Thanks, BP... Those adapters are an interesting choice but at $160 that's a nice camera outside that money can be used for. 
As for the update on testing... The grounds at the outlets are good to their respective boxes. Under an ohm for both. However between outlets thru out the house, there's 30 ohms so obviously the older EMT and it's many couplings thru out will have an effect.
Grounding the A/V outlet AT THE PANEL fixes the problem about 80%. The rest of the ground potential difference would be from the panel to the BI PC.
Grounding the A/V outlet at the BI PC solves the issue as well, as expected. Running the BI PC on the UPS alone also solves it.
So as mentioned earlier in the thread, the receiver has an HDMI out for on screen display of the receiver parameters to be displayed on the tv. This was suspected as the source into the receiver causing the hum. And sure enough, disconnecting this cable solves the problem. I never use the OSD of the receiver except to change some settings which is rare once set up. So I'm using that as my solution. No more HDMI to the tv which isolates the two. If I need the OSD, I'll reach back and plug it in temporarily.
As a final thought, I observed the tv has a 2-prong plug (non-grounded) and the receiver has 3 (grounded). In my research, floating vs grounded equipment can do these things. Hope that helps someone in the future.
I'll still keep my eyes open for other solutions going forward. I prefer to minimize adding power cables unless absolutely necessary.
Thanks, all!
As for the update on testing... The grounds at the outlets are good to their respective boxes. Under an ohm for both. However between outlets thru out the house, there's 30 ohms so obviously the older EMT and it's many couplings thru out will have an effect.
Grounding the A/V outlet AT THE PANEL fixes the problem about 80%. The rest of the ground potential difference would be from the panel to the BI PC.
Grounding the A/V outlet at the BI PC solves the issue as well, as expected. Running the BI PC on the UPS alone also solves it.
So as mentioned earlier in the thread, the receiver has an HDMI out for on screen display of the receiver parameters to be displayed on the tv. This was suspected as the source into the receiver causing the hum. And sure enough, disconnecting this cable solves the problem. I never use the OSD of the receiver except to change some settings which is rare once set up. So I'm using that as my solution. No more HDMI to the tv which isolates the two. If I need the OSD, I'll reach back and plug it in temporarily.
As a final thought, I observed the tv has a 2-prong plug (non-grounded) and the receiver has 3 (grounded). In my research, floating vs grounded equipment can do these things. Hope that helps someone in the future.
I'll still keep my eyes open for other solutions going forward. I prefer to minimize adding power cables unless absolutely necessary.
Thanks, all!
