Phono input

The phono input is a set of RCA input jacks, usually behind a stereo receiver to which a phonograph or turntable is attached. Modern phonograph needles and phono cartridges output a very low level signal, which is input to the receiver then amplified and equalized.

Phonograph recordings are made with high frequencies boosted. This reduces background noise, including clicks or pops, and also conserves the amount of physical space needed for each groove, by reducing the size of the larger low-frequency undulations. During playback the high frequencies are rescaled to their original level. This is accomplished in the amplifier with a "PHONO" input that incorporates standardized RIAA equalization circuitry.

While in the 1980s even some larger boombox radios had phono inputs, by 2006, only very sophisticated and expensive stereo receivers retained the PHONO input since most users were expected to use digital music formats such as CD or satellite radio. Some newer turntables include built-in amplifiers to produce line-level outputs, devices are available from internet sources that perform this conversion for use with computers, and used amplifiers and receivers are inexpensive.