Hey guys. I just finished a nice theater with an APC S10 balanced battery backup solution--> Marantz AV7701-->balanced outs to Outlaw 7700.

There is a 60 Hz hum in the background (does not vary with volume) but can be heard faintly, really only when paused or volume is all the way down. You can hear it in the subs and high overtones in the tweeter.

Problem goes away completely when I power my rack straight from the electrical outlet and not by the APC.

Bad APC? I have tried all the different kinds of outlets on it and connected the ground stud to the rack chassis. Don't know what else to do besides try a different one and those things are a back breaker when you fly solo!