Try turning down your sub volume -5 db and see what happens...see if the humming is related to the volume setting on the receiver...
When the sub volume is lower, the receiver does add some hum but only at extremely high levels of volume nearly 0 dB on my HK.
This amount of hum is way less than when I crank up the sub volume at normal receiver volume.
I think there it is either AC noise that is passed through or some noise creeping in from the receiver through the rca cable connectors. I need to get an AC filter and Maybe I'll buy the Axiom or Hsu sub cable? But the Monster cable I use now should work fine. it doesn't seem to be interference because I have pulled the receiver out (temporarilly) and moved the sub cable all by itself with 2 feet of space between it and anything else. That did not help at all.
