Definition: preamp

(PREAMPlifier) Meaning "before the amp," the preamp is the primary control unit in a stereo or home theater system. It switches low-level signals from audio and video sources to the audio amplifiers, which boost the preamp output sufficiently to drive the speakers. The preamp always includes the volume control.

There's Always a Preamp
In extremely high-end systems, the preamp and amplifier are separate components (see audiophile). In all other systems, from the least expensive to very high quality, the preamp and amplifier reside in the same unit, which may also have an FM tuner.

When used with video in a home theater, the combined unit is called an "A/V receiver." For audio only, if it has an FM tuner, it is a "stereo receiver." If there is no tuner, it is called an "integrated amplifier" (see A/V receiver, integrated amplifier and stereo receiver).

Stereo Hi-Fi Preamps
A preamp used for high-fidelity audio supports two audio channels (stereo) and switches between audio inputs such as an FM tuner, CD player and digital media player. The preamp also provides RIAA equalization for phonograph turntables (see phono preamp).

A/V Preamps - The "Pre/Pro"
A preamp used for home theaters supports multiple audio channels and the many surround sound processing technologies used in movies. Also called a "pre/pro" (preamp/processor) because of all the audio processing, the preamp switches between both audio and video sources such as a CD player, cable box and Blu-ray player, sending the audio to the speakers and the video to the TV. See D/A preamp and surround sound.

An Unusual Stereo Preamp

This high-end LUMIN P1 is a stereo preamp that supports all digital audio inputs (see S/PDIF). Connected to an amplifier, the P1 is also a music streamer and control center for a stereo home theater (only left and right speakers). There is no phono equalization. (Image courtesy of Pixel Magic Systems, Ltd.)