The
ground loop isolator is for the cable feed into the amp/set top converter etc. I suspect there is a poor ground for your cable/house and it is manifesting itself through the various RCA connections going into the amp and the analog connections on the player and making it's way back to the sub.
Try Zimm's idea, also try plugging the player into the same outlet as the rest of the system for a common ground, if all that fails, you have nothing to lose buy purchasing the isolator and giving it a try.
