I'm having a little bit of a problem with my 5.1 channel system (pre/pro plus 7 channel power + 3 channel power, using all channels of the latter power amp and two of the former). Every now and again I hear a little bit of distortion from one of the speakers. Not often, maybe once a day or once a week, and only for a few seconds, so it is hard to troubleshoot. It doesn't sound like a failing electrolytic cap, it can happen when there is no signal, the volume of the distortion is the same regardless of how much loud the system is playing, and can maybe be best described as somebody filing their nails for a second or two. Or getting their teeth drilled in slow motion. I ruled out the speakers and any source so blamed the power amp, so chose a different two channels to do the work of driving the rears, thinking I had one faulty channel on the 7 channel power amp. Tonight the distortion came back, only for a second, to the same speaker I had connected to one of the channels I believed to be good. At no point did I think the pre/pro was the culprit (Arcam AV8, about 10 years old) but am now starting to wonder. I can take one failed channel in a power amp, but a second one in the space of a couple of months? How likely is it that the AV8 is causing the problems? Is using only two channels of a 7 channel amp going to upset it? I wish something would just break so I would know what to replace.