If this is a ground loop hum created within your own system, it should go away if you float all plugs in your system EXCEPT one. You should have one component connected to ground; your interconnects ensure that there is a path back to ground for your remaining components.
If this doesn't do it, then your problem lies elsewhere. Is your system tied to video that includes cable? Cable boxes are notorious for introducing ground loop hum into audio circuits, if they are on the same line.
A final thought - flourescent lighting, electric motors, radio transmitters will create strong interference fields that will be picked up by unshielded wire and interconnects acting like antennas.
If this doesn't do it, then your problem lies elsewhere. Is your system tied to video that includes cable? Cable boxes are notorious for introducing ground loop hum into audio circuits, if they are on the same line.
A final thought - flourescent lighting, electric motors, radio transmitters will create strong interference fields that will be picked up by unshielded wire and interconnects acting like antennas.