In an
amplifier
An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost the v ...
, a presence control boosts the upper mid-range frequencies to make the sounds of voices and instruments with similar tonal ranges seem more "present".
On television production studio's sound desk, there can be several presence controls, for several different, switchable, frequencies. There is a limit to the flexibility of such controls, and they are sometimes insufficient. If the degree of mis-match between microphones is great, simply increasing presence is not enough, and instead a sound engineer will use a
graphic equalizer, sometimes several, each connected to an individual sound channel.
Presence controls can also be found on
electric guitar
An electric guitar is a guitar that requires external amplification in order to be heard at typical performance volumes, unlike a standard acoustic guitar (however combinations of the two - a semi-acoustic guitar and an electric acoustic gui ...
amplifiers. The first presence control on a
Fender amplifier, for example, appeared in 1954 on the
Twin
Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of TwinLast Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two em ...
. In 1955 it appeared on the 1/15 Pro-Amp, the 3/10
Bandmaster
A bandmaster is the leader and conductor of a band, usually a concert band, military band, brass band or a marching band.
British Armed Forces
In the British Army, bandmasters of the Royal Corps of Army Music now hold the rank of staff s ...
, the 2/10
Super
Super may refer to:
Computing
* SUPER (computer program), or Simplified Universal Player Encoder & Renderer, a video converter / player
* Super (computer science), a keyword in object-oriented programming languages
* Super key (keyboard butt ...
, and the 4/10
Bassman. The original Fender presence control acted upon the amplifier's negative-feedback loop. As the level of "presence" was increased, so more and more of the higher frequencies in the negative-feedback loop were dumped to ground, leaving the low and mid-range frequencies. Increasing the presence resulted in there being less and less negative feedback on high frequencies. The effect varied according to
amplitude
The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of amplit ...
.
Later Fender amplifiers used a different presence control. The presence control on the 1975 Fender Super Twin did not modify the negative feedback loop, but was an
active equalization circuit, controlling the 3.9 kHz frequency range. It had the ability to both amplify (boost) and attenuate (cut), unlike the earlier presence control.
In a 3-way loudspeaker system, with
tweeter,
woofer, and
mid-range speaker, a presence control is simply a volume control for the mid-range speaker.
[{{cite encyclopedia, article=presence control, encyclopedia=Modern Dictionary of Electronics, author=Rudolf F. Graf, pages=586, publisher=Newnes, year=1999, isbn=0-7506-9866-7]
References
Tone, EQ and filter