Cable TV receiver induced hum into system

I'm away from home. I'll check which ground makes the difference. I've been looking on line for a Mondial Magic and don't find one. Any ideas?

http://www.amusicdirect.com/products/detail.asp?sku=AMONDBOX
Google has many other hits for "Mondial Magic".
If you want to be sure this is the problem, a cheap way would be to go to radio shack, and buy 2 75-300 ohm baluns. The kind you used to use to hook up cable tv to an old tv with just antenna screws. Take the 2 baluns, and hook them together by the wires. Either clip off the spades and just twist and tape for this experiement, or you could just use screws and nuts.
Now plug your cable feed into one end, and run a new cable from the other end to your cable box. If this eliminates the hum, you have found the source of your problem. Then you might want to spend the money on the Mondial.
John

Here is a link to the baluns from Radio Shack:
http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F003%5F010%5F001%5F000&product%5Fid=15%2D1140

I'm having my youngest son do the test today.

I'll know soon.

Thanks again.

Audio Advisor sells the Mondial Magic's. If you find that you need one, look under "Manufacturers" on their website for Mondial and you will find an isolation transformer and an isolation transformer/splitter. I used the transformer/splitter and sent one output to my HT, and the other went to every other TV in my house (using less expensive splitters as needed). Hope this helps.