Ground loop hum - 2.1 Active Monitors- CONFUSED FRUSTRATED

[CabreeToe]

I made a christmas birthday present purchase for my wife. She likes her turntables and wanted some small speakers for here office. I got some Samson S5a and S88 sub package. To connect to her dj mixer with out the need for an amp. The samson system appealed to me cause of the un-balanced input for the dj mixer as well as XLR inputs for a later upgrade (maybe)


Anyway, go the things home. Unpacked, hooked up, then when I powered it on I was almost blown across the room when I hit the switch for the sub. A very loud solid Sine-wave like tone. Possibly at 60Hz. I stared checking different outlets, powerstips, everything. So its just the unbalanced input on the sub. Cause, if its powered on its fine. but when I connect even one RCA cable into either of the inputs I get that hard heavy hum. the small satallite speakers down't seem to have that problem. Nor do my personal monitors. If I connect 2 unbalanced rca cables into the input and touch the other two ends together it cancels out the noise. So its a ground loop from the input Right? I dunno.

My wife tries to take it back and they test it in store and everythings peachy. Granted she couldn't remember what the problem I said was and they may or may not have used the un-balanced inputs. I suspect they may have tested it on the balanced XLR.

I tried different power and u-balanced audio cables. And tried pluging in to every power outlet in my house including the True-Online UPS that should give me the cleanest power I have.

Whats the deal? Are they correct.(the store jerks that fucked with my wife cause shes a chick) Are the speakers fine and its just my shitty electric wiring in my house that the sub hates or. Can a Sub be defective and have a gound loop happen inside it?

Any help would be great! Cause the sound I could hear above the hum of the sub wasn't half bad.

thanks much