Solution to a ground loop problem

I had the same problem you have and I solved it with the Mondial Magic Brick as Dollysowner did.

I gave away my Mondial Magic Brick when my ground loop was cured. The Brick had problems with the DMX signals on my cable.

Kal

Problem solved! Twofold solution: Replaced the grounding cable at the cable box which solved 50% of the problem and then I stopped by a local highend AV installer and for $5 they gave me a DTIS IS-07 Isolation XFMR 100KHz-IGHz which is an adapter which goes between the cable box and the cable. No hum. Sound like a solution? What do you think?

The Jensen isolator worked for me as well, I got one from a parts site for $30