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(1) In the hi-fi stereo and home theater worlds, a preamplifier accepts signals from audio and video sources and feeds them to the amplifier and screen. For details, see preamp.

(2) An electronic device that boosts signals to a certain level, which may be further amplified. Preamplifiers are used in fields such as test and measurement, optical detection and audio engineering.


(PRE AMPlifier) 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 also includes the volume control.

There's Always a Preamp
In most high-end systems, the preamp and amplifier are separate components. In all other systems, from the least expensive to very high quality, the preamp and amplifier reside in the same unit, called the "receiver" for stereo systems or "A/V receiver" for home theaters. Receivers typically include an FM tuner; however, a combined preamp/amplifier without a tuner for two-channel stereo only is called an "integrated amplifier."

Stereo Preamps
A preamp used for high-fidelity audio supports two audio channels (stereo) and switches between several audio inputs such as an FM tuner and CD player. It 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 or monitor. See D/A preamp and surround sound.

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