A preamplifier, also known as a preamp, is an

electronic amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a Signal (information theory), signal (a time-varying voltage or Electric current, current). It may increase the power (physics ...

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 An audio power amplifier (or power amp) is an electronic amplifier that amplifies low-power electronic audio signals, such as the signal from a radio receiver or an electric guitar pickup, to a level that is high enough for driving loudspea ...

and a loudspeaker. Without this, the final signal would be noisy or distorted. They are typically used to amplify signals from analog sensors such as microphones and pickups. Because of this, the preamplifier is often placed close to the

sensor A sensor is a device that produces an output signal for the purpose of sensing a physical phenomenon. In the broadest definition, a sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends ...

to reduce the effects of noise and interference.

Description

An ideal preamp will be linear (have a constant

gain Gain or GAIN may refer to: Science and technology * Gain (electronics), an electronics and signal processing term * Antenna gain * Gain (laser), the amplification involved in laser emission * Gain (projection screens) * Information gain in de ...

through its operating range), have high input impedance (requiring only a minimal amount of current to sense the input signal) and a 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 Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to the noise power, often expressed in deci ...

(SNR). The noise performance of a preamplifier is critical. According to 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 preamplifier * 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 amp). The preamplifier provides voltage gain (e.g., from 10 mV to 1 V) but no significant current gain. The power amplifier provides the higher current necessary to drive loudspeakers. For these systems some common sensors are microphones, instrument pickups, and

phonograph A phonograph, in its later forms also called a gramophone (as a trademark since 1887, as a generic name in the UK since 1910) or since the 1940s called a record player, or more recently a turntable, is a device for the mechanical and analogu ...

s. Preamplifiers are often integrated into the audio inputs on mixing consoles, DJ mixers, and sound cards. They can also be stand-alone devices

Examples

* The integrated preamplifier in a foil electret microphone. * The first stages of an instrument amplifier, which is then sent to the power amplifier. With instrument amplifiers, the preamp is often designed to produce

overdrive Overdrive may refer to: Organizations * OverDrive, Inc., a digital distributor of entertainment media ** OverDrive Media Console, a media player developed by OverDrive, Inc. * Overdrive PC, a subsidiary of Velocity Micro Technology * Overdrive ...

or distortion effects. * A stand-alone unit for use in

live music A concert is a live music performance in front of an audience. The performance may be by a single musician, sometimes then called a recital, or by a musical ensemble, such as an orchestra, choir, or band. Concerts are held in a wide variety an ...

and

recording studio A recording studio is a specialized facility for sound recording, mixing, and audio production of instrumental or vocal musical performances, spoken words, and other sounds. They range in size from a small in-home project studio large enoug ...

applications. * As part of a stand-alone channel strip or channel strip built into an audio mixing desk. * A

masthead Masthead may refer to: * Nameplate (publishing), the banner name on the front page of a newspaper or periodical (UK "masthead") * Masthead (American publishing), details of the owners, publisher, departments, officers, contributors and address d ...

amplifier used with television receiver

antenna Antenna ( antennas or antennae) may refer to: Science and engineering * Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves * Antennae Galaxies, the name of two collid ...

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

photodiode A photodiode is a light-sensitive semiconductor diode. It produces current when it absorbs photons. The package of a photodiode allows light (or infrared or ultraviolet radiation, or X-rays) to reach the sensitive part of the device. The packag ...

s. * A

switched capacitor A switched capacitor (SC) is an electronic circuit that implements a function by moving charges into and out of capacitors when electronic switches are opened and closed. Usually, non-overlapping clock signals are used to control the switches, so ...

circuit used to null the effects of mismatch offset in most

CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss", ) is a type of metal–oxide–semiconductor field-effect transistor (MOSFET) fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSFE ...

comparator-based flash analog-to-digital converters * Due to its unique coloration, some preamplifiers can be emulated in software to be used in mixing.

External links

* {{music technology Electronic amplifiers Audio engineering

Description

Audio systems

Examples

See also

External links