Hi Stu.D,
If you have a cable box or satellite receiver hooked up to your system it might be the source of your problem. Disconnect the RG6 cable feeding your cable/satellite box from the wall outlet. If the hum dies away then it is a ground loop issue. If you remove the sub cable from your EP600 does the hum stop?
Here is a link for helping you trouble shooting it -
EP600 Trouble Shooting Guide Don't hesitate to dial Axiom's toll free number (866-244-8796) if you need further assistance.
Good luck !
