Warm Audio WA-412, 4-Channel Microphone and Instrument Amplifier, 100% discrete, transformer-balanced circuit, Altran USA Custom wrapped premium input and output transformers, X520 operational amplifiers in each channel (exchangeable if required, as plugged on base), 65 dB gain, Transmitter-balanced XLR and active instrument inputs, Transformer-balanced XLR and jack outputs, TONE switch changes the impedance of the microphone and instrument preamp from 600 to 150 ohms, -20 dB pad (affects microphone and instrument preamps), +48 V phantom power, LED metering, Output-Trim control for precise volume control and saturation effects, Internal power supply, Format: 19 ""/ 1U