Short for “microphone input.” An input designed to accept microphone level signals. A microphone input is typically low impedance and balanced, on XLR connectors. However, TRS connectors may also be used, and in some cases, a microphone input may be on a 1/4-inch TS connector and operate unbalanced with higher impedance.
Microphone inputs often feature phantom power, a pad, a low-cut filter, phase invert, and other features.

