The Azimuth Co-ordinator was the first panning control for a quadraphonic sound system , at that time a new concept. Pink Floyd became the first band to use it in their early shows.
106-412: The Azimuth Co-ordinator uses four rotary rheostats housed in a large box. The rheostats were converted from their standard 270 degrees rotation to operate over the narrower 90 degree range imposed by the physical constraints of the control lever with the box top aperture. The system was operated using two joysticks, which allowed an audio signal to be panned between up to six loudspeakers placed around
212-419: A function generator , using a non-linear resistance card to supply approximations to trigonometric functions. For example, the shaft rotation might represent an angle, and the voltage division ratio can be made proportional to the cosine of the angle. The potentiometer can be used as a voltage divider to obtain a manually adjustable output voltage at the slider (wiper) from a fixed input voltage applied across
318-427: A graph of the equalizer's response plotted versus frequency. The number of frequency channels may be matched to the requirements of the intended application. A car audio equalizer might have a total of five to ten frequency bands. An equalizer for professional live sound reinforcement typically has some 25 to 31 bands, for more precise control of feedback problems and equalization of room modes . Such an equalizer
424-499: A joystick . Potentiometers are rarely used to directly control significant power (more than a watt ), since the power dissipated in the potentiometer would be comparable to the power in the controlled load. Some terms in the electronics industry used to describe certain types of potentiometers are: Potentiometers consist of a resistive element , a sliding contact (wiper) that moves along the element, making good electrical contact with one part of it, electrical terminals at each end of
530-422: A potentiometer is essentially a voltage divider used for measuring electric potential (voltage); the component is an implementation of the same principle, hence its name. Potentiometers are commonly used to control electrical devices such as volume controls on audio equipment. It is also used in speed control of fans. Potentiometers operated by a mechanism can be used as position transducers , for example, in
636-422: A capacitor and resistor. Second-order filters are capable of resonance (or anti-resonance) around a particular frequency. The response of a second-order filter is specified not only by its frequency but also its Q ; a higher Q corresponds to a sharper response (smaller bandwidth) around a particular center frequency. For instance, the red response in the accompanying image cuts frequencies around 100 Hz with
742-409: A ceramic/metal mixture called cermet . Conductive track potentiometers use conductive polymer resistor pastes that contain hard-wearing resins and polymers, solvents, and lubricant, in addition to the carbon that provides the conductive properties. Multiturn potentiometers are also operated by rotating a shaft, but by several turns rather than less than a full turn. Some multiturn potentiometers have
848-486: A circuit. The word rheostat was coined in 1843 by Sir Charles Wheatstone , from the Greek ῥέος rheos meaning "stream", and - στάτης - states (from ἱστάναι histanai , "to set, to cause to stand") meaning "setter, regulating device", which is a two-terminal variable resistor. For low-power applications (less than about 1 watt) a three-terminal potentiometer is often used, with one terminal unconnected or connected to
954-404: A combination of first-order responses and second-order responses (implemented as so-called biquad sections). These can be described according to their so-called pole and zero frequencies, which are complex numbers in the case of second-order responses. A first-order filter can alter the response of frequencies above and below a point. In the transition region the filter response will have
1060-701: A cut above the rest. Today, many non-British companies such as Behringer and Mackie advertise British EQ on their equipment. A British style EQ seeks to replicate the qualities of the expensive British mixing consoles. Filtering audio frequencies dates back at least to acoustic telegraphy and multiplexing in general. Audio electronic equipment evolved to incorporate filtering elements as consoles in radio stations began to be used for recording as much as broadcast. Early filters included basic bass and treble controls featuring fixed frequency centers, and fixed levels of cut or boost. These filters worked over broad frequency ranges. Variable equalization in audio reproduction
1166-441: A first-order response and provide an adjustable boost or cut to frequencies above or below a certain point. A high shelf or treble control will have a frequency response | H ( f )| whose square is given by: where f p and f z are called the pole and zero frequencies, respectively. Turning down the treble control increases f z and decreases f p so that frequencies higher than f p are attenuated. Turning up
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#17328518912811272-429: A fixed center frequency and Q factor , but an adjustable level. The user can raise or lower each slider in order to visually approximate a graph of the intended frequency response. Equalization in the context of audio reproduction is not used strictly to compensate for the deficiency of equipment and transmission channels. A high-pass filter modifies a signal by eliminating only lower frequencies. An example of this
1378-431: A higher Q than the blue response which boosts frequencies around 1000 Hz. Higher Q's correspond to resonant behaviour in which the half-power or −3 dB bandwidth, BW , is given by: where F 0 is the resonant frequency of the second-order filter. BW is the bandwidth expressed in the same frequency unit that F 0 is. Low Q filter responses (where Q < 1 ⁄ 2 ) are not said to be resonant and
1484-450: A linear resistive element with a sliding contact moved by a lead screw; others have a helical resistive element and a wiper that turns through 10, 20, or more complete revolutions, moving along the helix as it rotates. Multiturn potentiometers, both user-accessible and preset, allow finer adjustments; rotation through the same angle changes the setting by typically a tenth as much as for a simple rotary potentiometer. A string potentiometer
1590-436: A logarithmic law. The two resistive tracks overlap at approximately 50% of the potentiometer rotation; this gives a stepwise logarithmic taper. A logarithmic potentiometer can also be simulated with a linear one and an external resistor. True logarithmic potentiometers are significantly more expensive. Logarithmic taper potentiometers are often used for volume or signal level in audio systems, as human perception of audio volume
1696-524: A low-pass filter is used in the signal chain before a subwoofer to ensure that only deep bass frequencies reach the subwoofer. While high-pass and low-pass filters are useful for removing unwanted signal above or below a set frequency, shelving filters can be used to reduce or increase signals above or below a set frequency. Shelving filters are used as common tone controls (bass and treble) found in consumer audio equipment such as home stereos, and on guitar amplifiers and bass amplifiers . These implement
1802-416: A microphone, it is further reamplified; this recirculation of sound can lead to "howling", requiring the sound technician to reduce the gain for that microphone, perhaps sacrificing the contribution of a singer's voice, for instance. Even at a slightly reduced gain, the feedback will still cause an unpleasant resonant sound around the frequency at which it would howl. But because the feedback is troublesome at
1908-498: A mix, creating the impression that some sounds in a mono or stereo mix are farther away or closer than others. Equalization is also commonly used to give tracks with similar frequency components complementary spectral contours, known as mirrored equalization . Selected components of parts that would otherwise compete, such as bass guitar and kick drum, are boosted in one part and cut in the other, and vice versa, so that they both stand out. Equalizers can correct problems posed by
2014-479: A more limited range, since their purpose is not to eliminate any frequencies but only to achieve a greater balance when, for instance, the treble is lacking and the sound is not crisp. Since the range of possible responses from shelving filters is so limited, some audio engineers considered shelving controls inadequate for equalization tasks. On some bass amps and DI boxes , the units provide both low and high shelving controls and additional equalization controls. In
2120-422: A narrow range of frequencies. In addition to specifying the center frequency F 0 and the Q, the specification of the filter's zeros determines how much that frequency band will be boosted (or cut). Thus a parametric equalizer section will have three controls for its center frequency F 0 , bandwidth or Q, and the amount of boost or cut usually expressed in dB . The range of second-order filter functions
2226-482: A non-contact potentiometer can be found with the AS5600 integrated circuit. However, absolute encoders must also use similar principles, although being for industrial use, certainly the cost must be unfeasible for use in domestic appliances. The most common way to vary the resistance in a circuit continuously is to use a rheostat . Because of the change in resistance, they can also be used to adjust magnitude of current in
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#17328518912812332-408: A particular frequency, it is possible to cut the gain only around that frequency while preserving the gain at most other frequencies. This can best be done using a parametric equalizer tuned to that very frequency with its amplitude control sharply reduced. By adjusting the equalizer for a narrow bandwidth (high Q), most other frequency components will not be affected. The extreme case when the signal at
2438-427: A percentage is referenced with a non-linear taper, it relates to the resistance value at the midpoint of the shaft rotation. A 10% log taper would therefore measure 10% of the total resistance at the midpoint of the rotation; i.e. 10% log taper on a 10 kOhm potentiometer would yield 1 kOhm at the midpoint. The higher the percentage, the steeper the log curve. A linear taper potentiometer ( linear describes
2544-416: A potentiometer has a resistance, taper, or, "curve" (or law) of a logarithmic (log) form, is used as the volume control in audio power amplifiers , where it is also called an "audio taper pot", because the amplitude response of the human ear is approximately logarithmic. It ensures that on a volume control marked 0 to 10, for example, a setting of 5 sounds subjectively half as loud as a setting of 10. There
2650-406: A room's acoustics , as an auditorium will generally have an uneven frequency response especially due to standing waves and acoustic dampening . For instance, the frequency response of a room may be analyzed using a spectrum analyzer and a pink noise generator. Then a graphic equalizer can be easily adjusted to compensate for the room's acoustics. Such compensation can also be applied to tweak
2756-544: A sharper or more "brilliant" sound, or can be used to cut such high frequencies when they have been overemphasized in the program material or simply to accommodate a listener's preference. A "rumble filter" is a high-pass (low cut) filter with a cutoff typically in the 20 to 40 Hz range; this is the low frequency end of human hearing . "Rumble" is a type of low-frequency noise produced in record players and turntables, particularly older or low quality models. The rumble filter prevents this noise from being amplified and sent to
2862-463: A slope of up to 6 dB per octave . The bass and treble controls in a hi-fi system are each a first-order filter in which the balance of frequencies above and below a point are varied using a single knob. A special case of first-order filters is a first-order high-pass or low-pass filter in which the 6 dB per octave cut of low or high frequencies extends indefinitely. These are the simplest of all filters to implement individually, requiring only
2968-463: A small area works well. A disadvantage is that sufficient force must be applied to make contact. Another is that the sensor requires occasional calibration to match touch location to the underlying display. (Capacitive sensors require no calibration or contact force, only proximity of a finger or other conductive object. However, they are significantly more complex.) Potentiometers are rarely used to directly control significant amounts of power (more than
3074-411: A switch labeled high cut or described as a hiss filter (hiss being high-frequency noise ). In the phonograph era, many stereos would include a switch to introduce a high-pass (low cut) filter, often called a rumble filter , to eliminate infrasonic frequencies. High and low-pass filters are used in audio crossovers to direct energy to the speaker drivers capable of reproducing it. For instance,
3180-427: A tunable EQ for a new recording console. Bob Meushaw, a friend of Massenburg, built the equalizer. According to Massenburg, "Four people could possibly lay claim to the modern concept: Bob Meushaw, Burgess Macneal, Daniel Flickinger, and myself… Our (Bob’s, Burgess’ and my) sweep-tunable EQ was borne, more or less, out of an idea that Burgess and I had around 1966 or 1967 for an EQ… three controls adjusting, independently,
3286-522: A very wide variety of equipment functions. The widespread use of potentiometers in consumer electronics declined in the 1990s, with rotary incremental encoders , up/down push-buttons , and other digital controls now more common. However they remain in many applications, such as volume controls and as position sensors. Low-power potentiometers, both slide and rotary, are used to control audio equipment, changing loudness, frequency attenuation, and other characteristics of audio signals. The 'log pot', that is,
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3392-419: A visual indication of its setting. While the setting of a rotary potentiometer can be seen by the position of a marking on the knob, an array of sliders can give a visual impression of settings as in a graphic equalizer or faders on a mixing console . The resistive element of inexpensive potentiometers is often made of graphite . Other materials used include resistance wire, carbon particles in plastic, and
3498-529: A watt or so). Instead they are used to adjust the level of analog signals (for example volume controls audio equipment ), and as control inputs for electronic circuits. For example, a light dimmer uses a potentiometer to control the switching of a TRIAC and so indirectly to control the brightness of lamps. Preset potentiometers are widely used throughout electronics wherever adjustments must be made during manufacturing or servicing. User-actuated potentiometers are widely used as user controls, and may control
3604-453: Is a filter, an electronic circuit or device, that passes higher frequencies well but attenuates lower-frequency components. A low-pass filter passes low-frequency components of signals while attenuating higher frequencies. In audio applications these high-pass and low-pass filters are frequently termed low cut and high cut , respectively, to emphasize their effect on the original signal. For instance, sometimes audio equipment will include
3710-403: Is a low-cut or rumble filter , which is used to remove infrasonic energy from a program that may consume undue amplifier power and cause excessive diaphragm excursions in (or even damage to) loudspeakers. A low-pass filter only modifies the audio signal by removing high frequencies. An example of this is a high-cut or hiss filter , which is used to remove annoying white noise at the expense of
3816-484: Is a multi-turn potentiometer operated by an attached reel of wire turning against a spring, allowing it to convert linear position to a variable resistance. User-accessible rotary potentiometers can be fitted with a switch which operates usually at the anti-clockwise extreme of rotation. Before digital electronics became the norm such a component was used to allow radio and television receivers and other equipment to be switched on at minimum volume with an audible click, then
3922-457: Is also an anti-log pot or reverse audio taper which is simply the reverse of a logarithmic potentiometer. It is almost always used in a ganged configuration with a logarithmic potentiometer, for instance, in an audio balance control. Potentiometers used in combination with filter networks act as tone controls or equalizers . In audio systems, the word linear, is sometimes applied in a confusing way to describe slide potentiometers because of
4028-425: Is called a 1/3-octave equalizer (spoken informally as " third-octave EQ") because the center frequencies of its filters are spaced one third of an octave apart, three filters to an octave. Equalizers with half as many filters per octave are common where less precise control is required—this design is called a 2/3-octave equalizer. Parametric equalizers are multi-band variable equalizers that allow users to control
4134-548: Is designed to follow a logarithmic taper, aka a mathematical exponent or "squared" profile. A logarithmic taper potentiometer is constructed with a resistive element that either "tapers" in from one end to the other, or is made from a material whose resistivity varies from one end to the other. This results in a device where output voltage is a logarithmic function of the slider position. Most (cheaper) "log" potentiometers are not accurately logarithmic, but use two regions of different resistance (but constant resistivity) to approximate
4240-512: Is important because any analog filter function can be decomposed into a (usually small) number of these (plus, perhaps, simpler first-order responses). These are implemented directly by each section of a parametric equalizer where they are explicitly adjusted. And each element of a graphic equalizer based on a filter bank includes one such element whose Q is not adjustable by the user. In sound recording , equalization may be used to adjust frequency responses for practical or aesthetic reasons, where
4346-432: Is introduced by the radio is then also de-emphasized at the higher frequencies (where it is most noticeable) along with the pre-emphasized program, making the noise less audible. Tape recorders used the same approach to reduce " tape hiss " while maintaining fidelity. On the other hand, in the production of vinyl records , a filter is used to reduce the amplitude of low frequencies which otherwise produce large amplitudes on
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4452-1042: Is large compared to the other resistances (like the input to an operational amplifier ), the output voltage can be approximated by the simpler equation: V L = R 2 R 1 + R 2 ⋅ V s . {\displaystyle V_{\mathrm {L} }={R_{2} \over R_{1}+R_{2}}\cdot V_{s}.} (dividing throughout by R L and cancelling terms with R L as denominator) As an example, assume V S = 10 V {\displaystyle V_{\mathrm {S} }=10\ \mathrm {V} } , R 1 = 1 k Ω {\displaystyle R_{1}=1\ \mathrm {k\Omega } } , R 2 = 2 k Ω {\displaystyle R_{2}=2\ \mathrm {k\Omega } } , and R L = 100 k Ω . {\displaystyle R_{\mathrm {L} }=100\ \mathrm {k\Omega } .} Since
4558-532: Is logarithmic, according to the Weber–Fechner law . Unlike mechanical potentiometers, non-contact potentiometers use an optical disk to trigger an infrared sensor, or a magnet to trigger a magnetic sensor (as long as there are other types of sensors, such as capacitive, other types of non-contact potentiometers can probably be built), and then an electronic circuit does the signal processing to provide an output signal that can be analogue or digital. An example of
4664-579: Is now broadly used to describe the application of such filters regardless of intent. This broad definition, therefore, includes all linear filters at the disposal of a listener or engineer. A British EQ or British style equalizer is one with similar properties to those on mixing consoles made in the UK by companies such as Amek, Neve and Soundcraft from the 1950s through to the 1970s. Later on, as other manufacturers started to market their products, these British companies began touting their equalizers as being
4770-510: Is proportional to the fraction of the total device resistance in circuit. Carbon-pile rheostats are used as load banks for testing automobile batteries and power supplies. A digital potentiometer (often called digipot) is an electronic component that mimics the functions of analog potentiometers. Through digital input signals, the resistance between two terminals can be adjusted, just as in an analog potentiometer. There are two main functional types: volatile, which lose their set position if power
4876-433: Is removed, and are usually designed to initialise at the minimum position, and non-volatile, which retain their set position using a storage mechanism similar to flash memory or EEPROM . Usage of a digipot is far more complex than that of a simple mechanical potentiometer, and there are many limitations to observe; nevertheless they are widely used, often for factory adjustment and calibration of equipment, especially where
4982-870: Is the process of adjusting the volume of different frequency bands within an audio signal . The circuit or equipment used to achieve this is called an equalizer . Most hi-fi equipment uses relatively simple filters to make bass and treble adjustments. Graphic and parametric equalizers have much more flexibility in tailoring the frequency content of an audio signal. Broadcast and recording studios use sophisticated equalizers capable of much more detailed adjustments, such as eliminating unwanted sounds or making certain instruments or voices more prominent. Because of this ability, they can be aptly described as "frequency-specific volume knobs." Equalizers are used in recording and radio studios , production control rooms , and live sound reinforcement and in instrument amplifiers , such as guitar amplifiers , to correct or adjust
5088-456: Is the simplest method of measuring the angle or displacement. Potentiometers are also very widely used as a part of displacement transducers because of the simplicity of construction and because they can give a large output signal. In analog computers , high precision potentiometers are used to scale intermediate results by desired constant factors, or to set initial conditions for a calculation. A motor-driven potentiometer may be used as
5194-550: Is used, but the letter code definitions are not standardized. Potentiometers made in Asia and the US are usually marked with an "A" for logarithmic taper or a "B" for linear taper; "C" for the rarely seen reverse logarithmic taper. Others, particularly those from Europe, may be marked with an "A" for linear taper, a "C" or "B" for logarithmic taper, or an "F" for reverse logarithmic taper. The code used also varies between different manufacturers. When
5300-408: The cutoff frequencies . A low shelf , such as the bass control on most hi-fi equipment, is adjusted to affect the gain of lower frequencies while having no effect well above its cutoff frequency. A high shelf , such as a treble control, adjusts the gain of higher frequencies only. These are broad adjustments designed more to increase the listener's satisfaction than to provide actual equalization in
5406-446: The cutoff frequency . For instance, a second-order low-pass notch filter section only reduces (rather than eliminates) very high frequencies, but has a steep response falling to zero at a specific frequency (the so-called notch frequency ). Such a filter might be ideal, for instance, in completely removing the 19 kHz FM stereo subcarrier pilot signal while helping to cut even higher frequency subcarrier components remaining from
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#17328518912815512-416: The graphic equalizer , the input signal is sent to a bank of filters . Each filter passes the portion of the signal present in its own frequency range or band . The amplitude passed by each filter is adjusted using a slide control to boost or cut frequency components passed by that filter. The vertical position of each slider thus indicates the gain applied to that frequency band, so that the sliders resemble
5618-419: The timbre of individual instruments and voices by adjusting their frequency content and to fit individual instruments within the overall frequency spectrum of the mix . The concept of equalization was first applied in correcting the frequency response of telephone lines using passive filters ; this was prior to the invention of electronic amplification. Initially, equalization was used to compensate for
5724-404: The "potentiometer" every time the equipment is powered up, a multiplying DAC can be used in place of a digipot, and this can offer higher setting resolution, less drift with temperature, and more operational flexibility. A membrane potentiometer uses a conductive membrane that is deformed by a sliding element to contact a resistor voltage divider. Linearity can range from 0.50% to 5% depending on
5830-473: The V&;A's 2017 Their Mortal Remains exhibition. [REDACTED] Media related to Azimuth Co-ordinators at Wikimedia Commons Rheostat A potentiometer is a three- terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider . If only two terminals are used, one end and the wiper, it acts as a variable resistor or rheostat . The measuring instrument called
5936-406: The above formula for bandwidth does not apply. It is also possible to define the Q of a band-pass function as: where N is the bandwidth in octaves. The reverse mapping is: A second-order filter response with Q of less than 1/2 can be decomposed into two first-order filter functions, a low-cut and a high-cut (or boost). Of more interest are resonant filter functions which can boost (or cut)
6042-470: The center frequency selected. In a semi-parametric equalizer the bandwidth is preset by the designer. In a quasi-parametric equalizer, the user is given limited switchable options for bandwidth. A graphic equalizer also implements second-order filter functions in a more user-friendly manner but with somewhat less flexibility. This equipment is based on a bank of filters covering the audio spectrum in up to 31 frequency bands . Each second-order filter has
6148-412: The centering of the display on an analog cathode-ray oscilloscope . Precision potentiometers have an accurate relationship between resistance and slider position. A logarithmic taper potentiometer is a potentiometer that has a bias built into the resistive element. Basically this means the center position of the potentiometer is not one half of the total value of the potentiometer. The resistive element
6254-423: The channel or recording process. At the end of the channel or when the recording is played, a complementary filter is inserted which precisely compensates for the original filter and recovers the original waveform. For instance, FM broadcasting uses a pre-emphasis filter to boost the high frequencies before transmission, and every receiver includes a matching de-emphasis filter to restore it. The white noise that
6360-518: The circuit topology that would come to dominate audio equalization until the present day, as well as the theoretical underpinnings of the elegant circuit. Instead of slide potentiometers working on individual bands of frequency, or rotary switches, Flickinger's circuit allowed arbitrary selection of frequency and cut or boost level in three overlapping bands over the entire audio spectrum. Six knobs on his early EQs would control these sweepable filters. Up to six switches were incorporated to select shelving on
6466-435: The crispness of the program material. A first-order low-pass or high-pass filter has a standard response curve that reduces the unwanted frequencies well above or below the cutoff frequency with a slope of 6 dB per octave. A second-order filter will reduce those frequencies with a slope of 12 dB per octave and moreover may be designed with a higher Q or finite zeros in order to effect an even steeper response around
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#17328518912816572-476: The electrical characteristic of the device, not the geometry of the resistive element) has a resistive element of constant cross-section, resulting in a device where the resistance between the contact (wiper) and one end terminal is proportional to the distance between them. Linear taper potentiometers are used when the division ratio of the potentiometer must be proportional to the angle of shaft rotation (or slider position), for example, controls used for adjusting
6678-426: The element, a mechanism that moves the wiper from one end to the other, and a housing containing the element and wiper. Many inexpensive potentiometers are constructed with a resistive element (B in cutaway drawing) formed into an arc of a circle usually a little less than a full turn and a wiper (C) sliding on this element when rotated, making electrical contact. The resistive element can be flat or angled. Each end of
6784-407: The end result typically is unequal volume levels for the different frequencies. For example, equalization is used to modify an instrument's sound or make certain instruments and sounds more prominent. A recording engineer may use an equalizer to make some high-pitches in a vocal part louder while making low-pitches in a drum part quieter. Equalization is commonly used to increase the depth of
6890-466: The filter's center frequency is completely eliminated is known as a notch filter . An equalizer can be used to correct or modify the frequency response of a loudspeaker system rather than designing the speaker itself to have the desired response. For instance, the Bose 901 speaker system does not use separate larger and smaller drivers to cover the bass and treble frequencies. Instead it uses nine drivers all of
6996-420: The form of variable bass and treble controls, and switches to apply low-cut or high-cut filters for elimination of low-frequency rumble and high-frequency hiss respectively. Graphic equalizers and other equipment developed for improving fidelity have since been used by recording engineers to modify frequency responses for aesthetic reasons. Hence in the field of audio electronics the term equalization
7102-406: The frequency response in recording, reproduction, and live sound reinforcement systems . Sound engineers correct the frequency response of a sound system so that the frequency balance of the music as heard through speakers better matches the original performance picked up by a microphone . Audio amplifiers have long had filters or controls to modify their frequency response. These are most often in
7208-456: The genericized brand name "trimpot". The relationship between slider position and resistance, known as the "taper" or "law", can be controlled during manufacture by changing the composition or thickness of the resistance coating along the resistance element. Although in principle any taper is possible, two types are widely manufactured: linear and logarithmic (aka "audio taper") potentiometers. A letter code may be used to identify which taper
7314-473: The hall. During Pink Floyd's live shows, the Azimuth Co-ordinator was operated by keyboardist Rick Wright . As he operated the joystick, the source of the sound moved from speaker to speaker around the auditorium. With the controls in the central position, the sound output would be equal in all speakers. It was constructed by technical engineer Bernard Speight at EMI Recording Studios . The original
7420-473: The high and low bands, and bypassing for any unused band for the purest signal path. Similar designs appeared soon thereafter from George Massenburg (in 1972) and Burgess McNeal from ITI corp. In May 1972 Massenburg used the term parametric equalization in a paper presented at the 42nd convention of the Audio Engineering Society . Most channel equalization on mixing consoles made from 1971 to
7526-410: The inclusion of the leading factor simply indicates that the response at frequencies much higher than f z or f p is unity and that only bass frequencies are affected. A high shelving control in which f z is set to infinity, or a low shelving response in which f z is set to zero, implements a first-order low-pass or high-pass filter, respectively. However, the usual tone controls have
7632-431: The knob. Other potentiometers are enclosed within the equipment and are intended to only be adjusted when calibrating the equipment during manufacture or repair, and not otherwise touched. They are usually physically much smaller than user-accessible potentiometers, and may need to be operated by a screwdriver rather than having a knob. They are usually called "trimmer", "trim[ming]", or "preset" potentiometers (or pots), or
7738-488: The limitations of mechanical potentiometers are problematic. A digipot is generally immune to the effects of moderate long-term mechanical vibration or environmental contamination, to the same extent as other semiconductor devices, and can be secured electronically against unauthorised tampering by protecting the access to its programming inputs by various means. In equipment which has a microprocessor , FPGA or other functional logic which can store settings and reload them to
7844-605: The load resistance is large compared to the other resistances, the output voltage V L will be approximately: 2 k Ω 1 k Ω + 2 k Ω ⋅ 10 V = 2 3 ⋅ 10 V ≈ 6.667 V . {\displaystyle {2\ \mathrm {k\Omega } \over 1\ \mathrm {k\Omega } +2\ \mathrm {k\Omega } }\cdot 10\ \mathrm {V} ={2 \over 3}\cdot 10\ \mathrm {V} \approx 6.667\ \mathrm {V} .} Because of
7950-417: The load resistance, however, it will actually be slightly lower: ≈ 6.623 V . One of the advantages of the potential divider compared to a variable resistor in series with the source is that, while variable resistors have a maximum resistance where some current will always flow, dividers are able to vary the output voltage from maximum ( V S ) to ground (zero volts) as the wiper moves from one end of
8056-400: The loudspeakers. Some cassette decks have a switchable "subsonic filter" feature that does the same thing for recordings. A crossover network is a system of filters designed to direct electrical energy separately to the woofer and tweeter of a 2-way speaker system (and also to the mid-range speaker of a 3-way system). This is most often built into the speaker enclosure and hidden from
8162-412: The manufacturer. Tone controls (usually designated "bass" and "treble") are simple shelving filters included in most hi-fi equipment for gross adjustment of the frequency balance. The bass control may be used, for instance, to increase the drum and bass parts at a dance party, or to reduce annoying bass sounds when listening to a person speaking. The treble control might be used to give the percussion
8268-662: The material, design and manufacturing process. The repeat accuracy is typically between 0.1 mm and 1.0 mm with a theoretically infinite resolution. The service life of these types of potentiometers is typically 1 million to 20 million cycles depending on the materials used during manufacturing and the actuation method; contact and contactless (magnetic) methods are available (to sense position). Many different material variations are available such as PET , FR4, and Kapton. Membrane potentiometer manufacturers offer linear, rotary, and application-specific variations. The linear versions can range from 9 mm to 1000 mm in length and
8374-406: The other two, formerly unconnected, provides the other coordinate. Alternating rapidly between pairs of edges provides frequent position updates. An analog-to-digital converter provides output data. Advantages of such sensors are that only five connections to the sensor are needed, and the associated electronics is comparatively simple. Another is that any material that depresses the top layer over
8480-593: The parameters for each of three bands for a recording console… I wrote and delivered the AES paper on Parametrics at the Los Angeles show in 1972… It’s the first mention of 'Parametric' associated with sweep-tunable EQ." Daniel N. Flickinger introduced the first parametric equalizer in early 1971. His design leveraged a high-performance op-amp of his own design, the 535 series to achieve filtering circuits that were before impossible. Flickinger's patent from early in 1971 showed
8586-513: The parametric equalizer is the semi-parametric equalizer, which is also known as a sweepable filter. It allows users to control the amplitude and frequency, but uses a pre-set bandwidth of the center frequency. In some cases, semi-parametric equalizers allow the user to select between a wide and a narrow preset bandwidth. The responses of linear filters are mathematically described in terms of their transfer function or, in layman's terms, frequency response . A transfer function can be decomposed as
8692-549: The potentiometer to the other. There is, however, always a small amount of contact resistance . In addition, the load resistance is often not known and therefore simply placing a variable resistor in series with the load could have a negligible effect or an excessive effect, depending on the load. Ageing may cause intermittent contact between the resistive track and the wiper as it is rotated. In volume control use this causes crackling. Graphic equalizer Equalization , or simply EQ , in sound recording and reproduction
8798-428: The present day rely upon the designs of Flickinger, Massenburg and McNeal in either semi or fully-parametric topology. In the late 1990s and in the 2000s, parametric equalizers became increasingly available as digital signal processing (DSP) equipment, usually in the form of plug-ins for various digital audio workstations. Standalone outboard gear versions of DSP parametric equalizers were also quickly introduced after
8904-402: The resistive element is connected to a terminal (E, G) on the case. The wiper is connected to a third terminal (F), usually between the other two. On panel potentiometers, the wiper is usually the center terminal of three. For single-turn potentiometers, this wiper typically travels just under one revolution around the contact. The only point of ingress for contamination is the narrow space between
9010-452: The response of microphones , instrument pickups , loudspeakers , and hall acoustics . Equalization may also be used to eliminate or reduce unwanted sounds (e.g., low-frequency hum coming from a guitar amplifier), make certain instruments or voices more (or less) prominent, enhance particular aspects of an instrument's tone, or combat feedback (howling) in a public address system. Equalizers are also used in music production to adjust
9116-428: The rotary versions range from 20 to 450 mm in diameter, with each having a height of 0.5 mm. Membrane potentiometers can be used for position sensing. For touch-screen devices using resistive technology, a two-dimensional membrane potentiometer provides x and y coordinates. The top layer is thin glass spaced close to a neighboring inner layer. The underside of the top layer has a transparent conductive coating;
9222-411: The same four-inch diameter, more akin to what one would find in a table radio. However, this speaker system is sold with an active equalizer. That equalizer must be inserted into the amplifier system so that the amplified signal that is finally sent to the speakers has its response increased at the frequencies where the response of these drivers falls off, and vice versa, producing the response intended by
9328-402: The shaft and the housing it rotates in. Another type is the linear slider potentiometer, which has a wiper which slides along a linear element instead of rotating. Contamination can potentially enter anywhere along the slot the slider moves in, making effective sealing more difficult and compromising long-term reliability. An advantage of the slider potentiometer is that the slider position gives
9434-439: The software versions. Although the range of equalization functions is governed by the theory of linear filters , the adjustment of those functions and the flexibility with which they can be adjusted varies according to the topology of the circuitry and controls presented to the user. Shelving controls are usually simple first-order filter functions that alter the relative gains between frequencies much higher and much lower than
9540-402: The sound quality of a recording studio in addition to its use in live sound reinforcement systems and even home hi-fi systems. During live events where signals from microphones are amplified and sent to speaker systems, equalization is not only used to "flatten" the frequency response but may also be useful in eliminating feedback . When the sound produced by the speakers is picked up by
9646-419: The stereo demultiplexer . In addition to adjusting the relative amplitude of frequency bands, an audio equalizer usually alters the relative phases of those frequencies. While the human ear is not as sensitive to the phase of audio frequencies, music professionals may favor certain equalizers because of how they affect the timbre of the musical content by way of audible phase artifacts. A high-pass filter
9752-450: The straight line nature of the physical sliding motion. The word linear when applied to a potentiometer regardless of being a slide or rotary type, describes a linear relationship of the pot's position versus the measured value of the pot's tap (wiper or electrical output) pin. Potentiometers were formerly used to control picture brightness, contrast, and color response. A potentiometer was often used to adjust "vertical hold", which affected
9858-468: The strict sense of the term. A parametric equalizer has one or more sections each of which implements a second-order filter function. This involves three adjustments: selection of the center frequency (in Hz ), adjustment of the Q which determines the sharpness of the bandwidth , and the level or gain control which determines how much those frequencies are boosted or cut relative to frequencies much above or below
9964-435: The surface of the layer beneath it has a transparent resistive coating. A finger or stylus deforms the glass to contact the underlying layer. Edges of the resistive layer have conductive contacts. Locating the contact point is done by applying a voltage to opposite edges, leaving the other two edges temporarily unconnected. The voltage of the top layer provides one coordinate. Disconnecting those two edges, and applying voltage to
10070-448: The synchronization between the receiver's internal sweep circuit (sometimes a multivibrator ) and the received picture signal, along with other things such as audio-video carrier offset, tuning frequency (for push-button sets) and so on. It also helps in frequency modulation of waves. Potentiometers can be used as position feedback devices in order to create closed-loop control , such as in a servomechanism . This method of motion control
10176-520: The three primary parameters: amplitude , center frequency and bandwidth . The amplitude of each band can be controlled, and the center frequency can be shifted, and the bandwidth (which is inversely related to " Q ") can be widened or narrowed. Parametric equalizers are capable of making much more precise adjustments to the sound than other equalizers, and are commonly used in sound recording and live sound reinforcement . Parametric equalizers are also sold as standalone outboard gear units. A variant of
10282-448: The treble control increases f p and decreases f z so that frequencies higher than f z are boosted. Setting the treble control at the center sets f z = f p so that | H ( f )| = 1 and the circuit has no effect. At most, the slope of the filter response in the transition region will be 6 dB per octave. Similarly the response of a low shelf or bass control can be represented as: In this case,
10388-426: The turns of resistance wire. The "fingers" can be moved along the coil of resistance wire by a sliding knob thus changing the "tapping" point. Wire-wound rheostats made with ratings up to several thousand watts are used in applications such as DC motor drives, electric welding controls, or in the controls for generators. The rating of the rheostat is given with the full resistance value and the allowable power dissipation
10494-530: The two ends of the potentiometer. This is their most common use. The voltage across R L can be calculated by: V L = R 2 R L R 1 R L + R 2 R L + R 1 R 2 ⋅ V s . {\displaystyle V_{\mathrm {L} }={R_{2}R_{\mathrm {L} } \over R_{1}R_{\mathrm {L} }+R_{2}R_{\mathrm {L} }+R_{1}R_{2}}\cdot V_{s}.} If R L
10600-405: The uneven frequency response of an electric system by applying a filter having the opposite response, thus restoring the fidelity of the transmission . A plot of the system's net frequency response would be a flat line, as its response at any frequency would be equal to its response at any other frequency. Hence the term equalization . Later the concept was applied in audio engineering to adjust
10706-448: The user. However, in bi-amplification , these filters operate on the low level audio signals, sending the low-frequency and high-frequency signal components to separate amplifiers, which connect to the woofers and tweeters, respectively. Equalization is used in a reciprocal manner in certain communication channels and recording technologies. The original music is passed through a particular filter to alter its frequency balance, followed by
10812-450: The volume increased by turning the same knob. Multiple resistance elements can be ganged together with their sliding contacts on the same shaft, for example in stereo audio amplifiers for volume control. In other applications, such as domestic light dimmers , the normal usage pattern is best satisfied if the potentiometer remains set at its current position, so the switch is operated by a push action, alternately on and off, by axial presses of
10918-409: The wiper. Where the rheostat must be rated for higher power (more than about 1 watt), it may be built with a resistance wire wound around a semi-circular insulator, with the wiper sliding from one turn of the wire to the next. Sometimes a rheostat is made from resistance wire wound on a heat-resisting cylinder, with the slider made from a number of metal fingers that grip lightly onto a small portion of
11024-508: Was first used by John Volkman working at RCA in the 1920s. That system was used to equalize a motion picture theater sound playback system. The Langevin Model EQ-251A was the first equalizer to use slide controls. It featured two passive equalization sections, a bass shelving filter, and a pass band filter. Each filter had switchable frequencies and used a 15-position slide switch to adjust cut or boost. The first true graphic equalizer
11130-588: Was stolen after the first concert at the Queen Elizabeth Hall in London, England. A second was built for the concert at the Royal Festival Hall in London on 14 April 1969. It had two pan pots and four channels. Lost for many years, it was found under the aegis of London's Victoria and Albert Museum , and displayed as part of their Theatre Collections gallery from March 2009. It is also included as part of
11236-559: Was the type 7080 developed by Art Davis 's Cinema Engineering . It featured 6 bands with a boost or cut range of 8 dB . It used a slide switch to adjust each band in 1 dB steps. Davis's second graphic equalizer was the Altec Lansing Model 9062A EQ. In 1967 Davis developed the first 1/3 octave variable notch filter set, the Altec-Lansing "Acousta-Voice" system. In 1966, Burgess Macneal and George Massenburg envisioned
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