I will check the work outside tomorrow..All my audio equipment is plugged into a decent Tripplite Surge unit on the same circuit that feeds the theater room as the subs are plugged into, not the same exact outlet. From what I've read you can have two pieces of equipment with 3 prong (grounded) outlets on the same circuit, but the loop forms when you connect those two with another cable, which is also acting as a ground.
The HD receiver only has a two prong plug, so not sure if that is part of the problem. I need to play with some things but as soon as I unplug the HDMI cable to my receiver, the noise goes away, or if I unplug my front subs from the receiver.
M80s-VP180-QS8s-EP600-2xEP350 Denon3808 Outlaw7700