A phono preamp, also known as a phono stage, is an audio component that amplifies the signal from a turntable to a level that allows it to be connected to a sound system the same way as any other audio source. The signal coming out of the cartridge/stylus on a turntable is around 1,000 times lower than the signal coming from a CD player or a streaming device, so it needs to be boosted to be heard through speakers or a stereo system. A phono preamp also applies the RIAA equalization curve to the signal, reverting it back to the shape it was on the original recording.

If a turntable does not have a built-in preamp and an amplifier or receiver does not have an input labeled "phono," then a separate phono preamp is needed. However, some vintage amplifiers or A/V receivers have a built-in preamp, which can be identified by a set of left and right input connections labeled "phono" with a ground screw next to them.

The quality of a phono preamp can have a significant effect on the overall sound quality of a system, and dedicated phono stages are fine-tuned to reproduce the warm sound of vinyl, free from hiss or bearing rumble. There are two types of phono preamps: those designed to work with moving magnetic cartridges (MM) and those designed to work with moving coil cartridge types (MC) . Some preamps cater to both designs, with a simple switch that adjusts the preamp accordingly.

In summary, a phono preamp is a necessary component for playing vinyl records on a turntable and amplifying the signal to a level that can be played properly through a sound system. It also applies the RIAA equalization curve to the signal. Vintage amplifiers or A/V receivers may have a built-in preamp, and there are two types of phono preamps: those designed to work with moving magnetic cartridges (MM) and those designed to work with moving coil cartridge types (MC).