Microphone preamp
Encyclopedia
A microphone preamplifier is a sound engineering device that prepares a microphone
signal to be processed by other equipment. Microphone signals are normally too weak to be transmitted to units such as mixing console
s and recording devices. Preamplifiers increase a microphone signal to line-level (i.e. the level of signal strength required by such devices) by providing stable gain
while preventing induced noise that would otherwise distort the signal.
The microphone preamplifiers are colloquially called microphone preamp, mic preamp, preamp (not to be confused with a control amplifier in high-fidelity
reproduction equipment), mic pre and pre.
, to approximately 0 to 10 volts. This stronger signal is used to drive equalization circuitry within an audio mixer, to drive external audio effects, and to sum with other signals to create an audio mix for audio recording and for live sound.
and, as such, is the source of much of the coloration of an audio mix. Most audio engineers would assert that a microphone preamplifier also affects the sound quality of an audio mix. A preamplifier might load the microphone with low impedance, forcing the microphone to work harder and so change its tone quality. A preamplifier might add coloration for adding a different characteristic than the audio mixer's built-in preamplifiers. Some microphones must be used in conjunction with a preamplifier to function properly (e.g.Condenser microphones)
Some preamplifiers exist as one part of a channel strip
, which can include other kinds of audio recording devices such as compressors, equalization
(EQ), noise gate
s, and enhancers
.
Microphone
A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1877, Emile Berliner invented the first microphone used as a telephone voice transmitter...
signal to be processed by other equipment. Microphone signals are normally too weak to be transmitted to units such as mixing console
Mixing console
In professional audio, a mixing console, or audio mixer, also called a sound board, mixing desk, or mixer is an electronic device for combining , routing, and changing the level, timbre and/or dynamics of audio signals. A mixer can mix analog or digital signals, depending on the type of mixer...
s and recording devices. Preamplifiers increase a microphone signal to line-level (i.e. the level of signal strength required by such devices) by providing stable gain
Gain
In electronics, gain is a measure of the ability of a circuit to increase the power or amplitude of a signal from the input to the output. It is usually defined as the mean ratio of the signal output of a system to the signal input of the same system. It may also be defined on a logarithmic scale,...
while preventing induced noise that would otherwise distort the signal.
The microphone preamplifiers are colloquially called microphone preamp, mic preamp, preamp (not to be confused with a control amplifier in high-fidelity
High fidelity
High fidelity—or hi-fi—reproduction is a term used by home stereo listeners and home audio enthusiasts to refer to high-quality reproduction of sound or images, to distinguish it from the poorer quality sound produced by inexpensive audio equipment...
reproduction equipment), mic pre and pre.
Technical details
The output voltage on a dynamic microphone may be very low, typically in the 0 to 100 microvolt range. A microphone preamplifier increases that level by up to 70 dBDecibel
The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
, to approximately 0 to 10 volts. This stronger signal is used to drive equalization circuitry within an audio mixer, to drive external audio effects, and to sum with other signals to create an audio mix for audio recording and for live sound.
In use
A microphone is a transducerTransducer
A transducer is a device that converts one type of energy to another. Energy types include electrical, mechanical, electromagnetic , chemical, acoustic or thermal energy. While the term transducer commonly implies the use of a sensor/detector, any device which converts energy can be considered a...
and, as such, is the source of much of the coloration of an audio mix. Most audio engineers would assert that a microphone preamplifier also affects the sound quality of an audio mix. A preamplifier might load the microphone with low impedance, forcing the microphone to work harder and so change its tone quality. A preamplifier might add coloration for adding a different characteristic than the audio mixer's built-in preamplifiers. Some microphones must be used in conjunction with a preamplifier to function properly (e.g.Condenser microphones)
Some preamplifiers exist as one part of a channel strip
Channel strip
A channel strip is a device that allows the output of an audio device to be amplified to a line level and integrated into some other system. An audio channel strip may be a stand alone unit or one of many units built into a mixing desk. It usually includes a microphone preamp with a switchable...
, which can include other kinds of audio recording devices such as compressors, equalization
Equalization (audio)
Equalization is the process commonly used in sound recording and reproduction to alter the frequency response of an audio system using linear filters. Most hi-fi equipment uses relatively simple filters to make bass and treble adjustments. Graphic and parametric equalizers have much more...
(EQ), noise gate
Noise gate
A Noise Gate or gate is an electronic device or software that is used to control the volume of an audio signal. In its most simple form, a noise gate allows a signal to pass through only when it is above a set threshold: the gate is 'open'. If the signal falls below the threshold no signal is...
s, and enhancers
Exciter (effect)
An Exciter is an audio signal processing technique used to enhance a signal by dynamic equalization, phase manipulation, harmonic synthesis of high frequency signals, and through the addition of subtle harmonic distortion...
.