I put together a 7.1 surround set-up a ffew months ago and have had 1 nagging problem. Whenever the Co-ax from TImewarner is connected, if my sub is on it gives off a low hum (sounds like a ground loop). I have tried grounding the receiver with the coax thinking that would work. I have tried numorous power conditioners (including some with coax in & out), still not fixing it. Any thoughts on what is going on and how to fix it? Time Warner says "if your set is not humming we will not fix HiFi issues."