I'm not suggesting power conditioners don't work- in fact, they may work effectively in eliminating more than what you intended.True
Most of the ac mains "dirty power" found in our houses is caused by devices, equipment, and appliances, found in the home. Including the audio equipment itself.
As for dirty power put back out on the ac mains by the audio equipment, that is why more than one dedicated branch circuit is used.
YMMV.