I have the same thing with my new 4.1's, this is just using the wire that came with them. it is kindof a buzzing/ringing sound coming from my front right sat.
If i turn the power switch on the speaker off, or even turn off my computer, the buzzing noise is still there, Even if i completely disconnect the pre-amp from the subwoofer the noise is still there.
btw the volume of this noise doesnt change when i increase the speaker volume.
My current theory is that it is either just electrical noise from the outlet, or it is being created by the amp itself. I have a normal stereo in a different room that doesnt get this noise, but who knows why, maybe it's power supply just has better electrical filters or something.
Anyways i can only hear this sound if i turn ogg my computer or put my ear up real close to the sat. I dont hear it during normal use, so i'm not too worried about it, but if anyone has any ideas what causes it I would be interested out of curiousity