Amp Started Crackling - What to Check For?

[Josh]

Just noticed that one of the channels on my two-channel amp (which drives my surround channels) is crackling, even when no sound is being fed to it by my receiver. Just the fact that its on makes it crackle. The sound from the TV and Blu-ray player still comes through, but the crackling is very audible.

I've already tried swapping cables and wires and even trying another channel from the amp with no solution. I definitely narrowed it down to the amp.

I openned it up this weekend, and nothing is looks amiss on the circuit board. The transformer looks fine, the capacitors are dry, and none of the resisters appear to be burnt out. What else should I look for as a possible cause?

Its an Acurus A80.