John, my dad did have a cheater plug, and the hum remains when I use it.
Bummer. Your amp is bad. Could be something real simple, like a loose connector. Might be worth a few minutes of your time to pull the lid and look around a bit. But I suspect there's something more going on.
John - the hum can come from noise on the neutral, not just your typical ground loop. 110v > 24v transformers being powered from the same power source can cause this hum too. I don't fully understand why or how this chatter / hum is picked up with an amp. I can demonstrate this to you on two of my systems that use an outboard amp though. No hum with the AVR powering the speakers, hum when adding the amp(s).
