Try transfering the vibration away from the audio path. If you give the resonance frequency a place to go other than the audio path it will. The most effective unit out there deigned to do this is a Sistrum stand anybody that has heard one will agree. Look it up on the audiopoints website @www.audiopoints.com. However you should still fix the source of the problem. Most times lifting the ground is a simple solution and cheaper than a power conditioner. Still try the rack even if to fix the hum.
