API Audio 3124MV, 4-Channel Microphone, Instrument And Line Preamplifier, Classic API circuit design, API 2520 OP amplifier, Switchable per channel: 3:1 output transformer selection, +48V phantom power, -20 dB pad, polarity, LED meter and adjustable gain and output volume per each channel, Stereo panner with a level control, Aux send (post fader), 4 Inputs: XLR, 4 Hi-Z inputs: 6.3 mm jack, 4 Outputs: XLR, Construction: 19"" / 1U