Originally Posted by Dan in St. Louis
First find out what devices are separately "grounded" so you know where you can break the loop.
You have identified one as an amplifier with a 3-pronged plug, so one way to break the loop is to put an adapter on that plug so only the 2 power prongs are used.
Another possible ground is incoming TV cable. That puts the STB at a different "ground" potential than your house wiring, and via the HDMI or audio cables the receiver will be at that second "ground." You can verify that by disconnecting the STB coaxial feed. If that helps you could look for an isolation RF transformer for that cable, or make sure that it is solidly grounded to the same ground as your house wiring.
A third possibility is the TV. If you have an outside antenna the installer may have grounded its coax also, so there could be 3 different "ground" potentials in your system.
The most solid ground is probably at your electrical service entrance and you may spot a heavy gauge wire attached firmly to a cold water pipe (or a rod driven into the soil if you have plastic pipes). Everything else that needs a ground should use that one. You don't want to go into the breaker box -- just clamp to the same pipe or rod.
I don't have any TV or coaxial cable. Just a projector and blu ray player connected. Everything is plugged into the same panamax, so same circuit.
I gave up on the trigger issue but now still have a problem with a low buzz from the speaker tweeter.
My Denon preouts will be silent but as soon as I plug in any device that :
1) a ground prong AND 2) an interconnect that goes to the AVR (RCA/HDMI).
as soon as I plug any of these in I hear a buzz in the speakers. To make the buzz goes away I need to unplug them.
One of the buzz causer is the projector and the other is an 3 prong external amp (they doesn't need to be on and it buzz). No problem with anything that has a 2 prong plug (2 prong amp or 2 prong DVD player)
Strangely enough the buzz is only in the center and surround speakers, the LR are not affected.
I tried to add a chassis ground from the denon to the ground on the panamax (measuring a few ohms jumping on and off), that does not help, actually makes it slightly louder and make the LR also buzz! The denon is saying : I don't like anything that have a 3rd prong ground, whether ground the interconnects or a direct wire to the chassis, makes it buzz more.
I tried a humX on the projector but it does not change the situation. Seems like the buzz is low enough (not a hum) the humX let it through, seems like humX put a little resistance in the ground pin but still let fault current through.
Next thing is trying a ground lift plug. But if used permanently and there is a fault the current will go to all the interconnects and fry everything.
But if you have any ideas I will appreciate it. It is bearable because it had been a while now I just thought it was coming from the transformer of the external amp, but after hearing it without the 3 prong electronics plugged in I want to try to fix this.