Hi JohnK, yeah Brent from Axiom thought along the same line as you as well. He send a replacement AMP that was modified to accept 50 and 60Hz. I'm guessing it's what you send about power supply being polluted. Tonight I actually was able to bring home an UPS that has a warning light on the back which comes on if the AC power supply is bad or not ground correctly. I plugged it in to all the AC outlets and the light came on every time. I tried the sub plugged into the UPS too and got the same hum. So I could been stuck with this problem maybe.
