Blown fuse, cap, resistor?

after months without music, sending all my equipment to get upgraded, repaired, i finally got everything back, hooked it all up, and everything is sounding ok. after some moderate listening, i turn it up to see how far i can push it, and one channel suddenly drops in sound level. it still plays, but much more quietly than the other channel. this also is the channel where the amp is plugged into the same outlet as my BPT 2, which powers my digital/preamp. i still need to get dedicated circuits, i'm guessing there was a power dip? anyway, i'm trying to figure out what went wrong. i'm pretty sure it's that channel's amp, as the other channel sounds fine. could it be a blown cap, resistor? god i'm so friggin bummed, after all time waiting...