ok so far I haven't really recived much help. I have a JCM 800 4210 that sounds like crap. the distortion sounds very muddy and it hums like crazy! the clean channel isn't terrible but it could definitly use some help. I have replaced all of the tubes and properly rebiased the power tubes. I know the dangers of working on tube amps and I know how to aviod getting shocked by discharging the amp. I would love to just take it to an amp tech but there isn't one with in 1oo miles of me. I have looked at some schematics but I am just not very good at reading and following schematics. I have done effects mods using a book from indyguitarist.com and I found those instructions to be very easy to follow and made the process fun.