![Clipping waveform](https://upload.wikimedia.org/wikipedia/commons/c/ca/Clipping_waveform.svg)
In
electronics
The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...
, a limiter is a circuit that allows signals below a specified input power or level to pass unaffected while
attenuating
In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable a ...
(lowering) the peaks of stronger signals that exceed this threshold. Limiting is a type of
dynamic range compression
Dynamic range compression (DRC) or simply compression is an audio signal processing operation that reduces the volume of loud sounds or amplifies quiet sounds, thus reducing or ''compressing'' an audio signal's dynamic range. Compression is ...
.
Clipping
Clipping may refer to:
Words
* Clipping (morphology), the formation of a new word by shortening it, e.g. "ad" from "advertisement"
* Clipping (phonetics), shortening the articulation of a speech sound, usually a vowel
* Clipping (publications) ...
is an extreme version of limiting.
Limiting is any process by which the amplitude of a signal is prevented from exceeding a predetermined value.
Limiters are common as a safety device in live sound and broadcast applications to prevent sudden volume peaks from occurring. Limiters are also used as protective features in some components of
sound reinforcement systems (e.g., powered
mixing board
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
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 ...
s) and in some
bass amplifier
A bass amplifier (also abbreviated to bass amp) is a musical instrument electronic device that uses electrical power to make lower-pitched instruments such as the bass guitar or double bass loud enough to be heard by the performers and audien ...
s, to prevent unwanted
distortion
In signal processing, distortion is the alteration of the original shape (or other characteristic) of a signal. In communications and electronics it means the alteration of the waveform of an information-bearing signal, such as an audio signal ...
or
loudspeaker
A loudspeaker (commonly referred to as a speaker or speaker driver) is an electroacoustic transducer that converts an electrical audio signal into a corresponding sound. A ''speaker system'', also often simply referred to as a "speaker" or " ...
damage.
Types
Limiting can refer to a range of treatments designed to limit the maximum level of a signal. Treatments in order of decreasing severity range from
clipping
Clipping may refer to:
Words
* Clipping (morphology), the formation of a new word by shortening it, e.g. "ad" from "advertisement"
* Clipping (phonetics), shortening the articulation of a speech sound, usually a vowel
* Clipping (publications) ...
, in which a signal is passed through normally but sheared off when it would normally exceed a certain threshold; soft clipping which squashes peaks instead of shearing them; a hard limiter, a type of variable-gain
audio level compression
Dynamic range compression (DRC) or simply compression is an audio signal processing operation that reduces the volume of loud sounds or amplifies quiet sounds, thus reducing or ''compressing'' an audio signal's dynamic range. Compression is ...
, in which the gain of an amplifier is changed very quickly to prevent the signal from going over a certain amplitude or a soft limiter which reduces maximum output through
gain compression
Gain compression is a reduction in ''differential'' or ''slope'' gain caused by nonlinearity of the transfer function of the amplifying device. This nonlinearity may be caused by heat due to power dissipation or by overdriving the active devic ...
.
In amplifiers
Bass instrument amplifiers and power amplifiers are more commonly equipped with limiter circuitry to prevent overloading the power amplifier and to protect speakers.
Electric guitar amps do not usually have limiters.
PIN diode
A pin is a device used for fastening objects or material together.
Pin or PIN may also refer to:
Computers and technology
* Personal identification number (PIN), to access a secured system
** PIN pad, a PIN entry device
* PIN, a former Dutch ...
s can be used in limiter circuits to reflect the energy back to the source or clip the signal.
In FM radio
An
FM radio
FM broadcasting is a method of radio broadcasting using frequency modulation (FM). Invented in 1933 by American engineer Edwin Armstrong, wide-band FM is used worldwide to provide high fidelity sound over broadcast radio. FM broadcasting is cap ...
receiver usually has at least one stage of amplification that performs a limiting function. This stage provides a constant level of signal to the FM
demodulator
Demodulation is extracting the original information-bearing signal from a carrier wave. A demodulator is an electronic circuit (or computer program in a software-defined radio) that is used to recover the information content from the modulated ...
stage, reducing the effect of input signal level changes to the output. If two or more signals are received at the same time, a high-performance limiter stage can greatly reduce the effect of the weaker signals on the output. This is commonly referred to as the FM
capture effect.
Generally, FM demodulators are not affected by amplitude variations, since the baseband is contained in the
frequency deviation Frequency deviation (f_) is used in FM radio to describe the difference between the minimum or maximum extent of a frequency modulated signal, and the nominal center or carrier frequency. The term is sometimes mistakenly used as synonymous with freq ...
s. Some detectors, including the
ratio detector
The ratio detector is a type of detector circuit, commonly used in radio receivers for demodulating frequency modulated (FM) signal.
The ratio detector is a variant of the Foster–Seeley discriminator, but one diode conducts in an opposite d ...
, inherently limit gain by the nature of the circuit design. In
AM radio
AM broadcasting is radio broadcasting using amplitude modulation (AM) transmissions. It was the first method developed for making audio radio transmissions, and is still used worldwide, primarily for medium wave (also known as "AM band") transm ...
, the information is located in the amplitude variations, and distortion can occur due to spurious signals that could cause the baseband to be misrepresented.
In aerospace and military
For military two-way radio sets and aircraft VHF voice telecommunications, the voice limiter is known as a
vogad
Automatic gain control (AGC) is a closed-loop feedback regulating circuit in an amplifier or chain of amplifiers, the purpose of which is to maintain a suitable signal amplitude at its output, despite variation of the signal amplitude at the inp ...
.
It is designed to work with
high levels of background noise near the microphone. One form operates by up-converting the audio signal to a ultrasonic frequency, hard limiting that signal, and
then down converting the result. The frequency conversion uses image-cancelling heterodyning. The advantage of clipping the supersonic signal is that the odd harmonics
produced will still be out-of-band when down converted. This is in contrast to standard hard limiting, as in an electric guitar fuzz box, where the harmonics are highly audible.
This device ultimately gives a distinctive character to the voice communication, which despite being highly distorted, ensures spoken words remain clear.
In audio production
Mastering engineer
A mastering engineer is a person skilled in the practice of taking audio (typically musical content) that has been previously mixed in either the analog or digital domain as mono, stereo, or multichannel formats and preparing it for use in distr ...
s often use limiting combined with make-up gain to increase the perceived
loudness
In acoustics, loudness is the subjectivity, subjective perception of sound pressure. More formally, it is defined as, "That attribute of auditory sensation in terms of which sounds can be ordered on a scale extending from quiet to loud". The rel ...
of an audio recording during the
audio mastering
Mastering, a form of audio post production, is the process of preparing and transferring recorded audio from a source containing the final mix to a data storage device (the master), the source from which all copies will be produced (via met ...
process.
See also
*
Clipper (electronics)
In electronics, a clipper is a circuit designed to prevent a signal from exceeding a predetermined reference voltage level. A clipper does not distort the remaining part of the applied waveform. Clipping circuits are used to select, for purpose ...
*
Flow limiter
A flow limiter or flow restrictor is a device to restrict the flow of a fluid, in general a gas or a liquid. Some designs use single stage or multi stage orifice plates to handle high and low flow rates. Flow limiters are often used in manufactu ...
*
Negative feedback
Negative feedback (or balancing feedback) occurs when some function (Mathematics), function of the output of a system, process, or mechanism is feedback, fed back in a manner that tends to reduce the fluctuations in the output, whether caused by ...
*
Variable-gain amplifier
A variable-gain (VGA) or voltage-controlled amplifier (VCA) is an electronic amplifier that varies its gain depending on a control voltage (often abbreviated CV).
VCAs have many applications, including audio level compression, synthesizers and ...
References
{{FS1037C MS188
Electronic circuits
Dynamics processing