Radial Engineering MIX2:1

sum the stereo outputs of a console, recording interface, or portable playback device down to mono. You can also combine two separate signals, matching the input levels between them. Inputs can be accessed via XLR or ¼" connectors, allowing you to use balanced or unbalanced sources. Each input features an on/off switch, variable level control, and a ground lift to prevent buzz and hum, should the inputs come from two separately powered sources. Input-2 also has a polarity reverse switch to eliminate cancellation if the two signals are out of phase. Should level adjustments be unnecessary or unwanted, a level control bypass switch is available to defeat both level controls. The MIX2:1 maintains the integrity of your audio quality, with minimal insertion loss, no phase shift, and completely passive summing.