Over the last few months, I have noticed a buzzing sound coming from my Carver C1000A. The sounds starts out very low and then gets progressively louder. It goes away if I power cycle the amp a few minutes but usually returns.
I have a Monster power conditioner powering all the components-it also reports everything as grounded properly!
Can't tell you for sure, but my best guess is that the power supply capacitors are in need of replacement. When mine died, the first things I noticed were unexplained hum problems (that actually got worse when the amp was plugged into a grounded outlet) and thin sounding bass.