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Preamplifier
From Wikipedia, the free encyclopedia
A preamplifier (preamp) is an electronic amplifier which precedes another amplifier to prepare an electronic signal for further amplification or processing.
In general, the function of a preamp is to amplify a low level signal 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.
- 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.
- The circuit inside of a hard drive connected to the magnetic heads or the circuit inside of CD/DVD drive which connects to the photodiodes.