I think I may have figured out what the issue is -- when I turn the 'Tone In' = 'ON' I hear the hum, on different surround modes (though not all), at most volume levels (HK Receiver basically goes from -80 to +10) so the louder it goes, the worse the hum.

For $HIT$ and giggles, I turned the 'Tone Out' = 'ON' which got rid of the hum, except at really insane levels (i.e. -10 to +10) on the receiver. I also tried different surround modes, here...and had the same effect. No hum. I also tried different surround modes, and did not expperience the hum, below a certain volume, with the Tone Out = ON.

So, I am thinking that it was the 'Tone In' settings, where I had the treble up and the bass low. Don't know why I would be hearing a hum, though? I will try taking the unit out of the protector, and plugging it directly into the wall...and try both tone in and out modes tomorrow (later this morning, when I wake up again)

I will also be contacting HK customer support, and/or Onecall's customer support. Let's see what they have to say. I also sent Brent (at Axiom) an email, and maybe he will shed some light on this issue, as well.

More to follow...when I am able to do some more testing. G'nite.