I realize this audio-related issue might not be appropriate for the Stereophile crowd, but here goes nothing, anyway....
In the "Extreme Snake Oil" thread, I mentioned an observation I recently experimented with (but discovered some 10 months ago), while I was busy installing a light switch (dimmer style, but it doesn't matter). The observation being that my audio sound is affected by how the light switch is wired to the house wiring. I'm not speaking in the traditional sense of the Romex leading to the electrical outlets. I'm talking about the fact that a standard light switch (NA 120v) can be connected either of 2 ways to the house wiring; ie. red -> black or red -> red. It will normally work either way, as far as the light coming on is concerned.
But one way always seems to sound better than the other way. The difference in sound is similar to traditional means of polarity reversal in an audio system; ie. switching speaker wires. It's probably best heard on stuff like piano music, or horns. One way has clarity and musicality to it, the other way is less distinct. (I wont say which connection I think is better, lest I be accused of introducing expectation bias). If you can't hear polarity differences, or simply think they don't exist, it's a safe bet you won't be able to lock in to this one either. To me however, it's an important difference. It could mean the difference between an involving system, and one that isn't. When I say it affects audio sound, I mean any audio sound. Which unfortunately kills any theories that it is somehow affecting the line that eventually leads to your audio gear. I say this because I have always used an mp3 player to test the effect (it's just more convenient for me, because I can test without leaving the location of the switch).
I'm wondering if anyone has made a similar observation (although I doubt it), or is willing to repeat the experiment? (If you do, **make sure you turn off the power, before you start!**) I've only tried this on two or three occasions myself, but I'm pretty convinced it's a consistent effect (not imaginary). I plan to study it further in the future, when I get more serious about it, but if anyone else has any input, that'd be great.
BTW, I know many would be thinking this and some of them would be eager to tell me this, so yes, I already know there isn't a conventional explanation for it. That doesn't mean it isn't happening.