That dreaded hum

I had the same problem. This was my solution. Went to Radio Shack and bought a small plastic box, 2 switches, 4 RCA jacks and frabricated a switch box. Toggle switches turn audio signal off/on from TV's audio "Output" jacks. Needed one extra set of interconnects. Works perfectly. The reason I did it this way was because my cable reception is excellent and I didn't want to take any chances messing up the video signal.

As noted above, the Mondial device is still available, and there are other similar solutions.

Before doing anything else, I would suggest to check to ensure that the installed cable connection coming into your house is grounded correctly. Many older installations are not. If you watch current cable installation techs, (at least Comcast here in Washington) they are pretty careful to be sure to mount a gounding adaptor at the house entrance (either pass-thru or tee fitting) that has a solid ground lug connection that is then bonded to the household ground system. In many cases, this will eliminate the ground loop all by itself.

audioholics.com has an article on the subject. they suggest a product from jensen @ $60. they have tested a few products and this is the one that apparently does not filter or degrade the signal coming through it. i plan on purchasing this item. good luck, d.

Many thanks to all that have responded. The radioshack fix may be the best bang for the buck. Someone else had told me about the 75 to 300 ohm setup. I will try this first. Good listening.

Another approach I've used successfully: attach a ground lead to the coaxial shield at the point where it connects to your equipment. Wrap the bared end of wire around the coax a few times & cable-tie it securely, or use a small hose clamp. The other end of the ground wire connects obviously to ground: use your AC wall outlet's plate-mounting screw, or perhaps a handy ground post on your preamp, etc.
Realize that inserting back-to-back baluns results in several dB of RF signal loss: check your picture quality before & after to ensure that it hasn't degraded.