Bugera V22 Mods

I got a Bugera V22 early last year, for around $350 Canadian. I had to wait a few month for Bugera to ship it, but for the price I could wait. It's basically a Peavey Classic 30 with less power; it has 3 12AX7s and 2 EL84s for (allegedly) 22W. It's basically the cheapest non-practice tube amp out there. Which of course makes it a perfect modding platform.

The amp sounds pretty good to begin with. It can be a bit ice-picky, but that seems to go away as the speaker breaks in. The clean channel is great, with a wide, open sound, although it has a bit of a upper-mid boost that isn't always desirable. The overdrive channel is less impressive. It's chunky (in a bad way) and it has a big mid hump (lacking bass and treble). Some people like it, but I don't. So my mods tried to fix all of these issues, along with a couple others.

First, here are simplified schematics for the amp. They don't include switching, reverb, the bias supply, etc.
Preamp
Power Amp

And here are the mods I did.
Modded Preamp
Modded Power Amp

And here is a sound clip, mainly for the OD channel:
Sound Clip

New: A forumite on tube-town.de called netbear has done a nearly full trace. His schematic includes the bias supply, switching, and heater wiring. I admire his patience.
Eagle file
Image

Note: Do not work on amps unless you know how to handle the high voltages present safely.

OK, going from input to speaker, here are the mods.

Clean channel

I reduced the cap on the Bright input to 3.3n. This makes the input sound like less of a bass cut, and more of a treble boost. Note that this reduces the signal level.
I removed the 1n cap before the Clean Volume pot. This gets rid of the upper mid/treble boost that the clean channel has. This also makes the bright input more usable. The channel is still pretty sparkly, but the treble isn't as overpowering.

OD channel

I increased the OD input capacitor to 2.2n to increase the bass in that channel.
I removed the 470p capacitor to ground at V1b to increase treble.
After the other mods, there was some blocking (farty) distortion at V1b, so I put in a 100k grid stopper.
I increased V1b's cathode bypass capacitor to 22u, again for more bass.
I put a 1n cap to ground at V1b's plate to soften out its distortion.
I increased the next coupling cap to 10n for even moar bass.
I removed V2a's cathode bypass capacitorto lessen its gain.

These mods make the OD channel more useful IMO. The high gain tones are pretty messy (not necessarily in a bad way), but the crunch tones in the first half of the Gain knob are much sweeter and without the big bass and treble cuts. YMMV.

Power Amp

I threw in a 470k grid stopper on the advice of The Valve Wizard.
I cut the ground trace on one of the EL84s, and put in a 1 ohm resistor. I rewired the bias test output to connect to either side of the resistor, so I can now bias one of the tube to 22mA idle, then swap the power tubes and check the other one. This lets me bias accurately instead of using Bugera's method.

There you go. The OD channel is the trickiest one to get right, but I'm happy with what I've come up with. Mod away!