I finally opened up my Concert II and took out several of the caps bridging the preamp tubes, rearranged a few of the leads, and changed out a couple of tubes, and am very pleased with the results. I now actually like the overdrive (sounds like a Boogie), but the clean channel is not quite to my taste yet. If I can get the clean to sound like a blackface or tweed Fender and the overdrive into Dumble territory I'll quit. I know Dan Torres has a "mod kit" out for this, but I'd rather not blow the $50, and it sounds like his mod is more drastic than I'd like anyway. I really don't like the idea of one master volume for both channels. I also don't think the Jackson mod really does what I want either. I have the schematic but with the switching being somewhat complex I have a hard time following the signal through it in different modes, otherwise I'd make a stab at tweaking the preamp a bit more myself. Any suggestions? If anybody has a copy of either of the above mods they'd like to give some details on I'd be interested - maybe I can incorporate some of what they did. I also don't understand in this amp why Rivera in 2 places ties both sides of a 12AX7 together and runs signal through both as if its one gain stage - it seems he wastes a whole tube that way. (and he DOES waste half a preamp tube later) I know I was advised to leave the amp alone, but I'm an inverterate tinkerer and couldn't help myself. I now plan to try rearranging the overdrive preamp tube component values to more "Dumblelike" specs and am considering using the unused half of tube to give one more gain stage in the overdrive mode. I'm also thinking I'll change most of the preamp to metal film resistors and solid core wire. The problem I think I'll run into is that the amp is fairly complicated, and I'll probably run into noise and oscillation problems as I proceed. I might be better off to simply put the caps back in, sell it and buy a Two Rock or Fuchs later (but I'm also a cheapskate). Any thoughts?