Radial Engineering MIX 2:1 2-Channel Audio Combiner & MixerThe Radial Engineering Mix 2: 1 is a passive mixer that sums two audio signals to a single mono output. It provides individual input knobs to balance the two signals, should one be louder than the other, as well as a polarity switch on input 2, should one of the signals be out of phase. The unit accepts balanced 1 4" and XLR inputs, outputting to a single XLR output. Each input can be switched on or off. This allows you to audition either signal