Speaker Noise Problem from Cable TV Signal

When I connect the TV or DVD output to my amp., there is a "wowo' noise from the speakers, even I turn the volume to zero. But when I disconnect the cable TV signal source from the TV or DVD, the speaker noise is disappeared.

Anyone knows how to make good this problem please inform me.

Thanks a lot!!

I have this problem before, after adding a cable tv antenna isolation transformer and the problem solved.

http://www.jensen-transformers.com/iso_vid.html
Model VRD-1FF

Thanks!

Where to buy and what is the price? I have asked around in Apliu Street, still cannot find this product.

Anyone knows where to buy or other items with similar function?  

Anyone has the solution?