Preamplifier

From Free net encyclopedia

A preamplifier (preamp) is an amplifier which precedes another amplifier to prepare an electronic signal for further amplification or processing.

1 Description
2 Examples
3 See also
4 External links

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Description

In general, the job of a preamp is to amplify a low level, possibly high impedance, signal from a microphone or pickup or other transducer to line level. 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 (attenuation), 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 but no significant current. The power amplifier provides the high 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 microphones and electric basses.

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Examples

the integrated preamplifier in a foil electret microphone.
the first stages of an instrument amplifier.
an audio mixing desk.
a masthead amplifier used with television receiver antenna or a satellite receiver dish.

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