Wow. There are so many variables. Yet another reason why listening impressions are so person and location specific.

This one I definitely didn't see coming, although had I thought about it carefully, I would have realized there was a potential for a potential.

My wife (who doesn't understand me) thinks it is nuts to try to get rid of a hum that was only audible if (a) no music or sound track is being played, and (b) can only be heard if you stick your ear within 12" of the sub. I, however, take the approach that if you can hear a noise, and it is possible to eliminate it, you should eliminate it, no matter how minor. Presumably these things are additive. I also treat it as a symptom of a larger problem -- lack of isolation, which is very easy to have happen if, say, you use your TV as a monitor (or any other monitor, probably), or share a compoenet like a sub, or integrate a two-channel system with a home theatre system.

I had a similar problem. When my cable and tv were off and the input set for hearing the tv on my preamp, there was a buzz coming through my speakers. It wasn't present when input set to DAC. When I disconnected the coax from the wall outlet, no buzz, so I knew it was aground loop issue. With the upgrade to my new amp, there is no buzz! BUT while installing the new amp, I had power off to everything initially, and when I turned the amp on, there was an almost inaudible hum coming from the sub, which went away when I turned it on. My audio guys said the Ayre amp is grounded differently, therefore eliminated the buzz and that with it, the sub needs to be grounded to the chassis. I wonder if that is the case now, upon hearing your issue, but either way, I suppose the isolator is a good thing to have anyways. I haven't grounded the sub yet because the screws on the amp require a special tool and the guys needed to dig it up for me to borrow! Although I don't hear the hum with the sub on, I still want to fix the issue.

Bill, I have been thinking about this myself lately. I have been considering integrating some movie playback into my system now that I own a TV (which the mini is plugged into) but could not remember how to tackle this problem oft talked about and discussed with regards to the grounding and hum issues when integrating a TV and Cable Box into the system.

I have a separate 5.1 receiver, etc for the TV. I noticed the other day that when I have Apple's ATV2 displaying the menu, I can hear a very faint noise associated with the intensity of the lighting from the TV as it illuminates the menu items. (I don't think it has to do with the ATV2 itself, but rather simply that the menu has no sound and depending where you are, you get different amounts of illumination.) The noise gets a bit louder when there are lots of items on the black background, and softer when there are fewer items.