5F8 appeared in1958 with four 5881s, a short-lived 83 mercury vapor rectifier that would be replaced by a single GZ34 rectifier (model 5F8-A), and a new “Middle” control added to the normal bright volume, bass, treble and presence controls. For many collectors and players who can afford them, the high powered Twin ranks with the 5F6-A Bass man as the most toneful, desirable, rare and costly Fender amps ever built.

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Question: Can changing an amp’s OT create more clean headroom?

Answer: Changing out an OT with a tranny that has the same impedances as the one being replaced won’t deliver more power because volts-is-volts and watts-is-watts. Meaning: no extra power is delivered here for free.

You can force out more power from a tube by lowering the primary impedance of an OT. This usually does more harm than good, shortened tube life and harsher tone for starters. A player can get more out of his amp like extended clean tone headroom and a noticeable presence of a bigger soundstage effect by way of transformer solutions. By increasing an OT’s “tank capacity” with more of the right kind of iron and copper resulting in more inductance to the primary winding. It’s this inductance that has a more profound effect on tone and how large it sounds that goofing around with starving tubes with lowered impedances.

OTs that are physically larger in size do sound larger even if they may have the same impedance as their smaller counterpart. The reason for this is the energy carrying the guitar tone information through the tranny is seeing less power-robbing resistances and going through its magnetic field transformation with faster responding iron helps the tranny to have a larger window for tone to flow through.

The same holds true for the PT. While the OT benefits the player with extended headroom and frequency range, the PT supplies more energy and the quicker delivery of it to the amps circuit resulting better bottom end and improved note dynamics in the form of note attack and separation.

This is also why amps that run hotter than a bitch kitty usually don’t have good tone as well.

Source: https://mercurymagnetics.com/pages/_misc/FAQ.htm#Clean_headroom

Marshall’s famed 1960s “plexi” and early-’70s 50-/100-watt amps gained notoriety for their fantastic tones. Of course, the downside was that they had to be driven hard to sound their best, which to the player (and anyone else in a milewide radius) meant volume – a lot of volume. And that sometimes meant turning speaker cabinets toward walls or employing an impromptu blanket muffler, sacrificing tone for the sake of band harmony and/or the mix. Then there was the consistency factor from one amp to the next, which meant hunting down the best-sounding Marshalls became an expensive game.

In short, when it comes to plexi tone, maybe those weren’t the “good old days.” Perhaps now, in our world of reissues, reproduction, and boutique guitars and amplifiers, guitarists are indeed in the midst of a golden age. If you doubt that’s the case, let us introduce the Voodoo Amplification V-Plex.

Voodoo Amps was founded in 1998 when hardcore tone lover Trace Allen Davis, a professional guitarist and proficient guitar/amp/pedal fixer, began modifying amplifiers. Largely dissatisfied with the offerings of the day, his idea of good tone caught on, and he quickly earned a reputation as a capable, comprehensive amp repair/modification shop.

We were offered a listen to the 50-watt V-Plex with Voodoo’s propriety-design 4×12″ slant cabinet. The hand-wired V-Plex is a four-input/two-channel amp with three 12AX7 tubes in the preamp and two EL34s in the power section. It has a single set of controls for Presence, Bass, Middle, Treble, Master and Volume – a layout identical to that of a vintage non-master-volume Marshall. The V-Plex’s Master volume is placed between the phase-inverter tube and the power tubes, which gives the player the ability to dial in plexi-like distortion starting at a very reasonable volume. On/off and standby switches, along with a red indicator, also occupy the front panel.

A look inside reveals flawless workmanship and top-quality components. Davis is, as we said, very much about the look and feel of guitar tone, and the research he put into this head is glaringly obvious. The cabinet uses four Celestion G12M “greenback” speakers, which are seen in amps all over the place.

But Voodoo’s cab is a little tricked out; aside from its propritary internal design, it is also capable of operating at either 4 ohms or 16 ohms in mono, as well as 8 ohms in stereo.

No doubt about it – the V-Plex talks the talk. But to see whether it walked the walk, we recruited a Schecter 006 solid body with two high-output humbuckers, and a Fender Stratocaster with three Duncan Alnico single-coils. We plugged in the Schecter and started with the V-Plex’s controls set in a familiar plexi manner; Bass at 10, Presence at 4, Mids at 6, Treble at 2, Master between 8 and 9, and Volume pushed to 8.

Flashback

If you’re a fan of the original Marshall JTM 45/50/100 models (if you’re a fan of real rock guitar tones, that’s you!), plugging in the V-Plex could well be the ultimate experience, especially if you’re not hip to coughing up the money to obtain (and hassle to care for) a vintage Marshal. Tone – gain-rich harmonics, with that clear, articulate crunch we’ve come to lust after – spews from the V-Plex by the truckload.

To test the effectiveness of the Master volume circuit, we rolled off the Master and brought the Volume control up a touch, and heard fistfuls of rich gain at reasonable SPLs. Yes, Virginia, you can get great plexi tone at comfortable levels.

The tone knobs reacted almost exactly like those in the original plexi circuit in that they don’t alter the tone much, but produce different textures. Backing off the volume and increasing the Master yielded a cleaner crunch that never surrendered its true character. “Jumping” input channels (a favorite trick of four-input-Marshall owners) substantially fattened the tone.

We next plugged in the Stratocaster. To keep high-end response where we liked it required rolling back the Treble and Presence controls, but the Strat also proffered fat, meaty tone from every pickup and selector-switch position. Crossing channels again, we got more meat right up until we pushed it too hard, when (in true plexi form) the signal compressed beyond the point of being enjoyable.

If you’re after the ultimate vintage plexi tone, your search could very well end right here, as the Voodoo V-Plex delivers definitive plexi tone, and has the ability to play at comfortable levels. Davis and his crew nailed it. – Bob Tekippe/Ward Meeker

VVT’s Lindy Fralin Model amplifier

Maryland-based amplifier builder Vintage Vacuum Tube Amplifiers (you may know it as VVT) recently fielded a request from renowned pickup winder Lindy Fralin. He wasn’t looking for advice on wire or how hot to wind a pickup for best interaction with a particular VVT; rather, Fralin wanted an amp built to his specs and taste. And not just for him, but for the mass market. VVT, realizing the co-branding possibilities, jumped at the opportunity.

So, what does a tone guru like Fralin want in an amplifier? Well, he says the goal was “a clean, full-body-voiced amp that’s lightweight and able to sound good at low volume.” Sounds like something we’d like, too. So when VVT asked whether we wanted to hear it, we were happy to take up the offer.

At first glance, the VVT Lindy Fralin amp looks boutique in a way we’ve come to expect; i.e. it sports point-to-point wiring with carbon-comp resistors, an all-tube circuit, and a 12AX7-driven spring reverb and preamp. But, go deeper and you’ll quickly discover some seldom-seen features, like a trick self-biasing-cathode design that allows the player to switch between a pair of 6L6s (for 30 watt of output) and a pair of 6V6s (for 15-watts) without having to re-bias the amp. Part of its secret is a custom-wound Mercury Magnetics transformer designed specifically for the Fralin that allows the amp to switch between the 6L6s and 6V6s while maintaining stable impedance for the tubes and speaker load.

The amp ships with a pair of 6L6s, but will also accept 5881s or JJ 6V6s, for an altogether different favor. Another unique feature is Fralin’s choice of a single 15″ alnico-magnet Weber speaker instead of the more traditional pair of 10″ or single 12″ speaker.

The overall look and layout of the amp is different, as well, but still boasts a vintage vibe with a neatly executed off-white tolex, oxblood grille cloth, top-mounted controls, and heavy-duty leather handle. There are no metal or plastic corner protectors, and no extraneous piping or badging. Its look is clean, simple, and classic. The control layout is accordingly succinct, with a single 1⁄4″ input, a switch for Bright, and controls for Volume, Treble, Bass and Reverb, along with switches for Power and Standby. Also worthy of mention is the 11-foot power cord.

VVT shipped our tester with a matched pair of 6L6s by TAD and a matched pair of 6V6s by JJ. We started with the TAD 6L6s and our test guitars – a Fender Relic Strat and a Hofner Verythin Classic with mini-humbuckers. After plugging in the Relic Strat and letting the amp warm up, we set the Volume at 3 o’clock, Bass and Treble at 12, and then we hammered a few chords.

We were immediately impressed with the amp’s complex overtones, its round, punchy low-end response, and its snappy highs. It didn’t take much noodling or knob tweaking to realize that the tone controls on this amp, along with its Bright switch, are exceedingly well-voiced. From a player’s perspective, that means it’s easy to find likeable sounds. The Bright switch compensates nicely for the slightly darker sound of mini- or full-size humbuckers, while the wide sweep of the Bass control keeps its frequencies full and punchy with single-coils.

While the amp is voiced for clean tones, it also does a good job when it comes time to get dirty, and is very responsive to changes in pick attack or guitar output. Simply backing down the volume control on the guitar and easing up on our pick attack, the Fralin cleaned up from moderately dirty overdrive with musical overtones to a sparkling clean sound that didn’t lose any of its life or attitude.

We popped in the matched set of JJ 6V6s and checked the tone at 15 watts output. The amp broke up quickly and had a slightly more boxy sound, with reduced complexity of overtones; still very lively and punchy, just not as big as 6L6s – fantastic for low-volume situations. The tube-driven reverb is also well-voiced. At lower settings, it adds a bit of ambiance that doesn’t get in the way or wash out the amp’s tone, and at higher settings it’s suitably splashy.

The boys at Vintage Vacuum Tube do a killer job on the Fralin signature amp. It’s loaded with big, dynamic, single-coil-friendly tone (that sounds pretty good with humbuckers, too!) in a nice, lightweight package. – Phil Feser

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Seen the price of a vintage Marshall Plexi lately? Your three grand won’t guarantee a virgin circuit or great tone, but if real Plexi tone is what you’re all about, you can get there for a lot less, guaranteed. When TQR Advisory board member and Sheryl Crow guitarist Peter Stroud decided to make a Plexi from his late ’70s fawn 100W head, we enlisted the capable assistance of our main toneman Don Butler and the team at Mercury Magnetics, home of
the ToneClone line of authentic vintage-style replacement transformers. Mercury has blueprinted and reproduced nearly every vintage transformer made for guitar amplifiers, and they can rewind any blown transformer to exact, original specs and sound. So settle back and enjoy the following discussion and review of Peter Stroud’s successful conversion of a common (they built 1,000s) Marshall 100W into a stellar 100W Plexi.

TQR: What is the origin and general history of this Marshall amp?

Peter: I bought this amp about 10 years ago with the matching straight-front 4×12, 100 watt cab from a dealer down in Texas. It’s a ’77 Super Lead 100 watt 4-input. I was big into collecting the f awn-colored Marshalls at the time – a poor man’s custom color. Around the same time, I had learned how to work on my own amps from the standpoint of preventive maintenance and tone tweaking, so I converted the amp over to a cascade-style master volume circuit like a late ’70s head or JCM800. Eventually, I missed having the 4-input sound and put it back to its original wiring.

Don: This amp was a standard 100 watt, non-master Marshall from the late ’70s. Some mods had been done and then undone. A few coupling caps had been changed as well as a few resistors

Strengths: Semi-loud. Typical PCB Marshall from this era. Better quality glass board than what’s used now.

Shortcomings: Ceramic caps. This amp was voiced for brighter sound, less bottom, and quicker distortion onset that original ’60s versions didn’t employ. It still had a couple of the original filter cans. The amp sounded exactly the same no matter what guitar was plugged up to it – no tonal distinction between any instrument at all! Very over-emphasized, weird G string odd harmonics (most likely old filter cap related). I have to add from a personal note that this was the worst sounding Marshall I’d ever heard or played! In a word – no tone!

TQR: Describe the specific improvements that you wanted to make to the amp, both from a technical perspective, and sound-wise. What components were changed and why?

Peter: I don’t know why – from my monkeying around with it perhaps (laughs), but this Marshall just sounded like crap. Every time I plugged in I would end up turning it off – totally uninspiring. I replaced tubes and a cap here and there but resigned to the notion that it might be the transformers. I had replaced all of the power supply caps, but not the 50/50mf in the preamp circuit. It could have been that – who knows? But in any case, I would have thrown it on eBay had it not been for the color. Instead, I decided to make it a guinea pig. I’ve been messing around inside my amps again recently and have had a real desire for that 100 watt Plexi sound and the cleaner, fuller tone they deliver. This head was far from it! Having read the ToneQuest interview with Sergio about Mercury Magneticstransformers and poking around their website, I figured the fawn 100 watt would be the perfect amp for a conversion – change out the transformers for high voltage models reminiscent of the Plexis and wire it up exactly like a ’67. I was determined to demystify the whole Plexi thing once and for all for my own comfort. After seeing how Mercury Magnetics had “cloned” the power and output trannies of an old Plexi, I felt the missing link had now appeared. Then you stepped in and it mushroomed into a topic for ToneQuest, and a very deserved one indeed. Nothing better than to see if any Marshall can become a Plexi, especially since the latest prices on eBay for Plexis are more than I care to spend. I need amps that are bulletproof and easy to replace. I spoke with Sergioand Paul at Mercury and they eventually hooked me up with Don Butler. I was thrilled to have Don take over the job knowing his ear for tone and knowledge of Plexis. There were three CD’s I used as a tone reference: bootlegs of Cream in ’67 and Jeff Beck in ’68, and the Hendrix at Monterey Pop Festival album.

Don: Peter wanted the amp to sound like a mid-to-late ’60s Plexi 100 watter. More specifically – a ’67. I replaced all the little green (or were they grey?) ceramic caps with polyester tubular caps and replaced any resistors that needed to be changed with carbon comp types. Polyester caps were used in the ’60s in all Marshalls for the main tone and coupling caps. I know for the higher value caps in the pico farad range, Marshall generally used the ones from Lemco or RS that were a flat mica-looking cap covered in a baked on ceramic or wax dipped coating. I used silver micas for those in Peter’s amp. I like the smoothness and more transparent quality of silver mica. The original polyester coupling and tone caps that Marshall used in the ’60s were from a company in the Czech Republic called Iskra. I believe Phillips imported those to the U.K. Those are the ones everyone refers to as the mustard caps. I used Mercury’s Plexi 100 output tranny, 10H choke and 100W Plexi power tranny that provides the B+ with around 525V DC after rectification. In my humble opinion, Mercury makes the best sounding, most accurate and most reliable clone transformers on the planet.

I also used the FRED rectifiers in place of the little cheap-o IN4007 diodes for the rectifier. I like the way they smooth out the harshness of the treble frequencies and take out that mid range bump that’s common with a solid state rectifier in amps. They also seem to add more note clarity, harmonics, and detail to the sound and tone of an amp. I replaced the components, transformers and the remaining filter cans. I then converted the circuit to what was used in 1967 in terms of how it was wired and component values.

Really, it’s not much. On the first valve/tube you remove the wire coming from pin #8 and shorten it and solder it to pin #3. The cathodes on that tube were shared and went to an 820 W resistor with a 250mf @ 25v cap paralleled with it to earth/ground. The second valve/tube did not have a cathode bypass cap in those days – only the resistor. There was a .68 cap I removed from that spot. I also removed the .004 cap from the volume pot on channel #1. That cap makes the amp distort quicker, and usually at just “2” on the volume pot you’re out of clean headroom and well into distortion land. That’s not what Peter wanted or what the old amps were like. I also used two 0.1/ 600V caps coming out of the phase inverter vs. the .022/600V caps that Marshall started using in around ’69 to brighten up their amps.

On the later Plexis you will find a 500rf and 33K slope resistor on Lead models and a 250rf & 56K slope resistor on Bass & PA models. Most, if not all of the schematics I’ve seen for early 100 watt Plexis used the 250pf & 56K in the tone stack. Peter’s amp had the 500rf and 33K. I replaced the 33K with the 56K for more bottom and hit a mid point between the 500rf & 250rf and used a 390rf cap for the treble control. Not too bright and not dark. With Some Lead amps, you have to turn the treble off and even then it can still be too much. I’ve found that by using a 390rf you get a happy medium point where the treble pot is still useable. All I did was put the amp into what Marshall’s circuit was in 1967 and used the same values and type of components they used, with a few improvements like the FRED rectifiers.

TQR:What type and brand of tubes were selected and why?

Don: I used the Svetlana EL-34s, as I’ve found them to sound extremely close to what the old Mullard xf3s offered in tone, as well as reliability. I’ve compared them side by side in my old 50-watter and in my ’64 VoxAC-50 and it’s really close. Preamp tubes – I used the new Ei Elite gold pin 12AX7s. To me they sound very nice and close to old Brimars and Mullards. Don’t forget that the Phillips Electronics Corp. once owned Mullard and Ei among many other subsidiaries. Ei seems to have made an excellent attempt at creating a good sounding, reliable 12AX7 that they pre-test before sending out. My favorite 12AX7-type of valve/tube for Marshall’s are the Brimars, as they offer a bit of that aggressive old tone that Marshall’s are famous for.

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In this issue we are dealing with a subject on which I have received many inquiries in the past. It is about the selection or matching of tube amps for the best possible Jazz sound. Amplifying acoustic or semi-hollow-body guitars has always been a huge challenge because most jazz guitarists are very demanding in terms of sound and simultaneously fight against unwanted distortion and feedback. In the following article I would like to summarize some tips and tricks that get  great tone and how to avoid distortion.

When I started getting involved with jazz sounds, around 1977, most guitarists in this genre used transistor amplifiers. George Benson played a Polytone, Pat Metheny an acoustic amp with a 4×10” speaker cab and Volker Kriegel and Michael Sagmeister used a Gibson LAB L9 with 15” speakers. Such examples can be found very often from that period. Although all of these guitarists had indeed very good tone, the typical depth and openness of a tube amp sound could not be reached however in its wider spectrum. Still the transistor amps had some advantages over tube amps: They sounded very compact and linear, were less prone to feedback and offered a relatively balanced frequency spectrum and a nice sustain, which was the ideal sound of many jazz guitarists. A Gibson L5 played through a LAB or a Polytone is completely convincing – even today.

One disadvantage that the transistor amps had in particularly was its dynamic behaviour, in their relatively poor response and in their tendency to not let the individual character of a particular guitar fully unfold. You could also say: Transistor amps tend to standardise tone.

I do not wish to start a discussion about tube versus transistor because transistor amplifiers will continue to play a rightful role in jazz. It is more about ways to show how one can get the typical warm jazz tone with a tube amp without all the disadvantages.

Above all I am thinking of the sounds of the early sixties, which were marked by numerous jazz guitarists including: Wes Montgomery, Kenny Burrell, the early George Benson, Herb Ellis, Joe Pass, Barney Kessel, Grant Green and Jim Hall. All of these guitarists were playing tube amps on their early recordings and getting fantastic sounds. Today tube amps are celebrating a renaissance with jazz guitarists.

Let us first take look at the most popular models from the distant past. In the fifties the combos from Fender (Tweed), Gibson, Standel or Flot-A-Tone were especially loved by jazz musicians due to their sound and their small size. These amplifiers were sufficient for jazz guitarists because they were usually accompanying musicians and they performed as a soloist only in rare cases. They often stayed in the background and did not play very loud.

Even back then, most jazz guitars were equipped with a tone control that made it possible to filter out unwanted peaks and thus to form the typical dark jazz sound. But soon the guitar became a solo instrument. Just think of the impressive sound of a cascading Les Paul, who at that time had good reason to play on a solid body. The traditional jazz players remained with their hollow bodies and now had to fight against all the disadvantages of the electrification of their sounds. Recently I read in a retrospective of Wes Montgomery that he alleged that during his entire career he was unhappy with his sound because he simply could not find the perfect amp. One might even go so far and assume that the dark jazz sound is actually created only (and eventually cultivated) because the amount of unpleasant highs tube amplifiers have, are rather imperfect sounding and also quickly led to feedback. Most guitarists wanted more of a linear and natural reproduction of their beautiful instruments that already sounded great acoustically.

Let’s now take a look in the interior of a tube amp and consider certain circuit characteristics which can be modified for a better jazz tone. The objectives of these measures are the reduction of distortion and the high frequencies, improving the mid-range and increasing the linearity of the sound.

First, a list of known suitable amplifiers for conversion to a “jazz box”: Fender Tweed Fender amps from 1956 and Brownface, Blackface and Silverface combos. Examples from this list shall be explored in following issues.

Let’s start with a Tweed Deluxe amp replica from Cream which I have converted for jazz sounds. These amps are known for their distortion when left stock and therefore not ideal for a clear jazz tone. But they are very small and handy and with around 15 watts of power ideal for use in a club. In addition, these amplifiers are connected with a so-called “split-load” phase inverter which is appropriate for our purposes because of its low gain. The only drawback is the two coupled volume pots, which restrict the volume control range on the one hand and deliver too much gain in the preamp. The aim is to reduce the gain in the preamp and increase the output power and stability of the amplifier. Only then we get enough headroom for a clear sound.

Just this once, I should like to “put the cart before the horse” because there are a number of measures to improve the amp without intervention on the circuit.

First, these amplifiers usually have an inefficient speaker. Powerful speakers with a good efficiency rating are especially suitable for jazz sounds. Those who love the Alnico sound can search out an old JBL D-120 and replace the aluminum dust cap with a counterpart out of fabric (available from Weber VST). The speaker can be helped dramatically in the highs and we get a warmer, rounder tone. Excellent was also the old Fane Crescendo Heavy-duty speaker, which is also suitable after the removal of the aluminum dome making a perfectly clear and powerful sound. These speakers were also used by David Gilmour. Another excellent choice is also an Electro-Voice 12L or a Jensen C12K with 100 watts. All these speakers better the sound of the Tweed Deluxe significantly. You only have to watch out for the thin baffle-board because vibration during transport could for example pull heavy speakers from the screw holes.

A further stabilizing method is the conversion of the power tubes to 6L6 or 5881, which I recommended at this point several times. Although the amp has only about one or two watts more output, the increase in headroom is very clear. You get more clean reserves and dynamics. Here I recommend changing the cathode resistor of the amplifier from 250 (typically with 5 watts) to 330 ohms with 10 watts. If you play a jazz guitar with humbuckers, we recommend the low input of the normal channels. Here there are less highs and the output signal of the guitar is more attenuated. It should be noted that the volume pots affect each other on the Tweed Deluxe. By turning the unused channel by not more than 70 percent, the tone is much cleaner, but also quieter.

If you don’t wish to utilize this trick, you can simply remove the cathode of the second stage capacitor (Elko 25mF/25 volts) and reduce the gain of this stage substantially, which in turn increases headroom. The amp will be clearer and somewhat linear, but also a touch softer.

Even more clear sound can be obtained by replacing the output transformer. Something I always do in such tuning. In this case I choose a Mercury Magnetics Tweed Pro Axiom FTPRO-O transformer (available at Tonehenge Amplification) with 8 ohms, which gives much more stability to a small tweed amp.

If you want to use the amp only for jazz, you can also decouple the two volume controls from each other and only one channel and a tone control remain. Now you can adjust the volume much finer and linear. The circuit can be found at www.schematicheaven.com under Fender Deluxe 6G3. Here the channels are completely separate, each with their own volume and tone control. It’s only after the volume knobs on the channels that two 220k ohm mixing resistors are mixed together again.

Since the Tweed Deluxe played with humbuckers has in general somewhat bassy sounds, I also reduce the value of the coupling capacitors from 0.1mF to 0022mF. This makes the sound tighter and more mids. Sprague “Orange Drop” P715-type fit perfectly here.

Finally we get to fine-tuning via preamp tube placement. With a good 12AY7 and a 12AX7 of your choice, you can continue to shape your favourite tone. For those of you who have not had enough, you can play with the value of the capacitor on the tone-pot. The Deluxe was originally installed with a 0005 UF capacitor but also possible are values such as 0.01mF or 0.02mF (as in the 6G3) for a slightly warmer tone. If you want to darken the sound one can bridge one of the anode resistors at the 12AY7 with a 0.003mF capacitor (as in the normal channel of the Brown Vibrolux).

The result is a truly compelling jazz amp for small clubs, feeds back less, offers more clean reserves and could compete with any Polytone but all the benefits of dynamic and harmonically rich tube sound can be enjoyed. Diana Krall’s guitarist Anthony Wilson often used a Tweed Deluxe replica from Clark and his blond Gibson Byrdland in the studio. This sound is very reminiscent of Kenny Burrell and offers a wonderfully unique character. Have fun experimenting!

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After a hiatus of 45 years or so, Fender has been carefully re-entering the business of building hand-wired tweed amplifiers with the resurrection of the narrow panel ’57 tweed Twin and the ’57 Deluxe. Of course, there are scores of small amps that have been inspired by the Deluxe, and many more 5E3 knock-offs being built today in the “subbooteek” cottage industry comprised of solo solderers who build in their spare time and often put their work up on eBay. For some cost-conscious players, a tweed Deluxe for $600–$800 is a deal that cannot be refused—even if the amp was wired up by an unknown tonehead on a basement workbench in Akron. But Fender is Fender, and while they chose to ignore the thriving boutique market for hand-wired tweed circuits that blossomed in the early ’90s with the appearance of Victoria, they have not forgotten how to put an amp together, and in the case of the Deluxe sent to us for review, it stands apart from all the rest with a very unique voice.

We asked Fender’s Shane Nicholas and Sergio Hamernik at Mercury Magnetics to explain the process of natural selection that evolved during the development of the ’57Deluxe….

TQR: Describe the process in which your design team evaluated various vantage examples of the 5E3 Deluxe, and how widely the actual sound of the vintage amps you listened to varied, specifically?

Shane:There are several guys here at Fender who own old amps, and we also have friends who do. When we were ready to begin the’57 Deluxe project, we brought in a few original vintage examples, and a couple of “boutique” versions of this type of amp. We listened to all of them with various guitars, and listened to each amp chassis hooked up to the others’ cabinets. Keep in mind that every amp—especially 50-year-oldones, will sound a little different than another one of the same model. It’s pretty well documented that Leo Fenders some times changed components “on the fly,” while the official schematic documentation would be updated later. My old Deluxe might have been built with some different stuff than yours, even though they were both “stock” 1957 5E3models. Then add in aging, abuse, repairs, etc., and it’s a wide target that needs to be narrowed. For example, we had one amp here that was much more distorted sounding than the others, so unless you are only laying 1951 Howlin’ Wolfstuff, you probably wouldn’t like that amp as much. For me, the ideal is an amp that gives a beautiful clean tone with the volume set low, and a dirty, harmonically rich tone with the volume set high. You should also be able to set it on, say, “5” and control the amp’s distortion by simply varying your pick attack. We decided that one of the old ’57s was the most desirable example of a 5E3 Deluxe, and we used it as the golden sample.

Once we got to this point, project engineer Nick D’Amato really got down to business. The final schematic and components we chose were basically picked so the prototype would sound as close as possible to our golden sample amp. Obviously, we use new parts, not 50 year old stuff from a flea market or whatever. We also had to make a few changes in order to pass modern worldwide safety regulations; things like shielding, ground wires, and the three-prong power cord, which negated the use of the old ground polarity switch. We put a Standby switch in its place, which is a good thing. These changes don’t really affect tone, but they do reduce hum and improve playability.

We also decided to go with 12AX7s in the preamp, even though the originals were designed with the 12AY7 in the front end. Our thinking was, not only is the 12AY7going to be tough for us to get in quantity, but many players in fact prefer the 12AX7s higher gain. If you are playing ZZ Top stuff, for example, you’ll probably prefer this. The12AY7 will work, however, so some owners will buy one and stick it in their amp.

The transformers are also a crucial piece of the puzzle. We auditioned quite a few prototypes, and some of them were too efficient or too distorted, etc. One of the vendors we contacted was Mercury Magnetics, whom we’ve worked with in the past They sent us five different power and output samples, each based off an original transformer set found in a vintage Deluxe amp. During A-B tests, one of these closely matched the OT in our golden sample amp. We worked with Mercury to make a few tweaks, and soon we were positive we had the right transformers.

TQR: How many different types of speakers did you consider?

Shane: Well, the original Jensen in my old Deluxe really sounds and looks perfect, like you’d expect. We found that the new Jensen P-12Q sounded close enough, so we stopped looking. In my ten years at Fender, I have discovered that no matter what speaker we supply in a tube amp, a certain percentage of customers are going to try something else. Celestion, Jensen,Eminence, and boutique guys like Weber all have their supporters and detractors. It’s human nature to tinker with your machinery, and a speaker swap is one of the easiest mods you can do to an amp.

Now, having said all that here’s where it gets fun. One of the boutique amps we tried happened to have a Celestion Blue Alnico speaker in it, and it sounded very good. So we tried that speaker with our prototype 5E3 amp, and said,“OH MY WORD!” I had heard that speaker before in different amps, but this combination was stunning. The amp became a lot louder, for one thing.We thought for a minute about using this speaker in the ’57 Tweed reissue, but it’s not really the authentic, original sound or look. It’s also a lot more expensive. So, we remained sold on the Jensen, but when we developed our limited edition, black lacquered version—the Fender 57 Amp—we decided to equip it with the Celestion Blue.

TQR: What are the unique challenges involved in building hand-wired amps, compared to those with a printed circuit board?

Shane:Making it look and perform like the old amp while using readily available parts that we can buy in quantity. I am a stickler for performance, but if our customers didn’t care to look inside, we wouldn’t worry about the looks of the components and wire so much. For example, Alexander Dumble told me he likes our new ’57 Deluxe, and was surprised that we used such heavy wire in the chassis, as it’s really not necessary. We can’t pass modern safety regulations using cloth wire, so we got the next best thing. I’d also like to mention that, while we build higher quantities of hand-wired amps than all the other boutique builders, it’s still a very small number compared with the number of PCB amps we build, like our Hot Rod series and all the sold-state models. Our factory estimates about eight times the labor in a Vibro-King versus a ’65 reissue amp with a PCB.

TQR:We would assume that Fender has a separate group of employees devoted to building the hand-wired amps.

Shane: We do have the hand-wired team in a separate area in the factory. They are highly trained, patient employees who take a lot of care with these amps. Most of them are women, same as Leo’s day, maybe because they tend to be more patient than us dudes. And women’s hands tend to be smaller, making it easier for them to run wires and solder connections in the tight confines of the amp chassis. I don’t know the training regimen off hand, but I believe many of them cut their teeth on guitar wiring before moving on to amplifiers.

TQR: With the tweed Deluxe in production, are there plans to develop additional hand-wired Fender models of the past?

Shane:Yes. The list of great old Fender amps begging for reissue is a long one!

In case you don’t know, Mercury is known for having acquired and cloned hundreds of stellar vintage transformer sets that com-prise their ToneClone and Radiospares series…

TQR: How did you become involved with the development of the 5E3 specifically?

Sergio: It call came about as a follow up to the ’57Twin-Amp reissue project that we were a part of a few years ago. Mercury designed and supplied Fender with the transformers for those amplifiers, which was a very successful endeavor—so much so that Eric Clapton made them his main amps for his own tours and the Cream reunion tour.The momentum started by the ’57 Twin-Amp project quickly created a demand for some sort of follow-up amp in this positive vibe, and Fender’s decision to reissue the 5E3tweed Deluxe came as good news to us. It is probably the most copied circuit on the planet, and I couldn’t think of abetter project to sink our tranny designer teeth into.

Years ago the late Ken Fischer, of Trainwreck, told me that the Deluxe was an early inspiration for him to get into amp building. He went as far as to refer to the Deluxe circuit as the cornerstone of the boutique market. It’s a truly different dynamic when the company that started it all wants to reintroduce a benchmark in amplified guitar tone, and especially when their goal is to make the amp sound as fresh as it did when it was first launched. We’ve worked for decades acquiring our extensive library of transformer designs that originate from variants of pre-production to pilot runs of many vintage amps, so amplifier companies often consult with us because we’re a small but dedicated group just nutty enough to be the conservators of such things.

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OK, so perhaps you’re sold on snatching a stock Pro Junior, but of course, you want it to sound the best it possibly can…. Should you wish to dig a little deeper in the quest for tone, veteran amp builder Ben Fargen has developed a line of Hot Mods for stock production amplifiers – lots of them, including the Pro Junior, and we asked him to describe the inspirational behind his concept for the Hot Mods….

“For a number of years I had a lot of people wanting me to work on their vintage Fender, Marshall and Vox amps, and I really never had the time until the economy slowed down in 2008. A local customer asked me to take a look at a Marshall JCM800, which (laughing) really isn’t the kind of amp I’d usually be interested in, but I agreed to look at it, got in touch with Mercury Magnetics, went through the schematic, and wound up turning it into a really great sounding high-gain amp that would appeal to people who like that sound. I had also done some design work for Carvin when they wanted to optimize a production design and get the most out of it, so when the economy slowed down I began taking in specific camps to upgrade, and from there we started developing mod kits. Customers went just their chassis in, which isn’t expensive to ship; we do the work and ship it back.

Through the later part of last year we were doing about one mod project a day, at first taking in just about anything, but we’ve since whittled it down to specific amps like the Pro Junior, Blues Junior, Blues Deville and the reissue blackface Deluxe Reverb, for example. With these amps it’s not the design that’s the problem – it’s just that the component selection is based on what is most practical and economical for an affordable production amp. We take those amps and optimize the sound as if production cost was not an issue, and we have customers who have had two or three different amps modded now, because they are basically getting a boutique amp and the tone that comes with it.

TQR: In the Pro Junior specifically, what areas of the circuit do you focus on for the mods?

There are really only so many ways to wire up a tube amp circuit, and in most cases we’re focusing on the same key areas in each amp – plate resistors, coupling caps in the EQ and phase inverter, and slop resistor for the EQ, and cathode resistors and cathode bypass caps are huge and often overlooked…. We hone in on the tone-shaping improvements that give us the biggest bang for the buck, and of course the Mercury transformers make a big impact. You can do any of these mods alone and improve the sound, but it’s really the cumulative benefit of using specific high quality components and the Mercury Magnetics transformers that determine the end result where you really hear the magic. We aren’t the only people doing mod kits, but you’ll notice that we use specific brands and types of caps and resistors in very specific places with our mods, and that’s the result of my having build amps for 12 years and learning what specific types of components are going to do in a particular part of the circuit.

TQR: You also added a power supply choke in the Pro Junior you modded for us….

We add the choke because it is so critical to what I call pick dynamics – the note response to pick attack, and improved sustain. Most budget amps just have a power resistor separating the B+ and the screen voltage – it works and does the job, but the correct choke in a circuit really adds a huge amount of that ying and yang you want to hear between the power amp and the preamp.

TQR: And what is the cost of the Pro Junior mod as you’ve done this amp?

With the full Mercury transformer set it’s $499 without a speaker swap. All the Hot Mods are in the $349 to $549 range until you get into 100 watt or JTM45 Marshall reissues and things like that. We’ve also done a lot of mods for the reissue Bassman…. As you know, there is nothing like a great Bassman, and there are a few revisions that Fender made that are just not happening at all, but when you get rid of those they can sound fantastic.

Here’s the deal…. You economically ship your chassis per Fargen’s instructions and they ship it back fully optimized. We asked Ben to send us a Hot Modded current production Pro Jr. for review and we directly compared it to our stock 2001 Junior, fully loaded with our NOS tubes and Jensen Vibranto. The modded amp Ben sent included stock Groove Tubes and a new Celestion Greenbackten.

As soon as we played through the Hot Modded amp, we heard the same dominate midrange push and lack of treble presence we had heard at first in our own amp. Less pronounced with brighter single coils, yes, but still too middy for our taste, so we subbed in the JensenC10Qfor the Greenback and the angels were singing again – sopranos, altos, tenors, and baritones all present I the choir. In fact, both amps sounded similar with the stock tubes in the Hot Mod Pro and our stock model with the NOS tubes – thick, rich and very smooth with excellent dynamic response and full, clear fidelity. Fargen’s Hot Modded Pro Junior possesses smoother, warmer overall tone while our Pro still sounds brighter and a little glassier overall. We suspect that a bias pot and lower voltages would tame the intensity of the distortion, but the 5751 does a nice job as an easy workaround. Fargen’s amp was also a little quieter at idle than ours, although we hadn’t noticed this until we had a quieter amp for comparison. For more information on all of Fargen’s modifications, check out the Hot Mod pages on the web site.

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THE CREW AT 65 AMPS HAS A REPUTATION for putting considerable R&D sweat into every new amp design before it leaves the maker’s Los Angeles, California, headquarters. The Lil’ Elvis has, in the broad sense, been in development even longer than most — a stately 48 years or so, if you take into account its roots in an odd little combo owned by Vox collector and author Jim Elyea, one that Vox designer Dick Denney had built as his own personal amp, but which never went into production. Having seriously dug this prototype’s overdriven sound, 65 Amps’ Dan Boul and Peter Stroud set about tidying up the circuit, giving it a usable clean voice and a much broader vocabulary, and making it into a versatile — yet still quite simple — club-gig and studio amp for the contemporary tone fiend. The result is 65’s most diminutive offering yet, both in physical stature and output level, but as we shall see, the stated “clean output” of 12 watts can be deceiving, and this isn’t the mere bedroom brawler that such a rating might imply.

The format hints at a blend of American and British small-amp templates: from this side of the pond, a quirky split-phase inverter similar to that of Fender’s Princeton Reverb and a “bias wiggler” tube tremolo circuit not unlike that used by some Gibson and Ampeg models — from the other side of the pond, the dual EL84 output tube complement and EZ81 tube rectifier. And from California circa 2009, plenty of fresh thinking in the form of the Bump and Master Voltage circuits and the squat, chunky cab, as well as the considerable effort that went into transformer design (with Mercury Magnetics), grounding and filtering topologies, and noise reduction techniques. The Lil’ Elvis is also a somewhat simpler affair than other 65 products, and comes in at a little less coin as a result. Its Bump feature is fixed — rather than having its own Tone and Level controls like the one on the SoHo and Stone Pony — though it is footswitchable (from a pedal that also includes a stomp button for the tremolo), and EQ is limited to a single Tone control. There’s also an enigmatic Smooth switch that has no noticeable affect on clean settings, but does exactly as it says when you crank the amp up, by engaging a circuit that keeps the grid from lifting up from ground when you go into heavy distortion, thereby reducing crossover distortion at the output stage. The final control on the panel, labeled Master, actually governs a proprietary “master-voltage” circuit that lowers the preamp and power tubes’ output levels while retaining filament voltage and, hence, is purported to preserve tonal vocabulary and playing feel.

The stout 21″ wide x 18 high ” x 11.5″ deep cab wears the traditional 65 Amps two-tone cosmetics with aluminum front-edge cooling vents, and houses a single Celestion G12H-30 speaker. Inside, the workmanship lives up to everything I’ve come to expect from this high-end maker, offering a superb example of handcrafted tube amp manufacture. Of the whole package as it sits, my only minor gripe might be that it’s tricky to change the horizontally mounted tubes, requiring a blind grope inside the cab, but it’s easy enough flip the whole chassis outward, panel still attached, to do the job more carefully. Oh, and why “Lil’ Elvis”? In Boule’s own words: “No matter how small you make Elvis, he still rocks.”

I tested the Lil’ Elvis with a Fender Telecaster, a Collings 290 with Lollar P90s, and a Gibson SG with humbuckers. Played clean, it issued classic blackface-Fender-style tones, with piano-like lows and silky highs, with good headroom up to higher Volume settings than I would have expected. Cranked up, this sonic template segues into a surprisingly convincing Marshall half-stack impersonation. There’s a juicy midrange that isn’t over-baked, surprisingly solid low-end thump, and velvety smooth highs that really help your lead playing to soar — especially with the Smooth switch engaged. Stomping on Bump makes everything thicker and bigger, enabling serious rock lead and rhythm work alike from this deceptive little amp. And although it would be nice to be able to set the amount of extra boost that this feature introduces, it’s still a groovy option. The Master control works as it should, retaining body and character as you lower the output level, but it does increase the depth of your given tremolo Intensity setting, an unexpected quirk, but one that’s not too problematic given that you’ll most likely adjust it and leave it — and likewise set Speed and Intensity to taste — before you launch into playing. For its own part, this output-bias modulating tremolo circuit is a real sweetie, adding rich, chewy, chop to your sound and attaining a sense of depth and vibe at higher Intensity settings that must be heard to be appreciated.

Containing a few nods to classic amps of the early ’60s, but tied together with a lot of original design work, Lil’ Elvis is one chunky bundle of surprises. This top-notch tone machine is surprisingly versatile despite its simplicity, and it sounds way bigger and badder than you’d ever imagine 12 watts could provide. So if you’re gunning for a low-power amp that wields some serious mojo, Lil’ Elvis is the ass-kicker you’ve been waiting for.

SPECS:
CONTACT 65 Amps, (818) 760-5089, 65amps.com
MODEL Lil’ Elvis
PRICE $2,150 retail/street price N/A
CHANNELS One
CONTROLS Volume, Tone, Depth, Speed, Master, Smooth switch, Bump switch
POWER 12 watts
TUBES Three 12AX7 preamp tubes, two EL84 output tubes, one EZ81 rectifier
EXTRAS Series effects loop, two-button footswitch jack, dual speaker outs, switch for 8Ω & 16Ω impedance
SPEAKER Celestion G12H-30 (16Ω)
WEIGHT 49 lbs
KUDOS Great build quality. First-class clean and overdrive tones. Surprising versatility.
CONCERNS Tubes are tricky to change without removing chassis; tremolo strength increases as Master Voltage is decreased.

Source: https://mercurymagnetics.com/pages/news/GuitarPlayer/GPDec09.htm

A few years ago the guitar playing community experienced a resurgence of low-wattage amps. I’m not sure if it was because of the weight or the sheer volume larger stacks delivered, but the search was renewed for amps that could provide the same tone at an easily manageable weight and sound levels that didn’t make bartenders/engineers/wives scream, “Could you turn that down?”

This brought renewed interest in an obscure Marshall amp, the model 1974, an unassuming 18-watt combo. Originally available as a 1×12 — and closely related to the 18-watt model 1958 (2×10) and model 1973 (2×12) combos — the amp featured two EL84 power tubes, three ECC83 preamp tubes and a 6CA4 (EZ81) rectifier tube. There was even a rare reverb-equipped model, but all of the amps featured both a normal channel and a tremolo channel. The magic of the model 1974 was that with just a Les Paul and a cable players could approximate the beloved Eric Clapton “Beano” tone used on the Bluesbreakers with Eric Clapton album. Although I should note that Eric actually relied on a JTM45 combo, interest in the Beano tone ensured the 1974’s place in guitar lore. As was to be expected, clones of this amp began popping up rapidly once the originals, now extremely rare, began fetching prohibitively high prices.

I was fortunate enough to have quite a bit of exposure to these early Marshall amps, having worked with a shop that had no less than six of the model 1974s in stock during my tenure. One exceptional example was retained for studio use. A number of renowned guitarists had used the amp over the years, and they all agreed that it was one of the best — if not the best — they had heard.

A few months ago I was invited to Houston, Texas, by guitar legend Billy Gibbons, to bring a 2×12 Marshall model 1973 to the studio for a new ZZ Top album. Billy is an avid fan of 18-watt amps and has numerous clones to choose from, in addition to two original 18-watt Marshall combos. While we were listening and comparing sounds, I noticed a green Tolex 2×12 combo called the Retro-King 18 Watt sitting in the studio. Once he plugged into it, I knew both the original of the tone and that I had to check one out for myself.

King for a Day

The Retro-King 18 Watt is a completely custom-built amplifier, with the features you would expect to see in an amp of this class, including a solidly built, Baltic birch cabinet and handwired point-to-point construction. The fit and finish on everything from the cabinet to the Tolex covering was impeccable. The model I tested for this review had a 12″ Mojo Tone British Vintage Series speaker, although builder Chuck Dean will install others by request. The entire enclosure is substantial and provides for a big box tone from a single speaker combo. An impedance selector is included which is great for those planning to use this amp with other speakers or additional cabinets. The transformers are custom-wound to original Radiospares specs (an optional Mercury Magnetics transformer is available by request).

The 18 Watt has a couple of different features that I found to elevate this amp above some of the other 18-watt clones currently available. First, is the Master Volume control. You may ask why a Master Volume is needed for a low-wattage amp; while it does function to reduce the volume when the amp is cranked (bringing us back to that whole bartender/engineer/wives problem), it more importantly regulates how hard the power section is hit by the preamps. How the power section is driven affects everything, including the tone, overdrive and response of the amp, making the Master Volume a critical part of the circuit. The 18 Watt’s Master Volume circuit does not feel or respond like other Master Volume circuits I’ve heard; this one allowed me to get a wide variety of classic 18-watt tones, as well as the sounds of other model 1974 clones on the market. The Retro-King also features a tube biased tremolo like the original — it sounds wonderfully authentic, deep and a little Voxy. A footswitch proved to not only turn the tremolo on and off but to select between two speeds.

The second unique feature packed into Retro-King’s 18 Watt combo is a switch that allows for the selection of a tube rectifier or solid-state diode. The diode setting, while obviously not an original Marshall feature, provided more definition and headroom than the tube rectifier. When tube rectified, this amp has that sweet sag and compression that blues players love. If a player buys this low-wattage combo but is more accustomed to larger amps, this innovative feature will make it fee4l a bit more familiar — definitely a nice touch.

Of course, not all potential users of small amps are blues players. As a matter of fact, when I hooked the amp up to a Marshall Guv’nor pedal and set it for a very clean, high-headroom sound I was rewarded with a great rock sound. The tone was similar to Gary Moore, or even a bit more intense than that, if needed. The amp’s overdrive without a pedal ran from Black Crowes territory to the always-wanted, rarely granted “Beano” tone. Also surprising was that a Strat sounded excellent through this amp — something that I haven’t consistently found in other clones. The harmonics are rich, a la Billy Gibbons, especially when using pick harmonics. The 18 Watt cleaned up nicely and captured my picking dynamics perfectly.

The Final Mojo

I found the Retro-King 18 Watt 1×12 to be louder than the real thing, but with an authentic rendering of the actual tone for which these amps are famous was always there. I was also able to get higher-headroom, punchier tones that I was not able to get with the original. The original produced a slightly more compressed tone when driven hard with humbuckers but this would not have been obvious if the original had not been sitting right beside the Retro-King. In fact, the tones were so similar that I would have been guessing which one was which in a blind taste test. All in all, the Retro-King is more versatile than most other 1974 clones, without sacrificing the reason one buys an 18-watt Marshall-type amp in the first place.

Source: https://mercurymagnetics.com/pages/news/PremierGuitar/PremierG-12.htm

Source: https://mercurymagnetics.com/pages/news/GuitarPlayer/GPAug07.htm

Workingman 8004 / Power 750 — #067163000

Workingman 8004 / Power 750 — #0067220000

Many of you are already familiar with our resident amp tech, studio owner/engineer and advisory board member Jeff Bakos. In his spare time, Jeff occasionally builds amps for clients on request, and lately he’s been asked to build… you guessed it – small little biters. Since his personal GA-5 has been featured so often on various recording projects, Jeff toyed with the idea of recreating the Gibson GA-5 Skylark for a minute, but given the fact that vintage GA-5s remain fairly plentiful, he ultimately decided to design his own simple take on a smallish amp – the 8 Ball. Housed in a Mojo Champ cabinet, the 8 Ball is built with one of our favorite tens, the Eminence Legend Alnico 1058 (that’s a hint), Mercury Magnetics trannies and choke, and premium components, including Sozo coupling caps. With the bigger Mercury Princeton transformer set, the single 6V6 / 12AX7 / 5Y3 design is capable of producing 10 watts of power. Features include dual inputs, volume and tone controls, a front panel line out jack, and a “vintage” / ”modern” toggle switch also conveniently mounted on the front panel.

The “vintage” setting produces pristine Fendery clean tones up to 12 o’clock on the volume control, gradually followed by a progressively thicker growl with intense distortion and sustain. In this setting, the 8 Ball surpasses all the other small amps we’ve reviewed in terms of practical versatility with stronger, louder clean tones and a more gradual It’s back! We are now resuming limited production of our meticulous recreation of the original 1959 DeArmond R15 1×12 amp. You may recall that we initially produced a limited number of TQ Clarksdale amps in 2006, before our supplier for the original chassis informed us that small runs would no longer be possible. We’ve found a new supplier, and the TQ Clarksdale “DeArmonds” will be built again by Jeff Bakos with our original specs – pin cabinet construction and design identical to the original, original Mercury Magnetics Tone Clone transformer set cloned from our original ’59 DeArmond, hand-wired chassis, premium components including Sozo caps, Celestion G12H 70th Anniversary speaker, premium JJ and Tung-Sol tubes, Evidence Audio speaker cable, custom gold grill cloth and blonde Tolex covering. This 22 watt design represents one of the rarest and most toneful combos ever built. The original 1959 DeArmond 1x12s were built for just one year in Toledo, OH, and a clean example recently sold on eBay for $7000. In 2006 Jeff Bakos meticulously blue-printed our original DeArmond, Mojo created CAD drawings from the original cabinet design, and we sent the transformers to Mercury Magnetics to be cloned. The result is a phenomenal 1×12 that will generally kick any tweed Deluxe straight to the curb with a bigger, bolder voice and lush, musical distortion cranked. The 4-input, cathode-biased Clarksdale can be operated with dual 6V6s and 5Y3 rectifier for optimum burn, or a pair of 6L6s and 5AR4 for slightly more power and clean headroom. Blonde Tolex only, simply because it’s the coolest color…

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Amp Transformers, Output Transformers & Chokes

C12 Microphone Power Supply Transformer

Did you know that the transformers and chokes in your amps are aging? If your amp is 20 years or older you really need to know this. Over time, the materials that were used in the construction of these transformers have changed — actually degraded, and become increasingly fragile. Before the “smoke gets in your eyes” hang on to your power cord and don’t plug in just yet until you understand the following.

Basically, transformers can be broken down into three components. The first being “copper,” which is what the wound coils inside and the lead wires are made of. The second is “steel” which is what the stack of metal plates in the core are made from. Third, and most important to overall life expectancy, is “insulation” whose function is to keep things alive and running properly by not letting the other components touch each other and/or conduct when they are not supposed to. A breakdown with any one of these components will eventually grenade your amp!

Copper by itself doesn’t really age, but the thin, clear coating of insulation around it does in the form of microscopic spider web cracking. This will lead to high voltage break down in the winding. Lead wires are also susceptible when their vinyl or cloth jackets become old and brittle — sometimes causing arcing through the cracks and splits in the insulation. Phantom clicks and pops heard through the speaker are also telltale symptoms of aging.

Steel can degrade over time and extended use, especially if contains traces carbon. Carbon is a contaminant and has no positive contribution towards tone. The older the amp is, the higher the possibility. When that happens, the core begins to be less conductive to magnetism (magnetism is the essence of how transformers work!). Symptoms of that occurring include higher transformer operating temperatures, general dulling out of tone with the absence of treble frequencies, fuzzy mids, and a noticeable softening of the bass notes. None of which has anything to do with rust. Remember, rust on your core is a helping friend. For more information on this check out the article “Transformer Rust—Friend or Foe?”

Insulation is where most of the aging problems lie. The older your amp is, the more likely its transformers were wound on paper tube bobbins — with Kraft paper as its insulation (which is no different than the paper used to make shopping bags at your local grocery store). This material has a tendency to suck up moisture and retain it. Moisture alters the delicate balance of reactive values in the transformer throwing off your tone into less interesting domains. The more destructive side to this moisture absorption is that it harbors mold and bacteria which consumes the paper, further diminishing its insulating properties. Even if this material has avoided moisture altogether, it will eventually crumble into dust over time.

Are all vintage amps time bombs? Certainly not. But to be safe don’t play Russian Roulette with your valuable, irreplaceable, and highly-prized collectible vintage amps. If your amp hasn’t been fired up in years, don’t just plug it in and flick that switch on. You risk seeing your investment go up in smoke.

If you are in possession of a Variac, a volt meter and a current meter then you have the necessary tools to properly and carefully ramp up the input voltage while monitoring the current draw. This will also help reform the filter caps as well as avoid the “smoke test” with your transformers. If you don’t know what any of this means then we strongly recommend getting an amp tech to do it for you. If you don’t know of one, call us and we’ll help you find one qualified to do the job. When the fuses in your amp keep blowing it is your amp’s way of telling you something’s wrong and to take it to a professional.

One of the most important services Mercury Magnetics has to offer is free to all customers. We will evaluate your transformers with the most thorough and advanced testing. We do this at no cost providing you cover the shipping costs to and from Mercury. Transformers with no fault found are sent back to be reinstalled in the amp with a least the knowledge and confidence that things were double-checked. Transformers that failed in testing are either rebuilt/restored or replaced with ToneClones®. Free estimates are always given in advance. Either way you leave satisfied with the confirmation that your original works fine or the problem can be fixed.

Source: https://mercurymagnetics.com/pages/_misc/FAQ.htm#When_the_Smoke_Gets_in_Your_Eyes

You’re are of the phenomenon… Suddenly a guitar, amp or some other new or pre-historic gizmo seems to come out of nowhere to achieve white hot, must-have status. The same thing can happen with previously unknown builders, too. Take Marshall 18W “clones,” for example… For the past 3-4 years these recreations of the rare originals were hot, hot, hot, with small custom builders sprouting and thriving from within the 18W Discussion Page. This was good for builders, good for players, and an unanticipated consequence was spawned — the rapid expansion of the cottage industry providing small amp builders with custom-made chassis, capacitors, transformers, cabinets, and just in time, an expanded range of guitar speakers developed by Eminence and Celestion. By the time Marshall jumped into the game with their own hand-wired 18 and 20W amps, the custom-built 18W wave had begun to crest and break, but there is now a new ripple on the horizon that we predict will soon form a formidable new wave among custom builders — the Vox AC30. Granted, Korg has already issued their own limited edition version of a hand-wired AC30 following the success of the British-made Vox AC30 TBX reissue, and we have reviewed the AC30 Custom Classic in this issue with backup color provided by The Radiators’ Dave Malone. While the Custom Classic is a very affordable and perfectly respectable alternative, it would be unreasonable to expect an economically built, mass produced amp to seriously rival a vintage JMI AC30 in original condition that has been competently serviced by an experienced tech. What about the original Matchless DC30 built by Mark Sampson? Great amp, but not the same. Players craving the authentic sound of an original AC30 have four choices today—find an restore an old JMI, buy a reissue and play it as is, have the transformers, caps and resistors in the signal path of your reissue amp upgraded, or buy booteek.

Well, it’s one thing to lovingly resurrect the rather Spartan Marshall 18W circuit, and quite another to tackle the original JMI design, which is much more complex, costly and labor-intensive. Furthermore, some builders may succumb to the temptation to significantly “improve” the original AC30 circuit. That would be a mistake. The successful builder will locate a vintage AC30 with truly bitchin’ tone (assuming they are capable of identifying said bitchin’ tone) and build more, per the specs revealed by blueprinting the old one. As far as we know, this has yet to happen on a meaningful scale. To date, we have located one potential candidate built by DST Engineering that will be reviewed next month. If anyone reading this believes there are more, please let us know.

Meanwhile, let’s address the common belief that 45 year old Vox amps are too unreliable — dangerous, even — for ecstatic thrashing, let alone regular gigging. While it is true that the design of the AC30 (and AC50) provide precious little ventilation (the top vents are stingy at best), we have seen AC30s used by touring musicians and there were no flames shooting from the back (Daniel Lanois didn’t even bother with a backup). So we asked ace amp tech Don Butler (Toneman) to precisely describe the steps he takes to make a vintage Vox roadworthy…

Don Butler: Vintage AC-30s suffer a lot from neglect. People are under the misunderstanding that all you need to do to any vintage amp is replace valves/tubes occasionally, but it requires much more than that. Here’s what I do when I get an AC30 or AC50 in for service that hasn’t had anything done to it since the day it left JMI in Darford, Kent…

Replace the dual 16uf @ 500v can, replace the 32uf @450v cap in the supply line that goes from the bottom power amp section to the preamp, and replace the dual 8uf can in the pre-amp. Replace the 32uf @ 450v cap for the Top Boost circuit (if the amp has integral Top Boost). Replace all the 25uf @ 25v cathode bypass caps (I see a lot of Vox amps where all of the main filters have been replaced but not the cathode bypass caps. It’s really just as important to replace these as well, as they set the gain for each area of the circuit they’re in). While I’m at it… Electrolytic caps have a lifespan of 7 to 10 years. After 10 years they start to deteriorate and slowly affect the way your amp functions (and not for the better, either). If you have an amp that 35-45 years old with original filters in them, well then, you’re asking for a lot of problems by not changing them. I’ve had a few vintage amps where the filters were not changed and they eventually shorted, taking the output tranny or choke of the mains tranny with them. To me they’re cheap insurance to keep your amp working properly and sounding good. By the way, the worse thing anyone can do to any amp is not turn it on for at least an hour a month. That keeps the electrolyte in it’s liquid form and prevents it from drying out and crystallizing.

Back to JMI-land — replace the output section cathode bypass cap (250uf @25v) and the four 100 ohm resistors on each EL-84 socket. These almost always drift way out of tolerance. Use 1 2att 100 ohm carbon film. On any voltage path resistor that needs to be replaced, use a carbon film. But, in the signal path, never use anything but carbon comp, otherwise it won’t sound the same. Vox always used carbon comps for everything. These days you can get 5% tolerance carbon comp resistors — in the sixties you were lucky to et 10%, and most used + or – 20% resistors.

Check each resistor with a meter. If the resistor is more than 20% off, replace it. Check the output tranny. Measure the primary side from center tap to each anode. The center tap is always soldered onto the main supply filter can. Be sure to discharge the cans before you do this!! The anodes are hooked up to pin #7, and they should read very close to each other from the center tap to each anode. Each era had different readings. A Haddon output transformer has a different primary reading than a Woden and different from an Albion as well.

Clean each valve socket, input jack and pot with Caig DeOxit D-5 contact restorer. And here’s a bit that is as important as everything else — make sure every nut, bolt, screw and pot nut is tight. You would not believe how much you can improve the noise and hum in an AC30 simply by doing this. I’ve had amps where every one of them is loose! On the 12AX& that is used for the Normal and Brilliant channels., JMI used a wire from pins 4 & 5 to ground to keep the filament supply grounded. Cut this wire off from the pins to ground. Take two 100 ohm resistors and attach them from each side of the filament supply at the pilot lamp to ground. This is what Fender did for years to make the filament supply quiet. It’s an easy “center tap” for the 6V AC filament supply.

Check all your valves/tubes. Always use a matched set of EL-8rs and good 12ZX7s and a decent 12AU7. Spend the money for a good rectifier! You have to look at the cost of valves as an investment in your tone. Good preamp valves should last at least 10 years for NOS. I’ve seen many Ac30s with perfectly working Mullard GZ-34s that were 40+ years old. EL-84s get beat-up pretty good, but still important to buy quality valves. This is also important: With any and every JMI Vox Amp, use a Variac! Why? My wall voltage reads anywhere from 114v to 122v A.C. Vox amps want to see 105v to 110v MAX! The voltage selector may say 115v, but Sergio at Mercury Magnetics has told me many times that the real input voltage of old JMI amps was 110v max. If you plug your AC50 into the wall at 1222v, instead of your B- supply reading 470v like it should, you’ll get over 500v D.C. Most of the components are rated at 400v-500v max. By putting more in you run the risk of shortening the life of most of the components if not frying them outright. If you follow this advice and servicing recommendations and use a Variac, you should have a happy AC30 that will work for you for years without trouble. It doesn’t hurt every few months to tighten up all the screws, nuts, etc. If you tour or gig with an old AC30, you have to know at least a little bit about how to maintain your amp. If you’re too lazy to do that, then buy a new Custom classic and send it to me to mod into one that sounds very close to a JMI-era amp. There’s a good book you can get from a guy named Stephen Grosvenor in the U.K. called “A Service Engineer’s Guide to the Vox AC30 Valve Amplifier.” This just came out in June (’06).

TQR: Not all power tubes can take the heat that Vox amps produce. What are your favorite choices for output tubes in old AC30s and AC50s and do you have any suggestions for keeping these amps running at lower temps?

Don Butler: AC30s — Tungsrams and Polem/Telem (same manufacturer — these are made in Poland) for NOS and EI Elites for new tubes. The Tungsrams are very clear, open sounding with nice chime on the top end and a good tight bottom. Same with the Polems, but the Polems have a bit more midrange. I find Mullards very dark and flat by comparison. I’ve tried just about all the NOS EL-84 types in my Voxes and Marshall 1974X. The EI Elites are a great sounding tube but lack just a bit of the detail and harmonics of the NOS. Still, a great sounding tube compared to the rubbish that’s being made these days.

TQR: You’re known for upgrading stock “reissue” amps. Describe the typical upgrades and modifications you make to reissue AC30s and the most recent AC30 Custom Classic.

Don Butler: I replace the output tranny with a Mercury Magnetics clone, same with the choke, as the choke is a very important piece of the puzzle. I replace every resistor and cap in the signal path with carbon comp resistors and Sozo caps. I have an audio “break-in” CD that I run into the amps after I’m done. About 4-5 times simulates the amp having been played for around 80-100 hours. I do this because every output tranny takes around 20 hours to break in, and the Sozo caps take around 100 hours to break-in. This way when my customer gets their amp back it’s as if it’s already been played for a bit and should be more open and touch responsive than if it hadn’t been played. I do also play through them when I’m done. I have to make sure they sound right. I play them again after I run the CD through them, and it’s fun to hear the actual difference!

Source: https://mercurymagnetics.com/pages/news/ToneQuest/_2007/TQRJan07-1.htm

Maryland-based amplifier builder Vintage Vacuum Tube Amplifiers (you may know it as VVT) recently fielded a request from renowned pickup winder Lindy Fralin. He wasn’t looking for advice on wire or how hot to wind a pickup for best interaction with a particular VVT; rather, Fralin wanted an amp built to his specs and taste. And not just for him, but for the mass market. VVT, realizing the co-branding possibilities, jumped at the opportunity.

So, what does a tone guru like Fralin want in an amplifier? Well, he says the goal was “a clean, full-body-voiced amp that’s lightweight and able to sound good at low volume.” Sounds like something we’d like, too. So when VVT asked whether we wanted to hear it, we were happy to take up the offer.

At first glance, the VVT Lindy Fralin amp looks boutique in a way we’ve come to expect; i.e. it sports point-to-point wiring with carbon-comp resistors, an all-tube circuit, and a 12AX7-driven spring reverb and preamp. But, go deeper and you’ll quickly discover some seldom-seen features, like a trick self-biasing-cathode design that allows the player to switch between a pair of 6L6s (for 30 watt of output) and a pair of 6V6s (for 15-watts) without having to re-bias the amp. Part of its secret is a custom-wound Mercury Magnetics transformer designed specifically for the Fralin that allows the amp to switch between the 6L6s and 6V6s while maintaining stable impedance for the tubes and speaker load.

The amp ships with a pair of 6L6s, but will also accept 5881s or JJ 6V6s, for an altogether different favor. Another unique feature is Fralin’s choice of a single 15″ alnico-magnet Weber speaker instead of the more traditional pair of 10″ or single 12″ speaker.

The overall look and layout of the amp is different, as well, but still boasts a vintage vibe with a neatly executed off-white tolex, oxblood grillecloth, top-mounted controls, and heavy-duty leather handle. There are no metal or plastic corner protectors, and no extraneous piping or badging. Its look is clean, simple, and classic. The control layout is accordingly succinct, with a single 1?4″ input, a switch for Bright, and controls for Volume, Treble, Bass and Reverb, along with switches for Power and Standby. Also worthy of mention is the 11-foot power cord.

VVT shipped our tester with a matched pair of 6L6s by TAD and a matched pair of 6V6s by JJ. We started with the TAD 6L6s and our test guitars – a Fender Relic Strat and a Hofner Verythin Classic with mini-humbuckers. After plugging in the Relic Strat and letting the amp warm up, we set the Volume at 3 o’clock, Bass and Treble at 12, and then we hammered a few chords.

We were immediately impressed with the amp’s complex overtones, its round, punchy low-end response, and its snappy highs. It didn’t take much noodling or knob tweaking to realize that the tone controls on this amp, along with its Bright switch, are exceedingly well-voiced. From a player’s perspective, that means it’s easy to find likeable sounds. The Bright switch compensates nicely for the slightly darker sound of mini- or full-size humbuckers, while the wide sweep of the Bass control keeps its frequencies full and punchy with single-coils.

While the amp is voiced for clean tones, it also does a good job when it comes time to get dirty, and is very responsive to changes in pick attack or guitar output. Simply backing down the volume control on the guitar and easing up on our pick attack, the Fralin cleaned up from moderately dirty overdrive with musical overtones to a sparkling clean sound that didn’t lose any of its life or attitude.

We popped in the matched set of JJ 6V6s and checked the tone at 15 watts output. The amp broke up quickly and had a slightly more boxy sound, with reduced complexity of overtones; still very lively and punchy, just not as big as 6L6s — fantastic for low-volume situations. The tube-driven reverb is also well-voiced. At lower settings, it adds a bit of ambiance that doesn’t get in the way or wash out the amp’s tone, and at higher settings it’s suitably splashy.

The boys at Vintage Vacuum Tube do a killer job on the Fralin signature amp. It’s loaded with big, dynamic, single-coil-friendly tone (that sounds pretty good with humbuckers, too!) in a nice, lightweight package.

The term “imitation is the sincerest form of flattery” has particular meaning in the music industry, where popular guitars and amplifiers have long been used as templates for the creation of “new” brands. This is particularly true in the boutique amplifier market, where probably 99 percent of currently available models are based on classic designs by Fender, Marshall, and Vox. Given that reality, it’s inevitable that some of the more recent amp builders who have managed to innovate and create truly original sounds will also see their designs cloned to one degree or another. The raison d’etre for copycat products is typically that demand for the real thing outstrips the supply, or that relatively few can afford to purchase the authentic product. Both are true of the amplifiers made by Howard Dumble, and the fact that the vast majority of guitar players will never get closer to one of his Overdrive Specials than the front row seats of a concert makes it no surprise that a small number of builders offer their own takes on that extremely rare and expensive amp (we’re talking around $30,000 these days). One of those is Fuchs Audio Technology, which with its Overdrive Supreme (a name that can also be conveniently abbreviated as ODS) makes no attempt to conceal where it draws its inspiration.

But Fuchs has packed plenty of cool things into this amp that any tube freak could appreciate. A peek inside the aluminum chassis reveals a mix of neat handwired and PCB circuitry, chassis-mounted pots, jacks, and switches (the mini toggles reside on one of the three PC boards), and chassis-mounted sockets for the four Svetlana 6L6GCs, two Ruby 12AX7As, and two Groove Tubes GT12AX7Ms. For low noise, the tube filaments are heated by regulated DC voltage, and regulated high-voltage supplies the preamp stages. The fan-cooled amp sports a high-quality Mercury Magnetics output transformer, and biasing adjustments are facilitated by the addition of bias trim pots and test points for each output tube.

Controls

Not that the Overdrive Supreme is overly complicated, but a few of its functions warrant explanation. In basic terms, this amp consists of Clean and Overdrive channels (or preamps), both of which feed a common set of tone controls, a reverb, and a Master volume. The Gain knob adjusts the amplification level in the Clean preamp, which in turn feeds the Overdrive preamp when you switch to distortion mode. Then there are three Overdrive controls: an internal (but user adjustable) trimmer that determines the amount of signal flowing from the clean preamp into the first stage of the Overdrive preamp, an Input knob that sets the amount of distortion (by adjusting the drive level between the two pairs of overdrive stages), and an Output control that’s essentially a lead master volume. This combination of controls gives you the ability to precisely tailor the amp’s gain stages to suit your guitars, pickups, and playing style.

The Overdrive Supreme also has a number of switchable functions that affect its tone. The Brite switch operates on the Gain control to provide a boost in treble (which diminishes in effect as the knob is turned beyond the halfway point), the Deep switch shifts the overall tonality of the amp to emphasize lower frequencies, and the Rock/Jazz switch alters the range and depth of the tone controls to provide for more gain and a more aggressive EQ in the Rock setting, or a smoother, more neutral response in the Jazz position. There’s also a Mid-Boost pull function on the High control that shifts the range of the circuit to emphasize midrange and a Gain-Boost pull function on the Mid control that bypasses the tone controls to increase gain on both channels. Lastly, turning up the Accent control reduces negative feedback at higher frequencies in the power section to increase edge and sustain.

Supreme Tones

Auditioned with several different speaker setups (including Marshall 2×12 and 4×12 cabs and a Celestion-loaded Dr. Z 2×12), the Overdrive Supreme never failed to impress. The closed-back Dr. Z cab worked particularly well with this amp (the cab’s width was a perfect fit too), and Fuchs also offers a matching 2×12 loaded with Fuchs FAT-1S speakers ($695 retail/street N/A). But even driving two 12s, the Overdrive Supreme is a loud amp that seems to find its “sweet” spot at levels that would be overkill in a small club. You can tame the blast with the Master Volume, but as this amp struts its stuff best when let off the leash, you might want to consider one of the lower-wattage Supremes if you don’t regularly gig on big stages (head and combo configurations are available in power ratings from 30 watts to 150 watts, and at prices starting at $2,395).

In its cleanest mode with the Rock/Jazz switch in the latter position, the Overdrive Supreme delivers crisp clean tones to the limit of its output stage. If you like to play clean at high volume, this amp does the trick. These tones sounded great with a Strat, though humbuckers also elicited a good degree of sparkle, as I discovered when playing it with a new PRS 12-string. The reverb is smooth and pleasing throughout most of its range, though the higher the setting, the more detached the effect seemed to become from the notes. I couldn’t obtain any sproingy surf textures either, even with the Reverb knob turned all the way up, but Fuchs probably intentionally voiced it for more “hall” and less “beach.” Interestingly, when the effects loop is set to Series mode with nothing connected to the Send and Return jacks, all you hear is output from the reverb tank. You either need to have a device in the loop for serial operation, or keep the switch in the Parallel position, which you’ll probably want to do anyway if you’re using a delay or a digital reverb.

Switching to the Overdrive mode, the Supreme delivers soaring lead tones that are ballsy and articulate. I had no trouble obtaining massive distortion from a Strat and a Tele, and even without kicking in the extra gain boost there was no shortage of creamy “forgiveness” in the dynamic response. Pegging the Gain knob is necessary for obtaining maximum grind from this amp, but the cool thing is, when you switch back to Clean mode the sound is dead clean. I didn’t notice any significant tonal difference between the Deep switch settings, but activating the Mid Boost fattens up the sound of single-coils quite effectively. The Overdrive Supreme has a strong midrange presence anyway, a quality that allows it to cut amazingly well in a loud band. (In fact, one tester reported being able to hear this amp clearly from the opposite side of a large stage, even when standing right in the blast zone of the other guitarist). The Overdrive Supremeis also louder and definitely more aggressive with the Rock/Jazz switch in the former position.

It’s very easy to get carried away with the sheer amount of distortion that’s available in Overdrive mode, however, by backing off on the Gain and Input knobs, it was possible to get killer medium-grind tones reminiscent of a cranked Fender Deluxe’s. This is a perfect mode for loud blues playing, especially with that output stage ready to leap into action like a cornered tiger when you dig in with your pick.

Supreme Court

There’s enough to like about the Overdrive Supreme that one can almost forgive its four-button Artist footswitch (an essential item that costs an additional $395; a standard 2-button switcher is no extra charge), which has a rather generic housing, label-machine stickers to ID its functions, and uses a fairly stiff type of high-tech cable with a multi-pin connector on the amp end — don’t count on an easy replacement if this baby fails in the field. (Fuchs states that the footswitch is being revised, and will have an aluminum bezel to replace the stick-on lettering.) A hip thing, however, is that its large LEDs are so intensely bright that you’d likely have no trouble seeing their indications even when playing at noon on the Bonneville Salt Flats.

The Overdrive Supremehas that rare quality of being able to draw you in immediately, yet continue to reward and inspire you the more you play it. Considering what it’s based on, it would be a surprise if the Overdrive Supreme wasn’t an impressive amp.

2:90 Power Amp — Drop-in Upgrade! — Universal Voltage Primary. Check availability before ordering — #561205

Low Power Tweed — 5C8 & 5D8 — smaller size — no CT on 6.3V winding

High Power Tweed — #7993 — slightly higher B+

High Power Tweed — #7993

Low Power Tweed Twin PT — 120V

High Power Tweed — 240V primary

100/100 — EL34 or 5881 Dual Monoblock power amp PT — Drop-in Upgrade!

Flat mount w/ lugs — 2 1/2″ x 3 1/8″ mounting centers

50 watt power — Plexi era through JMP MK.2 Master Volume models

#1202-164 — Vertical mount — Bolt hole spacing is 3″ x 3″

High Power Tweed Twin — true balanced center tap on 6.3V filament winding –Uses Grain-Oriented Iron

2:100 power amp — Drop-in Upgrade! — Universal Voltage Primary. Check availability before ordering — #561205

9005 50/50 — Rack mount power amp — #1204-314 — Upgrade!

Low Power Tweed Twin — smaller size — 230 & 240V primary

Low Power Tweed Twin — 220, 230 & 240V primary

Low Power Tweed Twin — With Universal Voltage Primary

I have a Mesa Triple Rectifier that for the most part I am pretty happy with, but I’ve read about replacing output transformers, tubes and all sorts of other stuff. I just want my amp to sound more present, punchy and for the distortion to sound clearer. What do you recommend?

The Dual and Triple Rectifiers are among the top five amp models we mod the most. You can check out the details, sound clips, etc on our website, however, before you go that route you may want to experiment with some new tubes and/or a new output transformer. For power tubes we really like the tone of the Ruby 6L6GCMSTRs with a PC rating number of around 35-45. For preamp tubes we have been using the GT-12AX-C (gold series) with our Standard or Deluxe Mods, but the GT-5751M (gold series) works well in a stock Mesa Rectifier.

The output transformer can also make a significant difference and recently we have been shipping our custom VAREC180-O output transformers directly to customers. These are made to our specs by Mercury Magnetics and it gives you 4, 8 and 16 ohm impedance taps. You can take the amp to your local tech to have it installed or perform the work yourself (if you know what you’re doing). The tonal difference is literally night and day. The amp will feel much easier to play on, tighter/richer on the bottom end, pinch harmonics come out with ease and the over all tone is much more focused

Partridge TG9685 — 120V, 220V, 230V & 240V primary — Partridge transformer design

2 amp 6.3V filament transformer with center tap

Wurlitzer 200 Electric Piano/Keyboard transformer. Replaces PN 11-0804 PT

Tapped transformer — for use with 5V or 6.3V tube rectifier — single 120V

8 amp filament transformer with CT

20 watt — Partridge transformer design

12 amp 6.3V filament transformer with center tap

Ten years after our first published amp review (the blackface Vibrolux Reverb), we still find ourselves answering readers’ questions about which amp to buy. We’re not complaining… your subscription to TQR has always included phone or email access for those contemplating a new gear purchase, but it seems that published reviews can still sometimes prompt more questions than answers. We understand, and like you, we are routinely faced with these same buying decisions just about every month as we look ahead to future issues. “Power” and “headroom” (or lack of it) seem to remain among the most daunting considerations for prospective amp buyers. This may not keep you up at night if you’re looking for a toneful box to play solely at home, but the range of clean and overdriven tones available from a single amplifier that can hang with a band is absolutely critical – the tipping point for guitarists who wish to have both clean and grittier tones available on the fly. And even the casual “bedroom” player (does anyone really play their guitars in the bedroom?) will quickly discover that big, lush guitar tones – clean or jacked into rich distortion – are often best obtained through a “bigger” amp. We’re not suggesting that we don’t love our ’58 tweed Tremolux or ’64 Deluxe – they both uniquely, timelessly epitomize great guitar tones – but an entirely different realm exists within the range of vintage Fender amps, and try as we might, we have never found another amplifier quite as versatile, user-friendly or uniquely toneful as the blackface (1965–7) 40 watt Pro Reverb – still the most under-valued and overlooked reverb amp from the entire blackface era, although aside from its 2×12 speaker configuration, the Pro is nearly identical to the Vibrolux and the Super Reverb amps.

Yes, the 2×12 Pro Reverb can move some air, just as an AC30or Matchless DC30, both highly coveted amps for good reason, do the same. Experienced in a room, 2×12 amps produce an ambient presence and a spatial quality that single 12s can’t match. That extra speaker isn’t adding volume as much as it simply disperse sound effectively by filling more space. And although the Pro Reverb is rated at 40 watts, the smaller output transformer Leo Fender chose to use delivers only 28 watts, probably in an effort to minimize speaker failure, yet the original Oxford and Jensen 12 s shipped in the Pro still blew when pushed by enthusiastic rockers. A well-maintained Pro Reverb will typically produce classically clean Fender tones with strong bass and treble and slightly diminished mids from “2” on the volume control to “5,” gradually spilling into lush Fendery distortion at higher settings. If you choose to use an overdrive device to achieve distortion at lower volume levels, the Pro will sound significantly better than most 20 watt amps because your pedal is affecting a cleaner signal, rather than adding distortion to an amp already spilling over into distortion. And as we have reported so often in the past, non-invasive and completely reversible modifications can be made, such as the addition of a 25K mid range pot utilizing the existing back panel hole for the extension speaker jack. This single mod enables the Pro to develop a very ballsy British voice as midrange is increased, while completely preserving the integrity of the original Fullerton tone with the midrange pot set at zero, rendering two outstanding amps in one. Intrigued? You should be, because we have never heard a contemporary boutique 2×12 combo amp that can approach the sound of a Pro Reverb equipped with a solid set of tubes and speakers. And with the range of speaker options available today, you can effectively custom design and shape the sound of your Pro for more of a traditional, bright“American” sound, a heavier or chimier British tone, or the two combined.

Ah, but buying old amps is risky business says you… what if I get a “dog” or it needs a lot of work? I’d rather buy some-thing new and not deal with the unknown. Fine, do that. But for those willing to reap the rewards that only a certain degree of risk can offer, it’s not that difficult to minimize your chances for disappointment. Here’s how:

View PDF Article

Today it seems as though there’s a boutique amp manufacturer around every corner. Don’t get me wrong — boutique amps aren’t a bad thing, but a great many of them focus on recreating the same types of tones that we’ve heard before, sapping all of the meaning from the word, “boutique.” If you were to be objective about it, you could make the argument that Leo Fender’s Bassman was the forefather of modern guitar amplification — it was the very amp that Jim Marshall and Randall Smith [Mesa Boogie] hot-rodded to make their own famous amps. But with so many small builders basing their sounds off these designs, where is the room for improvement?

With that said, I literally bumped into a mom and pop operation by the name of Industrial Amps at the Boston Guitar Festival, hosted by none other than Premier Guitar. I was wearing a Marshall T-shirt when I ran into JoAnn Niekrewicz, the co-owner of Industrial Amps; seeing my shirt’s logo, she shouted through the crowd, “Try our amps — they are Marshall killers!”

Needless to say, it was a bold statement, but curiosity got the best of me; I immediately sat down and tried all of their amps. Plugging into models like the Rock 120, Blues 60, Crunch 15 and the Overdrive 15, I soon noticed that each amp had its own special sound. The Blues 60 had a nice, hollow blues tone, while the Crunch 15 and the Overdrive 15 seemed perfect for studio recording, providing dynamic tone saturation. When I arrived at the Rock 120, I was thoroughly blown away by the depth of crunch that it produced, especially when it was played through the IA extended 4×12 speaker cabinet, loaded with Celestion Vintage 30s. To explore this amp further, I had them send the Rock 120 combo to my studio, so I could really put it through its paces in a working environment.

“The tubes, transformers and capacitors all cleverly reside behind 1/4″ thick glass, so you can experience the mesmerizing glow of electronics at work. As an added bonus, the Rock 120 is tour-ready, boasting a set of large, riveted, zinc-coated handles with grips on both sides of the case, as well as four caster wheels for easy transport.”

Industrial Rock

Right out of the box, the Rock 120 is a striking piece of modern, industrial design. The amp is constructed in a white Tolex case made from 3/4″ true 11- ply hardwood birch, with the speakers enclosed behind a heavy duty grill made from 1/4″ aluminum for kick-proof protection. As for the cabinet itself, Industrial Amps designer Tony Niekrewicz works closely with a non-profit organization called Living Classrooms in Baltimore, MD. The program gives out-of-school youth, from ages 16-19, a chance to learn carpentry hands-on in a practical work environment.

The tubes, transformers and capacitors all cleverly reside behind 1/4″ thick glass, so you can experience the mesmerizing glow of electronics at work. As an added bonus, the Rock 120 is tour-ready, boasting a set of large, riveted, zinc-coated handles with grips on both sides of the case, as well as four caster wheels for easy transport. Electronically, the amp features 120 watts, two channels — Classic and Heavy — point-to-point hand wiring and an open back cabinet fitted with two 12″ Celestion 80s. The amp itself is powered by four premium 12AX7s, four EL34s, one 12AT7 for reverb and a solid state rectifier tube.

Turning my attention first to the Classic channel, I ran several guitars through it. In particular, my Gibson double-neck Jimmy Page Model produced a gorgeous, ringing tone, much like the tone you hear on the Birds song, “8 Miles High” or even the Zeppelin classic, “The Song Remains the Same.” A word of advice: when using double humbuckers, you’ll have to back off on the guitar’s volume a bit so you won’t overdrive the amp. What worked best for me was a Fender Strat. Though the Classic channel, the single coils produced a very smooth and fresh reverberation, similar to that of a Fender Deluxe.

Switching over to the Heavy channel produced a genuinely heavy bass response, perfect for shaking your tree. Overdriven, the Rock 120 is a cross between a classic Mesa Boogie Mark II and a Soldano amp. I used the amp on several recording sessions and even had Leslie West [of Mountain] play through the amp. He was very impressed with the amp’s gain — this coming from a guy that can never have too much gain. The notes were expressive and had an authentic, singing overtone; for those of you who remember the short-lived Fender Prosonic amp, this amp has a similar, driving tone.

The Rock 120 also recorded very well, especially using a Les Paul Goldtop with a Seymour Duncan ’59 humbucker in the bridge position and a Duncan Custom in the neck position. The tones were very saturated, but without the muddiness that some overdriven amps generate, due to theMercury Magnetics transformer inside — designed to provide both clarity and bottom growl. It has that Mesa Boogie singing tone and is great with pinch harmonics. The Treble, Bass and Presence controls are quite responsive, and unlike some amps, each one of the knobs really affects the tone. As an added bonus, the Heavy channel features a Gain control and a Master, so you don’t have to sacrifice your eardrums for sweet tone.

There’s lots to love here, but IA has thought to add in plenty of little touches that will make the purchasing decision easy. Each amp features dual speaker outs, voltage and ohm selectors, military spec components, and even, “severe duty Honeywell explosion-proof aircraft quality switches.” How much more rock n’ roll can you get?

The Final Mojo

Being an avid collector of vintage tube amps, I’m always skeptical of new products claiming to have superior sound. But my experience with Industrial Amps opened my ears to what small amp builders can achieve. While the price may be equivalent to other boutique amp models out there, the Rock 120 definitely gives you a lot more, in terms of sound and power. You won’t find this amp in Guitar Center, Sam Ash or any of the others commercial retailers — this a true underground find.

Source: https://mercurymagnetics.com/pages/news/PremierGuitar/PremierG-09.htm

Quietly, outside of Los Angeles, Steve Trovato has been leaving blazing guitar everywhere he goes.

Currently, he is a full time instructor in the Studio Jazz Department at the University of Southern California. In addition, Steve has found the time to author over 20 instructional books for Warner Brothers and Hal Leonard, produce over 50 instructional videos for the likes of Yngwie Malmsteen and Paul Gilbert, and has even starred in five of them. His students have achieved major success and include Scott Henderson, Frank Gambale, Paul Gilbert and Norman Brown. He has performed with Chet Atkins, Albert Lee, Robben Ford, Jeff Berlin, Jerry Donahue and Scott Henderson, and contributes to five international music publications, including Guitar Player, Guitar One, Axe, Guitar Club, Guitar World and Chittar, as well as recording for too many studio and motion picture projects to list. We caught up with Steve as he completed his new release, Country Jazzmaster.

One of the things I have always wondered about is who or what influenced you to start playing guitar?

Well, I think you’ll hear this from a lot of guys; it was the Beatles. I think I was six years old, and I had been playing the piano. I did my piano recital and played “The Blue Danube Waltz.” Then I saw the Beatles on Ed Sullivan and I thought, “Wow, girls never screamed for me playing piano.” So that was it and I started playing the guitar. That was pretty much it, and I have never looked back.

Did you come across a single moment that it finally hit you? This is it, this is what I want to do the rest of my life?

I’ve never been asked that before; that’s a really good question. I would say that there were three pivotal moments: one of them was when I saw the Beatles, the second was when I heard Chet Atkins for the first time, and the third was when I was up on stage and I got a chance to play with Albert Lee — that was when I really knew I wanted to do guitar. For some reason those guys hit me hard — they played melodies — and I always loved the way I could track it even though it was guitar playing. It was really very sophisticated. When I heard Chet Atkins play, I could hear the melody. Even with all the notes that Albert Lee plays, I can still keep track of it– that’s what attracted me. I think since I’ve been playing, if I have anything, it’s the ability to play a melody.

You’re originally from New Jersey. How did you end up on the West coast attending GIT (now the Musicians Institute)?

Like every guitar player on the East Coast, we were always hungry for information about the guitar. I used to get this magazine and I saw an ad for this place called GIT in California. I saw pictures of Larry Carlton, Tommy Tedesco and other people that I didn’t know, like Don Mock and Joe Diorio, and they were starting this school. They were sort of advertising it being for studio musicians, and that was what I wanted to be.

Now that you already have one CD under your belt, you’ve gone into the studio a second time with some outside input. How are you achieving your tones with the studio?

When I did my first album, I just took my rig into the studio with the thought that if it sounds good live, it will sound good in the studio. I’ve found that not to be true. I also realized that amps that are made specifically for recording don’t necessarily sound all that good in the studio. It really depends on the studio, the mics, and everything else. I brought every amp that I had down there — I even borrowed some amps. I ended up with five or six different amps and I had to just go through all of them to find out which one sounded the best in that studio — with that particular set up of room and microphones. I wound up actually using a boutique amp from a company in Virginia called Talos. I love those amps. It’s a 60-watt, one-twelve, and it just has two knobs on it, drive and gain.

“Well, I think you’ll hear this from a lot of guys; it was the Beatles. I think I was six years old, and I had been playing the piano. I did my piano recital and played ‘The Blue Danube Waltz.’ Then I saw the Beatles on Ed Sullivan and I thought, Wow, girls never screamed for me playing piano. So that was it and I started playing the guitar. That was pretty much it, and I have never looked back.”

What about guitars? Did you find that’s the same scenario to be true?

It’s something I suspected, but I never really had the chance to put it to the test. I usually use my G&L Legacy live, with the Kahler on it because it sounds great. You’re playing loud enough where if there’s a bass, drums and everything cranking you lose the nuances and the subtlety. But in the studio you retain those nuances and subtleties because everything is under a microscope. I found that using different guitars expresses that better.

If I want to play a sensitive, sort of Chet Atkins jazzy piece, the Legacy wouldn’t work because it sounds too thin, but with a loud phrase it will sound fine. For a quiet passage, I decided to use a Gibson — a Howard Roberts with two old humbuckers that I had. Of course, for the Straty-sounding things I used my red Legacy with a Kahler on it, which I absolutely love. For the rest of the stuff I used one of two Teles: a Fender solid body Telecaster and a G&L semi-hollow. None of them are stock. Seymour Duncan custom built the pickups for both of them.

What amps do you prefer for live performances?

I play rock, I use my Dumble. That, of course, is Alexander Dumble. It says “Built to win” and it really does, it’s just really something. I put a pedal in front of it to make sure it’s got enough overdrive. In the country bands I use a ’65 Pro Reverb, which Dumble rebuilt for me.

What do you use on the jazz side?

I use my Talos.

Throughout your time as a guitar player, you’ve been labeled as the chameleon of guitar. Do have a huge arsenal of guitars at your disposal that you have hiding in the back room to take out whenever you need to?

For the live work I pretty much grab whatever is nearest to the front door on the way out. I was never really one to take ten guitars to a session because I figured that one guitar would sound just as good as 10 guitars, but when you really start to do this seriously, there are subtle differences between all guitars that may or may not sound better for the tracks. You really have to have an arsenal of quite a few to do the job right.

What would be an ideal arsenal?

I would have to say you have to have a solid body, Strat-type of guitar with single coil pickups, a single coil Tele-type, a Les Paul-type solid body with humbuckers, a thin semi-hollow body sound, like a 345, and a jazz box, then, of course, steel string acoustic and a nylon string.

You mentioned putting a pedal on the floor in front of one of the amps.

Live I use a Boss GT-6. I use it for time delay effects such as reverbs, delays and chorusing. It sounds great for that and it’s also great on the floor. For distortion I’ve been using the AC Booster and the RC Booster by Xotic Pedals.

The Xotic pedals are fairly new. Can you tell us some more?

Oh, I love them. Those are the kind of the boutique pedals that all the guys in town are using. Scott Henderson told me about them. Studio guys like Michael Thompson are using them. Basically, the RC Booster is a pre-amp boost that keeps it clear, but gives it a little oomph. The AC Booster is an overdrive — basically a really high-end Tube Screamer with a bass control on it. Everybody loves Tube Screamers, but it takes the bass away from it; this is a Tube Screamer that sounds a lot more transparent and smoother than normal. You can also roll the bass back in because it has bass and treble controls.

You mentioned the Kahler Tremolo on one of your G&L’s. What do you like about it?

The thing I love about the Kahler is its flush and mounted solidly on the guitar body, versus another one. I won’t mention any names, but the initials are Floyd Rose. It is not really mounted on the body of the guitar as solidly and or as flush as a Kahler. With a Kahler, the tone sounds pretty darned good. I really like that about the Kahler. Since you have that big plate to rest against the body, you get more natural wood resonance, it doesn’t sound thin and small. The other thing that I like is the adjustable string spacing. I don’t think other bridges can do that.

On the first CD, About Time, you cover a whole spectrum of guitar playing. You do a dedication to Danny Gatton, you’re hitting a little Django, you’ve got “Somewhere Over the Rainbow” from Harold Arlen, and then you even do Billy Joel’s “Root Beer Rag.” What can we expect hear on the new CD?

When I spoke with Steve Vai, he was saying the last CD was really good but I needed a little bit better recording quality. He said the problem with the first CD, as far as marketing, is that I don’t know where to market it stylistically; it’s all over the map. I came up with this concept in my mind called “Country Jazzmaster,” with Jazzmaster being one word, like the guitar. I kept that thread in my mind as I was recording this album, and all of the songs leaned into that concept. Everything that you’re going to hear is country-jazz. Western swing, country jazz — that sort of a thing.

There’s a thread of continuity running through the whole album that you will hear. I recorded everything from the old Jerry Reed tune, “Guitar Man,” to “Back Home Again in Indiana,” “That She Could Ever Be,” “Panhandle Rag” and my ultimate version of “Ghost Riders in the Sky.”

I still remember this vivdly: a NAMM show where you, Steve Vai and I were standing around talking, and Steve hailed you as, “One of the greatest Tele players of all time.” Will we hear evidence of this on the new CD?

That was very nice of him. But, yeah, that’s what I’m hoping for, and I think that it’s really extremely well played, if I can say so myself. We all worked really hard on it.

Trovato Gearbox: Here’s what Steve is plugging in, when it’s time to shine.

Country Gigs

Guitars

• G&L ASAT Tele stock
• G&L ASAT semi hollow body w/Seymour Duncan P90’s

Amps

• Groove Tubes Trio Pre amp
• Groove Tubes 75-watt power amp
• Groove Tubes 2×12 cabinet w/Celestions

Effects

• Boss GT-6
• Keeley Compressor
• Xotic RC Booster
• Xotic AC booster

Rock/Blues Gigs

Guitars

• G&L Fullerton Red Legacy with Kahler and custom Seymour Duncans
• ‘69 Fender Strat (stock)

Amps

• Early ’80s Dumble Overdrive Special
• Two 1×12 Dumble cabinets with Mojo Tone Speakers
• ’65 Fender Pro Reverb with Mercury Magnetics Bassman replacement transformer and 2×12 Mojo Tone Speakers modified by Dumble

Effects

• Boss GT-6
• Maxon Tube Screamer
• Fulltone OCD pedal
• Zendrive Pedal

Steve Trovato: It’s About Time and the new, Country Jazzmaster, are available at: cdbaby.com / myspace.com/stevetrovatomusic

Source: https://mercurymagnetics.com/pages/news/PremierGuitar/PremierG-07.htm

Reverb-O-Jet — J-12-R

V3212 — Drop-in Upgrade!

Blackface — no 5V winding — solid state rectifier — Fender #125P7D

Blonde — 6G6B circuit — Fender #125P7D  (022814)

338 – 0 – 338 volts — flat mount, bolt hole spacing is 2 3/4″ x 3 7/16″

Blackface — 5V winding — #125P5D export — Universal Voltage Primary

Blonde — #125P7D — 100V, 120V, 220V, 230V & 240V primary

Tweed — 50V bias tap — lower B+ — 325-0-325

Blackface — lowest B+ — 250-0-250

Tweed — lowest B+ — 250-0-250

Blackface Reverb — Universal Voltage Primary

Silverface Bassman 100 — #125P34A / 022756 — Upgrade! Please confirm mounting centers before ordering.

Super Six — Drop-in Upgrade!

Upgrade!

Blackface — Lower B+ — 325-0-325

Great for use with single 6L6, 5881, KT66 or EL34 tubes

Blackface — 50V bias tap — 360-0-360 unloaded B+ — Universal Voltage Primary

Fatstack — 2 1/2″ lamination stack — ok to use with two 6L6 — hole spacing 2″ x 2 1/2″

Blackface — #125P5D

Blackface era — #125P5D — mounting holes 2 3/4″ x 3 7/16″

Brown 2 x 10

Blackface — #125P5D-X — Universal Voltage Primary

Blackface — Universal Voltage Primary

Tweed — Model 5E5-A — with bias tap

Brown — #68249

Mid ’50s Tweed – 5E4-A — two 6V6 tube version — lower B+ — 335-0-335

Tweed — Model 5E5-A — with bias tap — 220V, 230V & 240V primary

Silverface Bassman 100 — 220V, 230V & 240V primary taps — Upgrade! Please confirm mounting centers before ordering.

Upgrade for ’65 & ’68 Reissue Deluxe Reverb — bolt hole spacing is 2 1/2″ x 3 1/8″ — 2″ stack

Brown — 220V, 230V & 240V primary

Drop-in Upgrade for Export Reissue Deluxe Reverb– 220V, 230V & 240V primary

Upgrade for ’65 & ’68 Reissue Deluxe Reverb with lower B+ — bolt hole spacing is 2 1/2″ x 3 1/8″ — 2″ stack

Brown reissue — use with solid state rectifier — Upgrade!

Brown reissue — use with solid state rectifier — single 240V — Upgrade!

Brown — #67233 — 6G7 version

Upgrade!

Lightning — Drop-In Upgrade!

Lightning — Drop-In Upgrade!

’80s Bassman 20 — #19118 — Upgrade!

’80s Bassman 20 — 220V, 230V & 240V primary taps — Upgrade!

135 watt version — #013692

’70s — 135 watt — #013692

Rickenbacker M8 — single 120V primary tap

Supro Spectator — Drop-in Upgrade!

Supro Super

GA-19RVT — Please confirm mounting style before ordering

Blackface — Universal Voltage Primary

Blackface — 220V, 230V & 240V primary

Blackface — 220V, 230V & 240V primary — #125P1B

Blackface Vibro — 220V, 230V & 240V primary taps

Blackface — single 100V primary tap

Galaxie 25 — Upgrade! — 288-0-288 unloaded — Larger size

Blackface Vibroverb Custom — single 120V primary — Drop-In Upgrade!

Tweed — 5D4 — no CT on 6.3V

Blackface Vibroverb Custom — Universal Voltage Primary — Drop-In Upgrade!

Tweed — 5D4 — no CT on 6.3V — 220V, 230V & 240V primary

“Custom” — ’95-’96 Blackface — #037610 — Upgrade!

‘”Custom” — 95-’96 Blackface — 220V, 230V & 240V primary — #049181 — Upgrade!

GA-6 — Drop-in Upgrade! Please confirm mounting style before ordering

GA-35 RVT — Drop-in Upgrade! Please confirm mounting style before ordering

GA-23 — Please confirm mounting style before ordering

350-0-350VAC unloaded B+ — Center Tapped 6.3V — 5V Rectifier Winding — Styles vary: please confirm mounting style before ordering

GA-15 –Original PT # TF 105 P

Flat mount — bolt hole spacing is 2″ x 2 1/2″

Wards Airline GIM 9131A — circa ’60s — single 120V primary tap

4100 — Drop-in Upgrade!

30th Anniversary 6100 — Drop-in Upgrade!

Excelsior — Drop-in Upgrade!

TSL60 — 3H — 250mA — add this choke to your TSL60 for improved tonal richness

100 Watt JCM2000 — Dagnall D2105 (TXMA 00061)- SuperStack (over 4″ of Iron!)

** 5 1/2″ tall, for head amp cabinets only (no combos) — Bolt hole spacing is 2 1/2″ x 3 1/8″

TSL60 — Upgrade!

F50 — Drop-in Upgrade! 120V Primary — #561054

Vertical stand up type with 2 1/2″ x 2 3/4″ mounting centers

Road King II — 120V usage — FatStack Upgrade!

Maverick — single 120V primary — Drop-in Upgrade!

Maverick — Drop-in Upgrade! — Universal Voltage Primary

Subway Rocket & Subway Blues amps — #561122 — 100V & 120V usage

Horizontal mount, bolt hole spacing is 2 1/2″ x 2 3/4″

Rocket — 110V & 120V usage — Drop-in Upgrade!

DC-3 — 100V & 120V usage — Drop-in Upgrade!

Rocket 440 — 110V & 120V usage — Drop-in Upgrade!

MESA Part Number #561160 — 120V usage — FatStack Upgrade!

50 Watt Combo — Drop-in Upgrade! — single 120V tap

50 Watt Combo — Drop-in Upgrade! — Universal Voltage Primary

Thunder 30 — Drop-in Upgrade! — Universal Voltage Primary

Dark Terror – Single 120V primary — Drop-in Upgrade!

JTM45 — Drop-in Upgrade!

DC30 — Drop-in Upgrade!

Delta Blues — FatStack Upgrade!

Delta Blues — FatStack Upgrade! — Universal Voltage Primary

Epiphone Comet PT Single 120V primary

Sears Silvertone — Model 1471

’70s 100S

Mr. Tone Controls — #0067194000

SVT II Preamp — Drop-in Upgrade!

115V primary — secondary has 120V @ 45mA winding and dual 12V windings @ 0.2A each

Foot pedal

Foot pedal — 220V, 230V & 240V primary

ADA MP1 preamp — single 120V primary — Upgrade!

Echoplex Delay/Echo Unit — Solid State version — circa ’60s-’70s — 120V. To guarantee compatibility, please contact us before ordering.

Reverb unit — Single 120V primary

Sears Silvertone — Model 1481

Wem Copy Cat

Blackstar HT1 — Drop-in Upgrade! –120V Primary

Mercury — 120V

Sears Silvertone — PT for models 1457 and 1449

Echoplex Delay/Echo Unit — tube version — circa ’60s-’70s — 120V. To guarantee compatibility, please contact us before ordering.

Altec / Peerless — #6216

Reverb unit — Universal Voltage Primary

Class 5 — Universal Voltage Primary — more iron! — Drop-in Upgrade! — #TXMA-00131

Interstellar Overdrive — M-TAP — #0067187000

Kalamazoo Model Two — #TF 102P

Sears Silvertone — Model 1481 single 240V Primary

Rickenbacker M9 — single 120V primary tap

Blackstar HT5 — Drop-in Upgrade! — Universal Voltage Primary

Echoplex Delay/Echo Unit — tube version — circa ’60s-’70s — 220V, 230V & 240V primary. To guarantee compatibility, please contact us before ordering.

L5 — Drop-in Upgrade!

240V, 230V & 240V primary taps

Yamaha CS20M Analog Synthesizer Keyboard– Upgrade!

Preamp / Processor — Drop-in Upgrade! 110V, 120V, 230V & 240V primary

’70 upgraded Drop-in Upgrade! with an extra 1/4″ of iron — #026821

Reverb unit — 120V & 125V primary — no center tap on B+ winding — 288V unloaded — CT on 6.3V @ 4A

GA-5 Les Paul Jr. — Please confirm mounting style before ordering

GA-5 Skylark — 5V winding 240V primary — Please confirm mounting style before ordering

’55 Tweed — #7787 — flat mount, bolt hole spacing is 2″ x 2 1/2″

1″ tall lamination stack

’55 Tweed — 240V primary

GA-5T (Skylark) — no 5V winding — 120V primary — #TF-5A-P

Flat mount — bolt hole spacing is 2″ x 2 1/2″

GA-5 — 5V winding. Please confirm mounting style before ordering

GA-5 Skylark Crestline — no 5V winding — no CT on 6.3V filament winding — 120V primary

#TF-5A-P — Flat mount — bolt hole spacing is 2″ x 2 1/2″

GA-5 Skylark — 5V winding. Please confirm mounting style before ordering

Custom 7 — Drop-in Upgrade! — Universal Voltage Primary

Model 147 or 122 — reverb amp

Workingman 10 / LA12 — #0067228000 — 100V / 120V

Workingman 10 / LA12 — #0067222000 — 220V

Quad-Preamp — Drop-in Upgrade! — Universal Voltage Primary — Uses Grain-Oriented Iron

Classic 20 — #705-28733 — FatStack Upgrade, 1 7/16″ tall lamination stack

Flat mount — bolt hole spacing is 1 3/4″ x 2 3/16″

Classic 20 — 220V, 230V & 240V primary — FatStack Upgrade!

Blackface — Low B+ — 250-0-250

Binson Echorette — circa ’60s — multiple primary taps

Early ’60s Brown — #125P1A

59 Tweed — 330-0-330 — NO CT on the 6.3V winding — 5V winding

EH-125 — late ’30s & ’40s — Please confirm mounting style before ordering

Sears Silvertone — Model 1333

Blackface Champ — #125P1B — Flat mount 2″ x 2 1/2″ hole spacing

Blackface — #125P1B — stock size, uses 1″ lamination with 1 1/4″ tall stack

Silverface amps had same PT, but marked as #022772 (early) or #L010020 (later)

Mounting hole spacing is 2″ x 2 1/2″ — ** Also works in Fender’s reissue ’65 Princeton Reverb amp

Blackface Vibro Champ — #125P1B — Flat mount 2″ x 2 1/2″ hole spacing

120V — Upgrade!

Tweed — 220V, 230V & 240V primary

’60 Tweed — #66079, #125P1B — flat mount type, 1 1/4″ tall lamination stack

Bolt hole spacing 2″ x 2 1/2″

’60 Tweed — Single 100V primary — higher B+

Tweed — #125P6A

Late ’50s Tweed

GA20-RVT — Original PT # TF 105 P

Flat mount, bolt hole spacing is 2″ x 2 1/2″

GA-5 — no 5V winding — 220V, 230V & 240V primary — Please confirm mounting style before ordering

GA17 — Original PT # TF 105 P

Flat mount, bolt hole spacing is 2″ x 2 1/2″

Goldtone GA15 reissue — Drop-in Upgrade! Please confirm mounting style before ordering

Range Master — Single 120V primary — Drop-in Upgrade!

’60s — #80-5048-6 — hole spacing 2″ x 2 1/4″

*Fits the Berkeley tube amp head also

V5 — Single ended 120 volt primary –Upgrade!

Galaxie 25 — Upgrade! — 335-0-335 unloaded — with bias tap — larger size — dual primary 120V, 230/240V primary

Valve Special — Upgrade!

single 120V primary — Upgrade!

Super Champ X2 — 120V primary — Drop-in Upgrade!

’59 Tweed — 220V, 230V & 240V primary

Slash 5 — Drop-in Upgrade! –Universal Voltage Primary

Valve King Royal 8– Upgrade!

Upgrade!

Old Workingman 12 — #0067195000 — 100V

LA15 / Old Workingman 12 — #0067188000 — 120V

LA15 / Old Workingman 12 — #0067189000 — 220V

LA15 / Old Workingman 12 — #0067190000 — 240V

Early ’90s Champ 12 — Drop-in Upgrade!

Early ’90s Champ 12 — Universal Voltage Primary

Jet — #PT-105

Early ’60s

Studio 15 — Upgrade! — Drake 294-285/5

’80s Super Champ — #019118

Hughes & Kettner Tubemeister 18 — Universal Voltage Primary

Tweed — 100V & 120V primary

Mid ’50s Tweed — 260-0-260 — CT on the 6.3V winding — 5V winding

Late ’50s Tweed — Universal Voltage Primary

Studio Caliber 22 & Studio 22+ — #561022 — Drop-in Upgrade! — Universal Voltage Primary

’60s used with two 6BQ5 tubes — unloaded B+ 350-0-350 — 6.3V CT

Sears Silvertone — Model 1482 — #P14

Flat mount, bolt hole spacing is 2″ x 2 1/2″

Sears Silvertone — Model 1482 — 220V, 230V & 240V primary

’60s Brown — 220V, 230V & 240V primary

’80s Deluxe Reverb II

’80s Super Champ — 220V, 230V & 240V primary

Tweed — 370-0-370 High voltage winding. Staggered gap, tuned core — #6452

GA-45RVT — Please confirm mounting style before ordering

GA-5 — 5V winding — no CT on 6.3V winding — 220V, 230V & 240V primary taps — Please confirm mounting style before ordering

Reverb-Tremolo

JTM 30 watt

Early ’90s Champ 25 — #A-039043 — Drop-in Upgrade!

80s Deluxe Reverb II — 220V, 230V & 240V primary

Tweed (very early!) — special design — #6452

Tweed — stock B+ — 380-0-380 unloaded — #6452, amp models 5C3 to 5E3

Tweed — lowest B+ — 290-0-290 unloaded

Tweed — lower B+ — 335-0-335 unloaded

Universal Voltage Primary — Drop-in Upgrade!

’60s — solid state rectifier — 220V & 240V primary — lower B+ voltage

’60s — solid state rectifier — 120V primary — lower B+ voltage

Artist 30 3203 Head & 4203 Combo — Drake — #1961-112 / 7

Class 5 — Universal Voltage Primary — Upgrade!

Rectifier Recording Preamp — Drop-in Upgrade! — Universal Voltage Primary

Baby Blue — #0067175000 — 100V

SVT II — Upgrade!

Tweed — lower B+ — 350-0-350 unloaded

Tweed — 388-0-388 High voltage winding. Staggered gap, tuned core — #6452

Tweed — medium-low B+ — 313-0-313 unloaded

Early ’70s Specialist — 120V primary — Upgrade! — DE# T 3133

Classic 30 — 1 1/2″ thick lamination FatStack Upgrade! — Single 120V Primary

#705-28739 — flat mount, bolt hole spacing is 2″ x 2 1/2″

Pignose G40V — 40 watt — Upgrade!

’60s Westminster — Euro primary taps

Baby Blue — #0067176000 — 120V

Jet — lower B+ — #PT-105

Tweed — 220V, 230V & 240V primary

Tweed — Dual B windings: 260-0-260 and 310-0-310VAC — Single 120V primary — Not Available in Flat mount

B80N — ’70s solid state

Dominator

Scout Original

#5201 — Circa 1950s

Blackface — lower B+ — 220V, 230V & 240V primary

1946 era Woodie/Woody Deluxe — vertical mount — #5568

Tweed — Universal Voltage Primary — lower B+

Tweed — Universal Voltage Primary

Jet City PicoValve — Drop-in Upgrade! — Universal Voltage Primary

Upgrade! — # TXMA – 00081

F30 — #561122 — 100V & 120V usage

Horizontal mount, bolt hole spacing is 2 1/2″ x 2 3/4″

F30 — Drop-in Upgrade! — Universal Voltage Primary

’70s — RD50 — Higher B+ 0-321V — Upgrade!

1946 era Woodie/Woody Deluxe — vertical mount — single 240V primary tap — #5568

single 120V primary –Upgrade!

GA-20. Please confirm mounting style before ordering

BX100 — Drop-in Upgrade!

Vintage 16 — Drop-in Upgrade!

Brown — early ’60s — lower B+ — #125P17A

Upgrade! — Universal Voltage Primary

Jet City 20 watt — Drop-in Upgrade! — FatStack with Universal Voltage Primary

213 — early ’60s — #6206 — Vertical mount, bolt spacing is 2 1/4″ x 2 1/2″

Reverb-O-Rocket — 5V winding — #PT-106 — 682-143

Flat mount — bolt hole spacing is 2 1/4″ x 2 13/16″

Brown — early ’60s — #125P17A

Blackface Reverb — lower B+ — 315-0-315 VAC

Blackface Reverb — lower B+ — 290-0-290 VAC

Blackface — 50V bias tap — lower B+ — 325-0-325

Mounting hole spacing is 2″ x 2 1/2″ — 1 7/8″ lamination stack, taller than stock

Blackface — 50V bias tap added — 360-0-360 unloaded B+

Has taller 1 7/8″ lamination stack — mounting hole spacing is 2″ x 2 1/2″

Blackface — 50V bias tap — 360-0-360 unloaded B+ — Universal Voltage Primary

Troubadour — late ’50s

’60s Wem Dominator III

Blackface — #125P23C — 1 1/2″ stack — Low Flux Density version of FBFDR-P

*Same 350-0-350 VAC as FBFDR-P — bolt hole spacing is 2 1/4″ x 2 13/16″

Blackface Reverb — #125P23C — Orig size 1 1/2″ stack — 350-0-350 VAC

Flat mount, bolt hole spacing is 2 1/4″ x 2 13/16″

Blackface Reverb — Universal Voltage Primary — Lower B+ — 340-0-340 unloaded

Tweed — 100V & 120V primary

Tweed — 100V & 120V primary — Lower B+ — 335-0-335 unloaded

Tweed — lower B+ — 350-0-350 unloaded — Universal Voltage Primary

Tweed — lowest B+ — 290-0-290 unloaded — 220V, 230V & 240V primary taps

GA-8T — Please confirm mounting style before ordering

Early ’70s Specialist — 220V, 230V & 240V primary — Upgrade!

Classic 30  — FatStack Upgrade! — Universal Voltage Primary

Supro Tremoverb Lower B+ version

Blackface Reverb — 230V single primary

Drop-in Upgrade! with a 2″ FatStack or iron! Dual B+ taps. Extra B+ tap is great for two 6L6 tubes.

Drop-in Upgrade! with a 2″ FatStack or iron! Dual B+ taps. Extra B+ tap is great for two 6L6 tubes — 220V, 230V & 240V primary

GA-20-T — 120V, 220V, 230V & 240V primary — ’60s. Please confirm mounting style before ordering

Nomad 45 — 100V & 120V primary — Mesa #561134

Also for Mesa Boogie Rocket 44

’60s Supro — model 1624T

Supro Tremoverb

Leads with short stack

Valve Standard — Upgrade!

60s — solid state rectifier — 100V, 120V, 220V, 230V & 240V primary

DE #T 2650

Custom Classic (Early version) — Drop-in Upgrade for Small Version: Mounting Centers: 2″ X 2-1/2″ — Single 120V Primary — Correct for the AC15 C1 amp

’70s — 135 watt — 220V, 230V, 240V primary — #013830

GA-40T — TF 60P — Please confirm mounting style before ordering

AD15 – Drop-in Upgrade!

Pignose G40V — 40 watt — Upgrade! — Universal Voltage Primary

Single 120V primary — Drop-in Upgrade!

Pro Jr — Universal Voltage Primary — Upgrade!

Custom designed — 25 watt

Custom designed — 25 watt — 220-0-220 unloaded B+

Sears Silvertone — Model 1484 — #DD-50

Vertical mount, bolt hole spacing is 2 1/2″ x 2 1/4″

Tweed — lowest B+ — 290-0-290 unloaded — 100V, 120V, 220V, 230V & 240V primary taps

Blackface Reverb — 1 3/4″ stack — #025130

Tweed — FatStack — 100V, 120V, 220V, 230V & 240V primary — stock 380-0-380 unloaded B+

Tweed — lowest B+ — 330-0-330 unloaded — Universal Voltage Primary

Tweed — lowest B+ — 280-0-280 unloaded — vertical mount only — separate 64 volt bias winding

Modern 40 watt

#5201 — Circa 1950s — Universal Voltage Primary Version

Jet — #PT-105 — use this PT with current production 7591 style tubes

Reverb-O-Rocket — 5V winding — #106 — Universal Voltage Primary

Blackface — Universal Voltage Primary — #125P23CX