(PHONOgraph input) A socket on an amplifier or receiver that accepts signals from an analog turntable. The phono input circuit boosts the signal and provides the RIAA equalization necessary to restore the original sound. See phono preamp and USB turntable.
Even the most sophisticated A/V receivers with myriad digital surround sound processing have a phono input. This is the back panel of Arcam's acclaimed AVR600 audio/video receiver. The MM stands for "moving magnet," a common type of phonograph cartridge.