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Epiphone Valve Junior (combo)
MUFF WIGGLER Forum Index -> Guitars, Basses, Amps & FX  
Author Epiphone Valve Junior (combo)
I just picked up one of these bad boys on a special $100 deal (normally they're ~$150), and wow!

It's a single ended, 5 Watt, Class A tube amp based on a 12AX7 and single EL84, with an 8" speaker. There's a head version too, but I opted for the combo.

Now, I haven't played every amp in the world, but I'd put money down that this is the best sounding amp for the money, bar none! It certainly has some room for improvement, but it's no frills simple design leads to a great responsive tone.

Initially, the only downside I see (or, uh, hear) is that the speaker is a little weak...or maybe it's some of the gain staging...but it's a tad on the boxier side.

Either way, there are dozens of possible "mods" published on the web for it. After reading a bunch of them and looking at the schematics, I think I'll just be changing a few component values and maybe adding a switch here and there. People are saying the output transformer is too small for this amp, but it's bigger than I I don't know what that is about.

Either way, bone stock, this thing is an amazing deal and really fun to play. Highly recommended!
Chuck E. Jesus
how loud is that thing? i only tried the head out once thru a 4X12 cab, and it was very loud (i hit one cord at Guitar Center and everyone looked up...this was Guitar Center!)...from what i understand the head has some improvements on the combo, but i probably couldn't tell the difference either way...but yeah, the mods are said to bring it to boutique amp tone quality...
It's quite loud for its size...turned all the way up I'll approximate that it's at least 100dB. I bet it would easily keep up with a full band if plugged into a larger set of speakers (the internal speaker is actually hooked up via jack, so you can unplug that and hook up a different cabinet.

The first version of the combo had some buzzing and hum problems which were fixed in the head when it was released as well as the next version of the combos. I have one of the latter versions of the combo and it has no noise problems whatsoever...only the standard hiss you get from tube amps when it's turned up loud (easily on par, if not quieter than my tripple rectifier). The easiest way to tell the newer combos from the old is they have a nylon shaft input jack...the older ones were all metal, part of the reason for the hum.

Even without being a electrical engineer I can see some shortcomings of what they did. First off, there is a pull down resistor after the input, but it is only 68k, so a signifant amount of the signal is getting bled to ground before being aplified by the first stage of the 12ax7. A similar thing happens before the next stage and finally again before the EL84. Again, I'm no EE, but doing that same kind of gain staging on a mixer for example make the sound much thinner and less punchy. Now the valve junior doesn't sound bad at all, but thickness and punch are its weaker qualities.

I'm going to try and start working it later today...its hard though because it's so fun to play right now haha!
Muff Wiggler
that's freakin' awesome. For $100? shit dude. well done
I completed several of the mods I sketched out today and, wow, what a difference!

The first thing I did was replace the stock no-name speaker with a Jensen C8R. This made a drastic difference! The top end sparkles a lot more, the midrange is much more clear and defined, and the low end is much tighter and less "farty" on the low E and A strings. The only downside is there is a little less bass compared to the stock speaker, however, this is an acceptable sacrifice for the drastically better tone.

Next I switched out the tubes with some JJ/Tesla replacements. Unfortunately, because I'm and idiot and accidentally ordered EL-34s instead of 84s, I only was able to replace the 12AX7. This made a pretty marginal difference, barely audible really.

Next, I cracked open the amp and started work on the heavier mods. First up was to replace the 68k R2 pull-down resistor with a 1M ohm resistor. I also removed the 68k resistor input resistor altogether. This made another huge difference in the tone. The amp became a lot more responsive and punchy. The sound really "tightened up" overall. The upper mids also cut a bit more than before. The only downside here was that the slight hiss that the amp had always exhibited got louder. Again, this is an acceptable sacrifice for the difference in tone.

The final mods were to replace the 1M ohm R6 resistor with a 1M potentiometer as well as put a switch after R7 to break the path to ground. Both of these changes together allowed for a serious boost in gain. Not enough to actually cause distortion like I thought, but enough to really increase the punchiness and bite of the sound. Using the switch to break off R7 and it's connection to ground adds a nice subtle boost, but a noticeable addition of punch. As you roll down the resistance of the 1M pot, it gets louder and a little punchier. The only downside here, is the noise floor obviously gets louder as the gain goes up. The switch doesn't make as big a difference as the 1M pot does you can still switch in that additional punchiness without a perceived increase in hiss.

After those mods, I stopped. It sounded so much better than before I was satisfied with that. Also, I wasn't as sure what the tonal impact would be of the other mods so I took a "if it ain't broke, don't fix it" approach and left those on the drawing board.

All in all, I only spent about another $60 (and would have been less if I hadn't ordered the wrong tubes) on this $100 amp and it literally sounds like a $400 amp now. I'm extremely impressed with this little guy, and I can't stop playing it!
Wow :shock:
Really looking forward to hearing it!
Cool documentation notes 8)
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