Hi, and thanks to all who have posted responses; much appreciated. Since making the OP, I have done a little experiment to determine whether I have a noise problem -- practical,not theoretical. Here is what I did. With my playback source on pause,I turned up the volume on my amp (Cambridge 840A v.2) and listened for noise. At -0 db,I could clearly hear some fuzz; but I usually listen at -30dB. At -20 dB, I had to be within 5 feet of a speaker to hear any noise. At -30 db, I couldn't hear any noise even when I pressed my ear directly against the speaker; I think this means I have a 0dB noise floor at my usual listening station ("The Con" is a good 12 feet from the speakers). I am pretty well satisfied that any noise in my system, AC-induced or otherwise, is a theoretical concern, at least with regard to audible interference/background noise on playback. Now, as to effects on soundstaging or other effects impacted by line noise, I suspect there is more to be said. But as far as creating/assuring a dead-black, 0dB background ... I think I'm actually already there. Thoughts?
Power Conditioning: How Do You Know You Need It?
Like many, I have been considering whether to purchase a power conditioner (e.g., PS Audio Power Plant Premier), that sort of solution for electric noise. Accepting the premise that cleaning the AC will improve the sound, how do I know whether I actually have a problem that needs to be solved? That is, how do I determine whether the AC coming out of my wall outlets is actually dirty, before dropping two large on a device that I might not actually need? Living in Chicago, I would *assume* my electricity is as dirty as it gets, but how would I *prove* that before investing in a power conditioner? And I suspect the real issue may be noise occurring *inside* my home, like my WiFi router, energy-saving compact fluorescent lights, the 6-foot tall Tesla coil I keep running 24/7 "just in case" next to the hamster cage, etc.