So if I plug my ARC Classic 60 into the wall with the speakers hooked up and turn it on I get no buzz. Please note that no other equipment is plugged in NOR are and interconnects attaches to the amp or any other piece of equipment.Your getting an "open circuit input buzz", if you put shorting plugs into the input, the buzz should go away, same if you have preamps cd players or dacs connected. (The input needs to see a load)
Cheers George