Champ 12 Upgrades

I have my Champ 12 opened up to do the Torres input jack upgrade. "While I'm in there..." there are a few other things I'm going to do, looking for other suggestions. I really only need the normal channel (plenty of pedals get anything else I want), but I wouldn't mind trying to tame the distortion channel a bit. Years ago I did put in the Torres mod that links up the two preamp tubes with a few resistors and caps. I think its purpose mainly was to try to balance the two channels (a little more normal, a little less drive)?

I want to recap while it's open, at least the four big 47s- most likely go up to 220? Any need to do the other four smaller electrolytics?

I can't find any smaller value pots that will fit in for the two 1M drive channel pots, but I do have some 330k resistors that I can put in across the outer lugs- I think that's a known mod to give those pots a more usable range?

I'll try playing with the reverb trim pot, but again I have a decent reverb pedal so no biggie.

I wanted to replace the power switch with a typical Fender toggle, but after looking it over it's a bit tougher than I thought- faceplate-wise. Like fitting a round peg in a square hole...

I've printed out two or three marked up schematics of other guys mods, but I don't want to just start changing things "willy nilly".

Suggestions?

This link was very helpful, particularly for tracing out the signal path (good ol' robrob again):

https://www.tdpri.com/threads/explain-the-champ-12.691445/



(ignore the stuff to the left, also building the Smallbear Maestro FZ-1 clone).

 

No, I got it 6 or 7 years ago (while he was still selling kits). "Just getting around to it..."

 

I was thinking about that cap swap.

And I've read how the amp is very responsive to tube changes.

 

OK, I replaced all the electrolytics. Upped the filter caps from 47 to 100uf. The MOD caps were the only ones I could find with the same dimensions for the tight real estate of the boards- any experience with them?

I changed the tone stack caps to 150 pf mica, .047uf, and .022uf as per the Premier Guitar article.

I replaced the plastic jacks with switchcrafts, and I put 330k resistors across the two drive pots give them a little more operating room.

I was toying with the idea of making the Torres mod that I had put in years ago switchable by adding a mini-toggle on the back panel, but now I'm not so sure. Looking at it a little closer (and with my newfound amp understanding- danger danger....), I think all it is is an additional cathode resistor and cap for both V1B and V2A? I don't know if they're working together, or both can be independent of each other? You really would need two switches one for each resistor/cap right? And it might just be snake oil anyways?





Torres mod:

https://torresengineering.stores.yahoo.net/redcham12kit.html

 

Done. Sounds really nice! Quiet as a church mouse. Distortion channel is much more usable, pots have enough range now that you can start off with just a hint of "edge", and balance it with the normal channel. I'm liking the normal channel mid boost setting.

The other improvement I added was the Torres tube set that I had ordered years ago but never put in. I don't know what the 6L6 is, the preamp tubes are a Mullard and a Sovtek.

At some point I might try removing the "Torres mod" from the preamp tubes to go back and hear it now without it. Many say it helps the distortion channel at the expense of the normal channel.

 

Yeah, very quiet. With my 70-year-old ears I have to get down on the floor with my ear near the speaker to hear any hum.