November 01, 2009 | Paul Zoskey of

Mercury Magnetics Epiphone Valve Jr. Upgrade Kit Build

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.


Epiphone Value JR Modification Part 1 from GitFix on Vimeo.

Epiphone Value JR Modification Part 2 from GitFix on Vimeo.

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.

So with that I purchased two Epiphone Valve Jr. heads and requested a kit from Mercury so we could modify the amp and then see how it stacked up against a stock unit. Phil Manley was the perfect guy to take on this project for GuitarFixation. Phil has a wealth of experience with electronics from building his own fuzz pedals to repairing amplifiers. Phil also has a well-stocked workbench in his garage (yes, a garage in San Francisco -- there will never be a time that I donít covet his garage) that includes a quality soldering iron with adjustable heat and a large assortment of tools, parts, and meters. Again, this is really a project for an intermediate; I would not recommend this to someone who is picking up a soldering iron for the first time.

With all of the parts together I headed over to Phil's on a foggy San Francisco morning and we began the modification. Pulling the amplifier apart and removing the components was a simple enough task, as Mercury includes a disk with the kit that contains a huge manual and some videos. The only real issue with the instruction manual was that it had almost too much information. The manual is for all three versions of the head (current production is version three) and that made them a little hard to read because the document was referencing all the versions on one diagram. That being said, the instructions are very thorough and it is a good idea for you to read them a few times before you start. [Editorís Note: Always RTFM, boys!]

Discharging the caps on the main board is a fairly simple task; you just want to ensure that they are totally drained as to avoid any chance of a shock. We didn't plug in the amp before we started the modification so there was no juice to be found, but if you are going to use the old screw driver technique, you should remember to ground it. A good way to do this is by getting two alligator clips with a wire in between them and connecting one side to the screw driver and the other to a grounded source. It reminded me of when I use to work on tube television: one had to discharge the picture tube with a flat blade screwdriver -- POP!

An indispensable tool for this kind of work is a solder sucker that is used to remove hot solder from a board or component. You simply heat the area till it flows and then you load the solder sucker by compressing the spring. Then simply put it over the area in question and hit the button. This will remove most of the solder from the area (you may have to do it twice to get it all), well worth it, as makes adding the new components much easier. You can get one from Radio Shack, but beware their tiny under-$10 model. Be sure to get a half decent one that has a lot of suction to clear away the solder. I recommend the "Edsyn Solder Sucker" it is the one Phil is using in the video. You can get an Edsyn from MarkerTek for about $24 -- you can get it HERE.

A Dremel tool will also serve you very well for the modification of the amp. I ended up buying one after Phil had already completed all of the trace cuts on the board (sorry Phil!) The Dremel would have made these cuts worlds easier when compared to using a flat head to scrape away at the trace. If you are not going to use a Dremel then you will want to double check the trace cuts with a meter set to continuity and to ensure that the cuts are 100% or youíre in for some trouble down the road. You will also need a step bit if you decide to do the 6V6 mod, but you could always use a drill and Dremel like we ended up doing when the local hardware store came up flat in the step bit selection (see the video).

So to this point Phil had been working on the amp for a total of five hours, but we had taken a few minutes for lunch and had to make a trip to the hardware store. So in reality I would say this first section took Phil roughly two and a half hours. If you were working alone without someone pointing a camera in your face I think you could have it done in less than two hours. So far the kit is straightforward and easy enough to work on with a reasonably clear set of directions to work from (but be sure to print them in color!) The fun will continue in part two as Phil really gets into the nitty-gritty of this amp mod.

Now on to the installation of the installation of the transformers and Mini-Choke. You want to pay close attention to the directions in terms of how to twist and dress the wires in the chassis. The way you dress your wiring can mean the difference between an amp that is a quiet monster and one that is not even usable. You would not believe the difference a clean, tight wiring job makes on a tube amp!

The re-soldering of the components to the main PCB (printed circuit board) is a fairly simple task, there is not too much that you need to be on the look out for. I had mentioned in part one that you will want an iron that has a variable temperature control; this really comes in handy when you are soldering the resistors and caps. You donít want to overheat these components as you may damage them and degrade their performance. A high-quality iron is one of the most important tools for this kind of work; it will make all the difference in the world in terms of ease of use and component damage. I also recommend that you look at getting some high quality solder. I use Cardas Quad Eutectic Solder and it is very easy to work with. This solder flows very quickly and has saved me many times from damaging components. The Cardas solder is a tin/lead/silver/copper mix and it is what I use for all of my cable and electronics projects.

Adding the resistors to the 6V6 tube socket is easy, but you will want to ensure that you have a pair of needle nose pliers. It can be tricky to navigate inside the chassis when you have the main board inside, and youíll want to be extra careful that the iron tip doesnít hit anything important! You might also notice that when the directions call for you to widen some of the holes on the PCB that the drill bit they call for may not widen out the hole enough. We found that some of the wires were a little too thick for some of the holes, so Phil ended up stepping up to the next bit for some extra wiggle room.

The center tap lead of the power transformer ends up being soldered to the underside of the main PCB board. The directions are not 100% clear on how to go about this, but with a little reading we found that you would need to scrape off some of the coating on the board till you get to the trace below it. For this part, youíll need to go slowly and may not want to use the Dremel, as you will not want to cut or damage the trace below.

Once you have completed all of the steps on the board, it is helpful to double-check your work to make sure there are no cold solder joints or messy wires. This is the time to do any clean up on the board and neaten the wires. The directions include tips on making the interior nice and neat. Again, stray wires can cause you an unbelievable amount of trouble. You may also want to verify continuity on the trace cuts and the new parts that you soldered.

The other piece of equipment youíre going to need for this modification is a Variac and if you donít own one, youíll need to borrow it. So why exactly do you need one? The Variac will allow you to slowly bring the amplifier up to its operating voltage so you can monitor the amp using a voltmeter to ensure that everything is working correctly. In this case, we pulled the fuse and metered across the terminals to ensure the amplifier was maintaining its correct working voltage. Had the voltage gone past the correct level we could quickly and safely cut the power and not damage the amplifier. If there is an issue you will see the voltage spike well above the recommended level as you are turning the variac up. Also, if you happen to start smelling smoke as you turn the Variac up then youíll want to immediately kill the power and double check everything.

After we verified that the amplifier was working at the correct voltage it was time to plug in and turn it up! Right from the get go, you could tell that the Mercury Magnetics kit had brought new life into this little amp. The tone was immediately complex and rich, not loud or brutish, but smooth and inviting. There was also the immediate feeling of success; there is just an all around good feeling when you complete a project and hear it working for the first time.

The Upgrade in pictures -- click on each of the following to see a full-sized version.

November 02, 2009 | Paul Zoskey of

Mercury Magnetics Upgrade Amplifier Shootout: Part 1 -- Valve Jr.

Mercury Magnetics Modifed Amplifier Shoototut: Epiphone Valve JR
from GitFix on Vimeo.

With the Upgrade to the Epiphone Valve Jr. completed, it was time to see if we could hear some differences. We decided to take the amps up to Phil's home studio and set up a proper shootout. To switch between the heads we selected the Radial Tonebone valve tube head switcher, as it would allow us to use only one cab. All of the cables were matched in length and brand type to make sure that the comparison would be as color free as possible. We used a Shure SM57 microphone into an API 512 microphone preamp into Phil's analog mixer, and out of the mixer into the cameraís XLR input. For the guitar we used a Colling 360 with Lollar mini humbuckers. This setup allowed Phil to switch between the heads quickly and without any tone loss.

With the amps set at roughly 10 o'clock you can already hear a real difference between the heads. The stock amps sounds all right when you first plug into it, especially when you look at its price point. But as soon as you switch to the Mercury Upgraded head you hear just how much of a difference the modification makes. It is not just the over all volume that has changed, it is the fullness of the tone. The signal sounds full and rich, and the string-to-string definition leaps out at you. If you simply focus your attention to the bridge pickup, you can hear how much more pleasing the Mercury head is to the ear. The stock Jr. feels choked and thin and to my ears, the break up is harsh. Like the microphone that is recording the guitar distorting, as opposed to the distortion coming from the amp.

There is nothing like a little Led Zeppelin to help you illustrate a point, in this case "Custard Pie" was just right. With the amps set half way, or 12 o'clock, the high frequency clarity of the Mercury really stands out. This is most apparent when you are in the bridge pickup; the stock amp sound very mid-rangy and almost muffled, like there is something covering the speaker cab. When you switch to the Mercury the sound is immediately more open and clear. The additional high frequency that you can hear is really amazing. The bridge pickup shows you how tight the sound can be, and the overdrive sounds just right to me.

It is interesting when you consider how good the stock Valve Jr. sounds on its own. The amp is not too bad at all, you can get some good tones out of it and it is loud enough for recording or maybe a small club. But as soon as you put it head to head with the modified version, you hear just what it is missing -- harmonics and dynamic range. The ZZ Top lick really helps to illustrate my point, you can hear just how rich the harmonics are when Phil switches over to the modifier head. The same riff played on the stock head just doesnít seem to produce the same amount of harmonics, and generally sounds dull and flat to me. I think this volume on the amp, between 2 and 3 o'clock, produces the best tone for the amp. It is the perfect tone for blues and rock. You could always throw in a boost pedal if you wanted to push the amp a little harder for increased sustain.

The last setting we compare on the amp is the obligator "maxed out." At the max setting both amps are easily distorting and have a good amount of gain. I find that this setting is a little overboard in that the tone looses some of the detail and richness. You can still hear the added complexity that the Mercury Upgrade adds along with the top end richness, but the gain seems to overwhelm the tone. I think that the optimal setting for the amp is at 2-3 o'clock, that is where the amps sounds the most full and detailed. A boost pedal would be perfect if you were looking to pull some more gain out of the amplifier.

In the end I think that the difference between the stock amp and the modified amp is very easy to hear. And it is based on that fact that I think this is such a great product, you hear the benefits without the need to really concentrate on what you are hearing -- it jumps right out at you. The modification takes an amplifier that sounds good when you look at its price and transforms it into something that is unbelievable for the price. The Upgraded Valve Jr. is an amplifier that you will play for hours and hours without any listening fatigue and I highly recommend that you check it out.

Be sure to check out our second shootout of the stock vs. the Mercury Upgraded Valve Jr. with Mike Sopko playing a LSL Telecaster to coax some sweet vintage tones out of the amp.

November 03, 2009 | Paul Zoskey of

Mercury Magnetics Upgraded Amplifier Shootout: Part 2 -- Valve Jr. Shootout

Mercury Magnetics Modified Amplifier Shootout: Valve JR Shootout Two
from GitFix on Vimeo.

Most of the demonstrations that I have seen for the Epiphone Valve Jr. are done with a guitar that has humbuckers installed. I though that it would be interesting to show the differences between the stock Valve Jr. and the modified Valve Jr. using a guitar with vintage voiced pickups (read: lower output). It also seemed appropriate to include a good amount of lead work in the review so all of the lead players out there could get a better sense of what this amp could do. So I called on Mr. Mike Sopko to run us through the Epiphone Valve Jr. shootout, this time using an LSL T-bone 52.5 as the main guitar to hear what lower output single coils sound like. We also threw in a Les Paul at the end with a lot of lead playing too for good measure!

Starting with both amps set to roughly 10 o'clock and using the LSL's neck pickup you can hear that the lower output single coil pickups are not over-driving the amp as much as when we were testing the amps with the Collings 360. But you can hear how there is certainly more breakup when Mike switches to the Mercury Upgraded amp. The overdrive has a very round and open character to it and again, the top end comes through right away.

We then set the amps to 1 o'clock to get some more distorted tones out of the amplifier with the LSL. Starting with the stock amp you can hear the tone is muted or dull sounding. To my ears the tone is dark, not warm and I find the overdriven sound to be a little weak and thin. The Mercury Upgraded amp adds detail and presence to the tone. I find the attack to be more pleasant to my ears; when Mike digs into a note, the growl from the amp is more open and rich. The sustain of the individual notes sound bigger with the modification, while the stock amp sounds like it is letting go of the note almost immediately. The Upgraded amp lets each note ring on longer without such a quick decay.

One of the more interesting aspects of this shootout for me is to see how Mikeís playing and expression changes when he switches between the amps. With both amps set to full you can see Mike start with the stock amp and work his way through some lead work and chords. But when he switches to the Mercury Upgraded amp you can see that he is almost immediately more involved in what he is playing. He actually starts grinning around the 4:53 mark in the video. You can see that the response, attack, and tone of the amp make it more exciting to play. In the previous Epiphone shootout there seemed to be less difference between the two amps when they were set to the maximum volume using humbuckers. But with the LSL you could really hear the difference that the modification makes to the dynamic range of the amp. With the modified amp you can hear all of the notes ringing out, and chords sound full and detailed.

I thought it was important for people to hear some more lead work through the amplifiers, as it would be a good illustration of what the Upgrade adds to the tone. When you hear Mike run up and down the neck through the stock amp the notes sound downright fuzzy, there is not much clarity. This would be fine if you were using a fuzz pedal, but I doubt you would want that fuzzy sound on everything you were playing. Itís always better to start with something that is clear and detailed thus allowing you to dirty up or fuzz up the signal as you see fit. When Mike switches to the Mercury the notes clean right up and there is a new level of detail to them.

So once again we see that the Mercury Upgrade takes this budget amplifier and transforms it from something that was once a disposable import into something that you will keep and play for a lifetime. Mercury Magnetics has really done something special with this upgrade kit and I think it is something that you should check out.

Mercury Magnetics Amp Shootout: Champ "600" vs. Valve Jr.
from GitFix on Vimeo.

November 6, 2009 | Paul Zoskey of
The final shootout! Mercury Upgraded Champ "600" vs. Valve Jr.!

For our final Mercury shootout it seemed fitting to pit the Champ "600" square off against the Valve Jr. Both amps clearly benefited from the Mercury Upgrade, but does one stand above the other?

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