Preamplifier


Preamplifier
An example of a typical high-end stereo preamplifier.

A preamplifier (preamp) is an electronic amplifier that prepares a small electrical signal for further amplification or processing. A preamplifier is often placed close to the sensor to reduce the effects of noise and interference. It is used to boost the signal strength to drive the cable to the main instrument without significantly degrading the signal-to-noise ratio (SNR). The noise performance of a preamplifier is critical; according to Friss' formula, when the gain of the preamplifier is high, the SNR of the final signal is determined by the SNR of the input signal and the noise figure of the preamplifier.

Contents

Description

In general, the function of a preamplifier is to amplify a low-level signal to line-level. A list of common low-level signal sources would include a pickup, microphone, turntable or other transducers. 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 (e.g. from 10 millivolts to 1 volt) 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 within or near the signal source, such as a turntable, microphone or musical instrument.

Examples

See also

External links


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • preamplifier — (n.) 1935, from PRE (Cf. pre ) + AMPLIFIER (Cf. amplifier). Shortened form pre amp is attested from 1957 …   Etymology dictionary

  • preamplifier — [prē am′plə fī΄ər] n. in a radio, phonograph, etc., an auxiliary amplifier for boosting the voltage of a weak signal before it reaches the input of the main amplifier …   English World dictionary

  • preamplifier — priešstiprintuvis statusas T sritis automatika atitikmenys: angl. booster amplifier; preamplifier vok. Vorverstärker, m rus. предусилитель, m pranc. préamplificateur, m …   Automatikos terminų žodynas

  • preamplifier — priešstiprintuvis statusas T sritis fizika atitikmenys: angl. head amplifier; preamplifier vok. Vorverstärker, m rus. предварительный усилитель, m; предусилитель, m pranc. préamplificateur, m …   Fizikos terminų žodynas

  • preamplifier — noun Date: 1935 an amplifier designed to amplify extremely weak electrical signals before they are fed to additional amplifier circuits …   New Collegiate Dictionary

  • preamplifier — /pree am pleuh fuy euhr/, n. a device in the amplifier circuit of a radio or phonograph that increases the strength of a weak signal for detection and further amplification. [1930 35; PRE + AMPLIFIER] * * * …   Universalium

  • preamplifier — noun a voltage amplifier for amplifying a low level input signal; its output is the input to a higher level amplifier …   Wiktionary

  • preamplifier — n. device designed to strengthen very weak signals before they pass through the regular amplifier …   English contemporary dictionary

  • preamplifier — noun an electronic device that amplifies a very weak signal and transmits it to a main amplifier …   English new terms dictionary

  • preamplifier — pre·amplifier …   English syllables