A preamplifier (preamp) is an electronic amplifier which precedes another amplifier to prepare an electronic signal for further amplification or processing. Description In general, the function of a preamp is to amplify a low level signal (possibly at high impedance) to line-level. A list of common sources would include a pickup, microphone, turntable or other transducer. Equalization and tone control may also be applied. In a home audio system, the term 'preamplifier' may sometimes be used to describe equipment which merely switches between different line level sources and applies a volume control, so that no actual amplification may be involved. In an audio system the second amplifier is typically a power amplifier (power amp). The preamplifier provides voltage gain (about: 10millivolts to 1volt) but no significant current gain. The power amplifier provides the higher current necessary to drive loudspeakers. Preamplifiers may be: •incorporated into the housing or chassis of the amplifier they feed
•in a separate housing
•mounted in other pieces of equipment, such as turntables, microphones and electric basses.
•close to the signal source, remote from the next amplifier -- eg: beside hi-fi system, then feeding into a computer in the home office. Examples •the integrated preamplifier in a foil electret microphone.
•the first stages of an instrument amplifier.
•a stand-alone unit for use in live music and recording studio applications.
•as part of a stand-alone channel strip or channel strip built into an audio mixing desk.
•a masthead amplifier used with television receiver antenna or a satellite receiver dish. http://www.answers.com/preamplifier?cat=technology