By all means follow the advice given by Mr PTM! That wisdom has been around for as long as I've been in audio/sound reproduction(over 30 years). NOT ALL NOISE IS CONSCIOUSLY AUDIBLE. That's why the differences power conditioners make are sometimes hard to describe: They've removed things that you weren't even aware of. Hum and other noises are are only part of the potential problems. There are magnetic fields around any cable conducting AC signals that can induce voltages/fluctations/distortions in any other cable in close proximity. The various shielding and braiding techniques are good, but none are 100% cures for the possible problems.
