RFI from steel TV bracket?

Last TV was plasma. No hum.
This TV is LCD......hum.
But it hums with the TV completely unplugged so I don't see how it can be the source?

Ground loop from your cable tv or sat box. Unhook the coax cable from the source tv direct/cable box or sat and turn everything else back on and take a listen. Tom

Yes I unplugged the TV and also tried it in different GPOs.....even a power conditioner. I even disconnected the 'sound-out' of the TV from the preamp. Hum still there.
11-13-11: Halcro

Want to rule in or rule out 100% the hum is being caused from the metal bracket? Take the TV down from the metal TV bracket, set the TV in the middle of the room, and then check for hum...

If I understand this you just installed the TV mount onthe wall. Is there any chance a screw cut into your Romex in the wall and is hitting a grownd wire? I would say try removing a screw at a time and check for the hum. It just odd that an LED Tv is doing this or that the metal mount is causing it.

I unhooked the cables from the cable TV......no change.
I then suspected the 2 metre long Cardas cable interconnects running on the shelf behind the TV and just under the steel brackets and plate.
The right-hand interconnect runs right across this 'field' before dropping down to connect with the speaker....whilst the left channel interconnect runs for only a foot before dropping down.
The left speaker only emits a light buzzing whilst the right speaker has the definite 'hum'.
So I wrapped both interconnects in aluminium foil and this reduced the level of the hum and buzz.

Not knowing much about electricity.......is it possible for the steel bracket combining with all the power outlets directly below it, to create an electro-magnetic field which the long runs of unshielded interconnects then acts as 'antennae' for the RFI/EMI?

If this is indeed the problem.......would going to fully balanced XLR interconnects, solve it?