I realize this is a well beaten subject but I have a hum present in my Theatre and have not been able to eliminate it.
If I unplug the Sub from the outlet the hum is gone. Plugging the sub into a different circuit/outlet did not remove the hum. Removing the grounding screw from the Amplifier plate on the back of the sub did not help, there is an Axiom audio ground isolator in line for the cable box.
I do not use XLRs for connections.
Am out of ideas!
Any thoughts on how to proceed?

thanks, Jeff
ps- Happy Holidays