I have had the hum for some time - just ignoring it. I notice it most from my QS8's during normal listening when there is a quiet moment like the breaks between commercials. Alan's article leans heavily towards the sub being the culprit. I'll do the search, do some reading, and do some checking tonight to see what I can come up with. Thanks for the responses.

"A fanatic is someone who can't change his mind and won't change the subject" Churchill