Diki/Dave: Thank you so much for the suggestion and the background on potential causes. Dave, the house-systems electronics are across the room from me so I can not plug into the same circuit.

I did a quick search of hum eliminators at Sweetwater and elsewhere.
http://www.sweetwater.com/store/search.php?s=hum+eliminator&tt=1

Any thoughts on the ART DTI vs the Ebtech? The ART DTI is a dual-channel device like the Ebtech, however, the ART DTI allows for 1/4", XLR, and RCA. Seems like a more versatile device.

Any reason not to get the ART DTI instead of the Ebtech?