If you have an ep500 or and ep600 I would loosen the ground screw on the back first and see if that helps.
If that doesn't work I would purchase the axiom ground isolator.
It is $48 and eliminated my subwoofer hum completely. I even talked my cable company into paying for it after being escalated to a manager.
If you use resistors and rig up something yourself you may fix the problem but will probably lose you picture if you have any HD or digital channels.
more discussion here:
http://www.axiomaudio.com/boards/ubbthreads.php?ubb=showflat&Number=187122&fpart=1
