I posted this response in the "Subwoofers, Bass, and Transducers" forum, http://www.avsforum.com/avs-vb/showt...9#post17154999
but it should be part of this sticky as knowledge base info.
Originally Posted by NCARalph
I recently redid my AV system to use pretty much all HDMI cables and removed some obsolete components. The result was a very annoying hum.
After some isolation, I determined it was originating in the Comcast cable feed and being distributed by the HDMI cables. Putting in a 3 to 2 prong plug to lift the ground from TV (the only component with a 3 prong plug) helped but didn't fix the problem, plus running completely without a ground worried me.
So I got a Jensen Transformers VRD-1FF on ebay, plugged it in, and POOF! the hum completely went away, even at high volume and no input. This has had no impact on the quality of the cable video including the HD channels. I don't use view on demand or any of the premium channels so I can't comment on those.
Worked for me.
NB - Read and follow the directions that come with it!
I had same problem, the cable people did a crappy job with grounding using cheap clamp, it had I think a bi-metallic corrosion going also as well. (wiggly clamp)
Before showing cable install job:
I took the clamp off, went to HD, bought 6' copper wire, attached to inside home copper pipe, actually next to where the 200A main also had a ground wire attached.
Copper wire going into basement shown:
To make matters a little more complicated, my outside faucets are "isolated" and not really connected to my inside pipes, due to my whole home EcoSmarte system, which uses various plastic/assy stuf for flowmeters, electrodes, etc.
So I connected a jumper wire from my inside pipes to my outside pipes, just to have them on the same ground plane.
This pict shows my whole home H20 system, kinda complicated but great H20 for whole home.
I also made sure the OTA antenna ground plane was same datum.
Here is in construction phase showing the home 2 ground rods.
Here is the OTA antenna being correctly grounded to the red circled one, it is visible just past hot tub cement pad.
Showing OTA copper wire on LH going around the corner under deck, while the antenna lighting rod is grounded next to the elect meters.
So, when solving ground loop issues you have to totally trace/follow your elect system and cable/sat/OTA/etc ground points.
For me, no more ground loop issue.
Maybe $12 max.