Boutique-quality TONE for less than $400?(!)

Inside of all the greatest-sounding amps ever built lies buried treasure. The source of this profound and amazing amp tone is the transformers. Pro-quality transformers are not easy to build and they are also comparatively expensive. When an amp builder is unaware of, or chooses to ignore this fact by installing cheapo transformers, the tone of the amp tells the tale.

If you find playing your amp fatiguing or just plain boring, if your childhood memories of Uncle Bob's "armpit fart concerts" sound better than the amp you're stuck with, then you are probably an unwitting victim of tonally anemic, low-budget transformers.

To help prove the point, Mercury designed an Upgrade Kit for the remarkably inexpensive Valve Jr. amp (combo or head). This demonstration Upgrade Kit features high-end, pro-quality performance transformers like those in great-sounding amps costing anywhere from hundreds to thousands more. Our Upgrade Kit makes the modified Valve Jr. the lowest-cost introduction ever to the wonderful world of boutique amplifier tone.

Ever wonder how much better YOUR amp could sound just by Upgrading its transformers? Here's your chance to discover the night-'n-day difference.

You can experience pro-grade tone with all of the feel and expanded range-of-control the pros enjoy -- without draining your wallet!

The Upgrade Kit that will change forever how you define guitar tone

"If my place caught fire, my Mercury Upgraded Valve Jr. would be one of the first things I'd drag out to the sidewalk... despite the low cost."

-- Bob Dragich


I finished the Valve Jr. Upgrade over the weekend. AMAZING!!!!!!!!!! I have been playing guitar for 21 years and this is, without a doubt, one of the best amps I have ever played -- and it only cost me $400 total!!!!! Unbelievable!

I have a new found respect for the iron that is used in all my amps, and more specifically for the fine people/engineers at Mercury. Way to go!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"

-- Jonathon Short

"Update on my Valve Jr. Upgrade! Wow, nothing but kick ass, balls-to-the-wall tone!"

-- Gilbert Cruz

"The amp tech was floored. He couldn't believe the tone. I highly recommend this insanity!"

-- Craig Lunsford

"Holy smoke, I thought the amp was going to get up and walk around!! Very, very impressive complete tonal spectrum sound! Nice job."

-- Marcus Earling

"I A/B'd the Mercury version of the amp against a stock Valve Jr. head, and found it hard to stay plugged in to the non-modded version amp. I must say, the Mercury Upgrade might be a bit pricey, but it is truly worth it. For the cost of around $400, I have one of the best recording amps on the planet. Believe me, I have tons of vintage amps, old Marshalls, Fenders, Ampegs just to name a few and this little baby just kills! You could use it at a gig with it miked, and you'll be the envy of all your guitar player buddies. As for me, I can't stop playing it, very cool!"

-- Phil Antonucci

What is the Mercury Upgrade?

It's the result of a guitar amp tone transformer demonstration project that was headed by Mercury's Sergio Hamernik, and Los Angeles-based amp tech wizard, Alan Cyr ( The Upgrade is simple, requiring only the replacement of the existing transformers, the addition of a Mini-Choke, and a simple rework of the circuit. And for the more daring and adventurous, an optional "6V6 tube mod" is included that will radically increase the tonal choices of the amp -- FREE!

The result is a remarkable harmonically-responsive and toneful little amp that runs quiet and sounds B-I-G.

If you are an experimenter you may want to try different speaker and/or tube configurations -- but interestingly enough, those components deliver relatively minor tonal changes compared to the absolutely H-U-G-E improvement of the Mercury transformers.

Our Upgrade Kit transforms the bland little Valve Jr. into a keeper. Here in Los Angeles, the Mercury Upgraded Valve Jr. is one of the hottest, most in-demand insider amps around. Those who've heard it immediately want it -- and at such a low cost to make the mods, who can afford NOT to! It's no wonder so many first call LA session players have grabbed them up!

How easy is the Upgrade to do?

To make the Upgrade yourself, you'll need basic electronics skills. Always keep in mind that working with electricity is dangerous and potentially life-threatening. Please do not take this warning lightly. That said, the project is very straight-forward and extremely well documented. But if you're not up to the task, give us a call and we'll put you in touch with a Mercury authorized amp tech who can help you out. There are plenty of Epiphone Valve Jr. amps around on eBay. Likewise Guitar Center and are also known to discount. Another choice is to build your own -- check out the site for a hand-wired, point-to-point kit.

Great news!.... If you can't find a Valve Jr. to upgrade OR have a damaged PCB -- then build your own PTP (point-to-point) board! CLICK HERE....

Revolver Amps

Want to swap your Valve Jr. amp's PCB for point-to-point board? Talk to Charles at Revolver Amplication. (

The Upgrade Kit process --

Legendary Tones: Check out Mike Mullen & David Szabados' ( review and YouTube videos of their Mercury Upgraded Valve Jr..... The folks at Guitar Fixation performed not only extensive sample builds (on video) but also "shoot-outs" against the stock version of the Valve Jr. Lots of great advice and tips, too. Special thanks to Duncan and Paul. Here's a really ambitious Upgrade Kit review, complete with educational How-To video instructions. A big "thank you" to Luigi for his amazing compilation!

Sound samples and related links -- Want to hear an Mercury Upgraded Valve Jr.? Sound samples are available at Alan Cyr's Alan is the Upgrade circuit designer of this project. Note that these recordings were intentionally made under primitive conditions. Special thanks to LA musician, Phil Woodward, for all of his help with this project.

Seymour Duncan User Group Forums: Check out this thread on the Epiphone Valve Jr. plus Mercury Magnetics -- detailing a fresh build.

Mike Yankie: Check out Mike Yankie's point-to-point version of the Mercury Upgrade. Lots of sound samples there, too!

Paul Anwiler: Check out Paul Anwiler's A-B comparison clinic with a stock Valve Jr. pitted against a Mercury Upgraded version....

Steve McCabe: Check out these sound samples from Steve McCabe's before & after Mercury Upgraded Valve Jr.

Complete AxiomŽ Upgrade Kit for the "Mercury Mod" Valve Jr.

PLEASE NOTE: This is a specially developed and priced Upgrade Kit. At this time we are not selling the components individually.



    Epiphone Valve Junior Upgrade Kits
  • Axiom Power Transformer

  • Axiom Output Transformer

  • Axiom Mini-Choke

  • Other parts necessary to make the mod

  • CD-ROM with schematics and photographic instructions

  • Mercury Magnetics "Equipped with" metal plate

  • Fully illustrated step-by-step color manual, with wiring schematics on CD-ROM.

  • BONUS! The "6V6 Mod." Takes your Valve Jr. to even greater heights! Retrofits a 6V6 tube into the circuit. Allows you to run the EL-84 and 6V6 separately or in tandem.

AxiomŽ EPJR-KIT1 Valve Jr. : Complete Mercury Upgrade Kit -- single 4Ω tap ONLY.
Includes the latest "6V6 Mod."
AxiomŽ EPJR-KIT2 Valve Jr. : Complete Mercury Upgrade Kit  -- 4, 8 & 16Ω taps.
Includes the latest "6V6 Mod."


(Plus Shipping & handling)

Choose your option:


(Plus Shipping & handling)

Choose your option:

For countries other than the U.S.A. or multiple cords
please email or call
Mercury Magnetics at
(818) 998-7791


  • This is a specially developed and priced kit. At this time we are not selling the components individually.

  • All kits sold in North America are available in 120V only. At this time non-North American versions are not available.

*NOTE: Mercury's Upgrade Kit does not include the amplifier -- only the components necessary for the Upgrade of an existing amp.

Also see the Mercury Upgrade Kits for the Orange "Tiny Terror", Fender Champ "600," VOX AC4tv and the Blackheart "Little Giant" series amps.

NOTE: If you'd like to purchase an already upgraded amp, contact Alan Cyr ( Or, check with Patrick Selfridge at Mercury -- they maintain lists of amp techs who are selling completed Valve Juniors with the Mercury Upgrades. Likewise, they'll also have the names of amp techs who are willing to mod your amp for you.


For more information, assistance, quotes or inquiries:

10050 Remmet Ave. • Chatsworth, CA 91311 • FAX (818) 998-7835

(818) 998-7791

Also patrick.selfridge

Mercury Mod projects and their documentation are the result of technical investigations made by the engineering staff of Mercury Magnetics. The disclosure of the information herein may pertain to proprietary rights, and the furnishing of these documents does not constitute an expressed or implied license to use such materials.