Editing Preamplifier

{{Short description|Electronic amplifier that converts weak signal into strong signal}}
{{Redirect|Preamp|the device used in professional audio|Microphone preamplifier}}
{{more citations needed|date=February 2024}}

[[Image:Musicfirstaudioclassicpreamplifier.jpg|thumb|right|An example of a typical high-end [[Stereophonic sound|stereo]] preamplifier]]

A '''preamplifier''', also known as a '''preamp''',  is an [[electronic amplifier]] that converts a weak [[electrical signal]] into an output signal strong enough to be noise-tolerant and strong enough for further processing, or for sending to a [[power amplifier]] and a [[loudspeaker]].<ref>{{Merriam-Webster|preamplifier}}</ref> Without this, the final signal would be noisy or distorted. They are typically used to amplify signals from analog sensors such as [[microphone]]s and [[pickup (guitar)|pickups]].<ref name="PCMAG v825">{{cite web | title=Definition of preamp | website=PCMAG | url=https://www.pcmag.com/encyclopedia/term/preamp}}</ref> Because of this, the preamplifier is often placed close to the [[sensor]] to reduce the effects of [[Noise (electronics)|noise]] and [[Electromagnetic interference|interference]].

==Description==
An ideal preamp will be linear (have a constant [[Gain (electronics)|gain]] through its operating range) and have high [[input impedance]] (requiring only a minimal amount of current to sense the input signal) and low [[output impedance]] (when current is drawn from the output there is minimal change in the output voltage).  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 [[Friis formulas for noise|Friis's 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.

Three basic types of preamplifiers are available:
* current-sensitive preamplifier
* [[parasitic capacitance|parasitic-capacitance]] preamplifier
* [[charge amplifier|charge-sensitive preamplifier]].

==Audio systems==
In an audio system, they are typically used to amplify signals from analog sensors to [[line level]]. The second amplifier is typically a [[power amplifier]] (power amp).  The preamplifier provides [[voltage]] gain (e.g., from 10 mV to 1 V) but no significant [[Electric current|current]] gain. The power amplifier provides the higher current necessary to drive [[loudspeaker]]s. For these systems, some common sensors are [[microphone]]s, [[pickup (music technology)|instrument pickups]], and [[phonograph]]s. Preamplifiers are often integrated into the audio inputs on [[mixing console]]s, [[DJ mixer]]s, and [[sound card]]s. They can also be stand-alone devices.

==Examples==

* The integrated preamplifier in a foil [[electret microphone]]
* The first stage of an [[instrument amplifier]], the output of which is then sent to the power amplifier. With instrument amplifiers, the preamp is often designed to produce [[distortion (music)|overdrive]] or distortion effects.
* A stand-alone unit for use in [[live music]] and [[recording studio]] applications
* Part of a stand-alone [[channel strip]] or channel strip built into an audio [[mixing desk]]
* A [[Radio masts and towers|masthead]] amplifier used with [[television]] receiver [[antenna (electronics)|antenna]] (For a receiver far from the antenna, it amplifies the signal and noise from the antenna, reducing the negative effects of the necessary cable length; for an antenna near a receiver, such an amplifier only adds noise.)
* A component in the electronic part of a [[satellite]] [[Receiver (radio)|receiver]] dish
* A circuit inside of a hard disk drive or tape player connected to the magnetic heads, or the circuit inside of an optical disc drive (such as CD) which connects to the [[photodiode]]s
* A [[phono stage]] amplifying the signal from a [[phonograph]] [[Magnetic cartridge|cartridge]] to the ''line-level'' input of common power amplifiers
* A [[switched capacitor]] circuit used to null the effects of mismatch offset in most [[CMOS]] comparator-based [[flash analog-to-digital converter]]s
* Due to their unique coloration, some preamplifiers can be emulated in software to be used in mixing.

==See also==
* [[Low-noise amplifier]] (LNA)
* [[Instrumentation amplifier]]
* [[Buffer amplifier]]
* [[Logarithmic resistor ladder]]

==References==
{{reflist}}

==External links==
*{{Commons category inline}}

{{music technology}}

[[Category:Electronic amplifiers]]
[[Category:Audio engineering]]