I recently moved into an apt. and noticed that everytime I turn on my amp it send a buzz through the speakers. Currently, I am not using rear speakers and the 7500 is bi-amping the center and powering my LSi9's. I should have more than enough power. I unplugged the amp and tried running it on a circuit seperate from the one shared by my other components. It still did it. I know the standard pocedure is switching out cables and amps (I have two unsused 2200's) to find the culprate, but I am a very lazy man.