Been reading Alans's article on isolating ground loop hum/buzz in speakers, as well as reading tons of info on other forums on this subject....
My system has been dead quiet until recently. I had Direct TV installed in the house using their new Whole Home DVR setup. The Axiom Home Theater room has an HD receiver and as soon as we turned on everything, the dreaded buzz/hum from all speakers.
Here is how I can create the sound and stop it during my testing.
First of all, everything is plugged into a decent Triplite Surge protection bar, except my Outlaw amps, they are plugged right into the wall outlet. I have a 20amp dedicated circuit that feeds my HT room. My subs are the only thing that are not plugged into that, as they are in the actual room, but on the same circuit, so should be grounded the same, to the ground rod at my service entrance.
As soon as I plug the incomming coax into my HD receiver, buzzzzzz. The receiver is hooked to my Denon using HDMI in jacks.
Here are the different ways I can get the buzzing to stop.
1) Unplug the coax from the HD box.
2) Leave the coax plugged in and unplug the HDMI cable to the receiver.
3) Or, unplug my front EP350 subs from the RCA Pre Out splitter, the EP600 doesn't seem to matter.
4) Unplug my EP350's AC plug from the room outlet.
5) Also, it doesn't seem to matter if the Direct TV HD box is plugged in with AC power cord or not.
6) I also temporarily tried a cheater plug on my 350 sub's AC plug and that seems to also eliminate the noise.
So, with that being said, my research shows you can't use a Coax Ground Loop Isolater, like for Cable TV, as it does not have the bandwidth range covered for HDTV. I've also read that many people who have tried products like the Radio Shack RCA item, say it works, but attentuates and sacrifices bass frequency response for you the subs. I see other products like Hum X, but not sure they work, and cost more.
Any thoughts? It appears the Satelitte Dish is correctly grounded to the block on the outside of the house, and the ground wire is attached to the same ground rod in the yard as the main service. I've heard some people "lift the ground" on the coax, entering the receiver, but removing the ground foil on the coax connector...I hate when this stuff happens...Randy