Ok here we go.. I've had this issue for awhile now and I'm finally getting super annoyed with it. I have a desk with a built in rack. The only pieces I use are my Furman power conditioner, presonus fire studio project and an Alesis RA-150 Amplifier for my monitors. Almost anytime i want to plug in my headphones I have to touch the connector to something metal first (i can hear an audible shock) before i plug it in to the headphone jack of the Presonus. If I don't do this.. the Presonus will get a shock or something and the LED clip lights will all go off. I then have to turn off the unit and restart it. How can I avoid this. Is having a rug causing this? There is also a slight hum if i crank the gain knobs of the headphones or monitor output of the Presonus. Do I have a ground loop somewhere?