Audio component that adjusts the volume of an audio signal and performs switching functions between attached input devices and an amplifier or group of amplifiers. The preamplifier's primary task is volume control and source control. It is used to choose between attached components and let only one pass along its signal. It is also used to adjust the balance, the treble and the bass. Balance is the amount of sound put out by one speaker versus another and usually a left versus right stereo pair.

Preamplifiers are available with a wide variety of functions and additions. Many feature built-in tuners. These preamps then also control tuning functions. Most preamplifiers come with a remote control to operate their various functions from a distance. Many preamplifiers now also feature surround sound acting as surround sound processors. These models feature matrixed Dolby Pro-Logic surround sound (sometimes combined with THX certification and its various enhancements). Many newer models also feature Dolby Digital and/or DTS 5.1 digital surround sound formats. Thus the function of the preamplifier is to route a signal from source components to amplifiers (or video to a video display - preamps do not affect the video but just select it and send it on), perform some alteration to the signal when required (as in surround sound, digital surround sound, balance control, etc.), and adjust the volume of the system.

The preamp is in essence the brain of an audio/video system. It has the smarts; the amplifiers have the muscle. Preamplifiers are available in stereo only models as well as surround sound preamp/processor combinations. Look for a preamplifier that has lots of good quality inputs and outputs along with low distortion and an easy-to-use design.

Most of the new generation equipment such as cassette decks, CD players etc come with a pre-amplifier stage that would give out sufficient output to drive the power amplifiers. Hence except in the case of very high end configuration or for studio purposes separate pre-amps are not being used as such.