The HE-2 from Ebtech is a two-channel "Hum Eliminator" box, designed to eliminate 60Hz hum caused by ground loops. Almost all 60Hz AC hum is caused by ground loops that act like radio antennae (loop antennae). The Hum Eliminator completely eliminates this by breaking the ground loop, making it impossible for the signal lines to pick up the AC hum and noise in the first place.
Unbalanced lines are more susceptible to picking up electrical noise and RF interference than balanced lines - the longer the unbalanced cable, the greater the chance of a problem. Using the HE-2 to connect two pieces of equipment is one of the most cost-effective ways to convert between unbalanced signals and true balanced signals. The unit features 1/4" TRS phone inputs and outputs on both channels.