The PHE400 Mini 2-Channel Hum Eliminator from Pyle Pro is designed to completely eliminate 60 Hz AC hum caused by ground loops. It features 1/4" TRS and XLR inputs and outputs on each of its two channels.
AC hum and noise are almost always caused by a loop antenna effect across signal lines between pieces of gear, or by long unbalanced cable runs—since unbalanced lines are more susceptible to picking up electrical noise and RF interference. This unit breaks the ground loop, eliminating the possibility of signal lines picking up AC hum and noise and also converts unbalanced signals to true balanced signals. In addition, the PHE400 automatically translates signal voltages to match the differences in ground potentials.
utilizing 11:1 isolation transformers to break loop antenna