Hi,

In my humble opinion a power conditioner has nothing to do with this problem. It is possible that the tv and radio cables aren't properly screened so replacing it with better quality ones (preferable with extra foil for screening) won't harm. Secondally, try to put the front speakers on the rear channels. If the weird sound is gone than you will have proof that the above can help.
Bram

Quote:

... my rear speaker cable runs right along side the cable for the cable T.V. Could this be the problem? Should I try to separate the cables?

Seabass,

Listen to Bram. Also, try using quad shielded coax and, if possible, don't run power cords and RF cable parallel in close proximaty to one another