Every installation technician has faced it or soon will - the dreaded humming from the speakers, a telltale sign of a ground loop. Ground loops are caused by voltage potential differences at the ground point on your equipment. Voltages in the range of microvolts up to millivolts or higher can cause ground loops.The isolation transformer easily connects into your audio/video system and breaks the ground path through cables between components. Start at the component last installed before the ground loop was discovered, and connect the isolation transformer at different ends of the audio/video cable until the ground loop is gone.