I'd like to help, but these amps have not been out long enough for mods to catch up. I'm sure you could take it to someone like Dave Freidman or the like that could do it. Or a good amp tech would probably know. I would check with local amp techs in your area.
About tubes: I have the stock tubes and thought about buying new ones so I had if the current ones go bad. I play mostly clean, lo-gain and med-gain, blues and classic rock - Should I just buy 3x JJ 12ax7 and a matched pair of EL84, or is it worth trying out 2x 12ax7 and 1x 12at7 for an example? I have never thought much about tubes before...
I have a JCA20H and matching cab that will be here on Tuesday or Wednesday of next week. I installed a Zero Loss effects loop in my Metro JMP50 and plan on doing the same with the JCA. It will probably be a few a few weeks before I get to it and will report back when it's done. You can get the loop at Metro Amps for about 90 bucks and it works great.
Bumping this old thread, I know. I'm getting the combo later this afternoon, and I'm very interested in hearing about the mods. Specifically, the effects loop, depth, choke, and bitmo mods. If anyone has some info or reviews about them, I'd love to hear them.
I've seen the schematic details on the mods, but I'm not real good at reading schematics. I'm better with pictures and instructions. Like, "replace the X value resistor at R29 with Y value resistor".
I second that! I just got my Friedman Modded JCA20H yesterday. I have not stopped playing it! I got the one without the loop plus the saturation switch. It sounds mean without the saturation switch on. But when you turn it on Holy ****!!!! Mine has a bit of tube rattle. You really can't notice it, but I can. Still has the stock tubes in it. Plan on swapping them out with JJ's. That little thing really growls! I have Rio Grande Humbuckers and it sounds fantastic! Really nice string to string clarity thru chords at high gain. Also, roll your volume knob off and it really cleans up pretty well. Still has a bit of grit though. Want to try some ceramic humbuckers to see if I can get a tighter bottom end. Sounds great with anything you plug into it. Considering getting another. Way loud enough to gig with. Especially, if you run 2 in stereo. Maybe get the other one with a loop. I have the Egnater Tweaker and it has some great sounds for sure, but the Friedman sounds better to me!