Joe, I know another A/V component is the culprit, but it's not easy to pinpoint, as I have audio, video, and computer gear all interconnected, and difficult access to most of the non-audio cables. The "cheater plug" on my preamp eliminates the hum, so, for the time being, it would be easiest to just "upgrade" to the Hum X, as long as it doesn't "choke" the power output to my preamp. I've ordered a Hum X, and will see if it degrades system performance in any way.