[BlindHandyMan] ground lop isolator from shlock:

[Tom Fowle]

"Ground loop isolator", This is a stereo cable with RCA plugs on both ends 
comes with 1/8Th inch  adaptor. presumably has two magnetically shielded 
transformers. 
Price $16.99
Catalog #270-054 

They don't give the length but it may help 
Tom Fowle