The term microphone preamplifier can either refer to the electronic circuitry within a microphone, or to a separate device or circuit that the microphone is connected to. In either instance, the purpose of the microphone preamplifier is the same. A microphone preamplifier is a sound engineering device that prepares a

microphone A microphone, colloquially called a mic or mike (), is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and pub ...

signal In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The '' IEEE Transactions on Signal Processing' ...

to be processed by other equipment. Microphone signals are often too weak to be transmitted to units such as

mixing console A mixing console or mixing desk is an electronic device for mixing audio signals, used in sound recording and reproduction and sound reinforcement systems. Inputs to the console include microphones, signals from electric or electronic inst ...

s and

recording device Recorder or The Recorder may refer to: Newspapers * '' Indianapolis Recorder'', a weekly newspaper * ''The Recorder'' (Massachusetts newspaper), a daily newspaper published in Greenfield, Massachusetts, US * ''The Recorder'' (Port Pirie), a new ...

s with adequate quality. Preamplifiers increase a microphone signal to

line level Line level is the specified strength of an audio signal used to transmit analog audio between components such as CD and DVD players, television sets, audio amplifiers, and mixing consoles. Line level sits between other levels of audio signal ...

(i.e. the level of signal strength required by such devices) by providing stable

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 d ...

while preventing induced noise that would otherwise distort the signal.Ballou, 1987, pp. 506–507. For additional discussion of signal level, see Gain stage. A microphone preamplifier is colloquially called a microphone preamp, mic preamp, micamp, preamp (not to be confused with a control amplifier in high-fidelity reproduction equipment), mic pre and pre.

Technical details

The output voltage on a

dynamic microphone A microphone, colloquially called a mic or mike (), is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and publi ...

may be very low, typically in the 1 to 100 microvolt range. A microphone preamplifier increases that level by up to 70 dB, to anywhere up to 10 volts. This stronger signal is used to drive equalization circuitry within an

audio mixer Audio most commonly refers to sound, as it is transmitted in signal form. It may also refer to: Sound *Audio signal, an electrical representation of sound *Audio frequency, a frequency in the audio spectrum * Digital audio, representation of soun ...

, to drive external audio effects, and to sum with other signals to create an audio mix for

audio recording Sound recording and reproduction is the electrical, mechanical, electronic, or digital inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording ...

or for live sound.

Functions

In addition to providing gain for the microphone signal, a microphone preamplifier as found in a sound mixer or as a discrete component typically also provides power to the microphone in the form of either 24 or 48 volt

Phantom power Phantom power, in the context of professional audio equipment, is DC electric power transmitted through microphone cables to operate microphones that contain active electronic circuitry. It is best known as a convenient power source for con ...

In use

A microphone is a

transducer A transducer is a device that converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another. Transducers are often employed at the boundaries of automation, measurement, and cont ...

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 by adding a different characteristic than the audio mixer's built-in preamplifiers. Some microphones, for example condensers, must be used in conjunction with an impedance matching preamplifier to function properly. Some preamplifiers exist as one part of a channel strip, which can include other kinds of audio recording devices such as

compressor A compressor is a mechanical device that increases the pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor. Compressors are similar to pumps: both increase the pressure on a fluid and both can trans ...

s, equalization (EQ), noise gates, and enhancers.

References

* {{Music technology Audio amplifiers Microphones