So there are three explanations, none of which are mutually exclusive:
1. My hearing is terrible.
2. My gear is properly designed and doesn't pass through power line noise.
3. Power conditioners generally don't do anything to improve sound.
When I had my hearing tested last December, I was found to have acute hearing (equivalent to that of a small child except for a slight 4 kHz notch in my left ear), so explanation 1 is out.
Explanation 2 is a good bet, as I've unloaded all the finicky audiophile stuff I used to own.
Explanation 3 is also a good bet. (Ok, ok, some power conditioners do something, and when I engineered recordings, I used an immense Furman 20A voltage regulator to power mic preamps and A/D converter.)
Figure out how to do some blind tests of this stuff, and then please let us know how consistently you perceive the differences. No peeking!