"Update on my Valve Jr. upgrade! Wow, nothing but kick ass, balls-to-the-wall tone!" -- Gilbert Cruz
That set us to thinking about conducting an A-B test on a fundamental guitar amp. One with only the minimum components to do the job. Hummm....
 After a little digging around we found our guinea pig -- the Epiphone Valve Junior Combo. Talk about your fundamental (and remarkably inexpensive!) tube amp. Check this out:
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5 watts
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Single-ended, Class A
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One generic 12AX7 preamp tube
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One generic EL84 power tube
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Generic power & output transformers
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Generic 8" speaker
Epiphone's Valve Junior Combo proved to be an almost ideal demonstration platform because it is such a basic, stripped-down tube amp. Just 2 tubes, 2 transformers, 1 speaker, a simple circuit board and just a handful of other parts -- along with 1 input jack, 1 volume knob and an on/off switch. That's it, no computerized components, no tone knobs, no added f/x circuits, nothin'... you just can't get any more elementary and still have a playable tube amp!
All this for about $139.00 for about? Yes, but as you might expect, the stock amp is anemic and thin sounding -- not exactly an inspirational amp. Let's see, what can we do about that....
Side note: It should be mentioned that our goal wasn't to build the perfect amp, only to demonstrate the effect of quality magnetics. But it quickly became apparent that we'd transformed the little Valve Jr. amp into an extraordinary "I've gotta record with this!" keeper. As the demands poured in we decided to develop the Mercury Mod into a kit and make it available to the general public.
The Mercury Mods....
The project was headed by Mercury's Sergio Hamernik, and Los Angeles-based amp tech wizard, Alan Cyr (www.Amp-Exchange.com). After examining the original circuitry several custom
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