Axiom Home Page Forums General Discussion Technical Questions Sub hum won't go away

Need some additional troubleshooting steps as the standard ones aren't working. Unless I'm doing something wrong, which is very possible.

My system had been playing for several hours when the sub started humming very loudly. I shut everything down (switching off the power on the EP500) thinking it may have gotten hot or something. So, I waited an hour or so and switched the 500 back on before turning on the revceiver. The 500 started back with the hum. Ground loop issue? I unplugged the line in on the 500 and it still hummed. I then moved the 500 plug (all components are plugged into a Tripplite HT10DBS)to a different circuit. Still she hums. This is with the line in disconnected from the sub. I then disconnected the incoming cable connection from the HT10DBS. It feeds into this before it feeds into the cable box. Still she hums. I then disconnected the outgoing cable from the HT10DBS that actually feeds the cable box. So, incoming is disconnected from the HT10DBS and the outgoing is disconnected. The line in on the sub is disconnected and the plug is on a different circuit via a construction grade extension cord. I even tried using a two prong plug to eliminate the ground prong. No dice.

Any suggestions? I was planning to head to the store to get an isolator, but if the cable is disconnected from the equipment and it's still humming, would it make a difference?

This really blows as I was planning to watch Miami Vice the movie tonight.

All suggestions are appreciated.

Edit: Meant to add that I also removed the chasis ground on the back of the 500 and it still hums. Just to clarify, there is nothing connected to the 500 during these tests.
Stymie