[email protected] is correct in pointing you towards gounding rather than a problem with 3 phase power, I,d give up my left arm to have 3 phase power in my home. Proper grounding is a big factor with hum and noise problems, especially with pro and high end audio equipment that usually employ 3 conductor grounded power cords and balanced inputs/outputs. I have installed sound systems in a few local bars and nightclubs in the past. One particular club I installed a sound system in, had an intermittant hum/static noise problem. I found that the problem was caused by the electrical sub-panel, feeding the sound system, did not have the neutral/ground buss bonded to earth ground. There was more than a 5VAC difference between the ground buss in the panel and a nearby water pipe due to the fact that the earth ground connection to the buss in the panel was being made through the current carrying neutral line. Most sub-panels in commercial buildings and service panels found in homes have the neutral connections and earth ground connections to the branch circuits connected to the same buss bar in the service panel. For proper gounding this buss bar must be tied to both the neutral line coming into building (or the main switch gear feeding a multiple sub-panel arrangement) and the ground line running out to the grounding stake outside the building, the grounding stake line is usually tied to the service panel box and a bonding screw or wire is used to connect the box to the buss bar. A few things you should check if you are having hum and noise problems are, make sure that you have a good connection to the grounding stake outside and that at least 30 inches of the stake is below the ground level. If you have an older home where the wiring is fed through greenfield flexible conduit, run a seperate ground wire between the outlets feeding power to your system and the service panel. Flexible conduit is a poor grounding conductor, especially as it ages and oxidizes between the flex joints. One last thing to try is, in the service panel, move all of the neutral lines feeding the branch circuits to the portion of the neutral/ground buss bar between to the main neutral line feeding the panel and the bonding screw/wire, and move all the branch circuit earthground wires to the other side of the bonding screw/wire. If you are not familiar with electrical wiring safty and codes it would be best to hire an electrician to do this. Hope this helps.
