When I first got the 770, I was getting some ground loop noise and rather than say it's cables or connections right off the bat, I listened for a while to seek variations and try and isolate the cause. Well, I noticed that the A/C and fridge running caused some hum. So, I investigated power conditioners and ended up deciding to try the PS Audio Ultimate Outlet. True to the web-site and other testimonials, I noticed a significant drop in 60Hz hum, to the point that you have to be right up on the speaker to hear it where as before, it was evident from my listening position. I ended up getting the HC 15A version for $325 new. I would recommend this for any of you experiencing ambient noise and looking for a quick fix outside of power regenerators or filters. This unit is a lower class of a filter using a balun to reject noise.

More AC power conditioning products:

http://www.furmansound.com/consumer/ref/

http://www.panamax.com/Products/families.asp?family=1

http://www.monstercable.com/power/lineHomePower.asp

I use the Furman PS-PRO II Power Conditioner/Sequencer with SMP"Series Mode Protection" and Lift "Linear Filtering Technology" with a total of 20 Amp Power Handling built into the unit, everything runs like a charm, no outside noise whatsoever.