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Apickup is an electronic device that converts energy from one form to another that captures or senses mechanical vibrations produced bymusical instruments, particularlystringed instruments such as theelectric guitar, and converts these to an electrical signal that isamplified using aninstrument amplifier to produce musical sounds through aloudspeaker in aspeaker enclosure. The signal from a pickup can also berecorded directly.
The first electrical string instrument with pickups, the "Frying Pan" slide guitar, was created byGeorge Beauchamp andAdolph Rickenbacker around 1931.[1]
Most electric guitars and electric basses usemagnetic pickups.Acoustic guitars,upright basses andfiddles often use apiezo electric pickup.[citation needed]
A typical magnetic pickup is a transducer (specifically avariable reluctance sensor) that consists of one or morepermanent magnets (usuallyalnico orferrite) wrapped with a coil of several thousand turns of fine enameledcopper coil. The magnet creates amagnetic field which is focused by the pickup'spole piece or pieces.[2] The permanent magnet in the pickup magnetizes the guitar string above it. This causes the string to generate a magnetic field which is in alignment with that of the permanent magnet. When the string is plucked, the magnetic field around it moves up and down with the string. This moving magnetic field induces a voltage in the coil of the pickup as described byFaraday's law of induction.[3] Output voltage depends on the instrument and playing style and which string(s) are played and where on the string, but for example, aSamickTV Twenty guitar played on the bridge measured 16 mV RMS (200 mV peak) for one string and 128 mV RMS (850 mV peak) for a chord.[4]
The pickup is connected with a6.35 mm audio jack (instrument cable) to anamplifier, which amplifies the signal to a sufficient magnitude of power to drive aloudspeaker (most amplifiers are above 10 watts). A pickup can also be connected torecording equipment via a patch cable.
A pickup is a part of an electric guitar or bass that "hears" the strings and turns their vibrations into sound. It’s usually attached to the guitar's body, but sometimes it’s placed on other parts like the bridge (where the strings rest) or the neck.
Pickups come in different types:
The pickup plays a big role in how the guitar sounds, and different guitars often use unique pickups to create their own signature tone. Guitar companies use this as a key feature to attract buyers.
Pickups have magnetic polepieces, typically one or two for each string, with the notable exceptions of rail andlipstick tube pickups. Single polepieces are approximately centered on each string whereas dual polepieces such as the standard pickups on theFender Jazz Bass andPrecision Bass sit either side of each string.
On most guitars, the strings are not fully parallel: they converge at the nut and diverge at the bridge. Thus, bridge, neck and middle pickups usually have different polepiece spacings on the same guitar.
There are several standards on pickup sizes and string spacing between the poles. Spacing is measured either as a distance between 1st to 6th polepieces' centers (this is also called "E-to-E" spacing), or as a distance between adjacent polepieces' centers.
| 1st-to-6th | Adjacent | |
|---|---|---|
| Standard spacing (Vintage Gibson guitars) | 1.90" 48 mm | 0.380" 9.6 mm |
| F-spacing (Most Fender guitars, modern Gibson,Floyd Rose bridges) | 2.01" 51 mm | 0.402" 10.2 mm |
| Very close to bridge, extra pickup (Roland GK series hexaphonic) | 2.060" 52.3 mm | 0.412" 10.5 mm |
| Telecaster spacing (Fender Telecaster guitars) | 2.165" 55 mm | 0.433" 11 mm |
| Steinberger Spirit GT-Pro spacing (may be typical for other Steinberger guitars) | 2.362" 60 mm | 0.3937" 10 mm |
Some high-output pickups employ very strong magnets, thus creating more flux and thereby more output. This can be detrimental to the final sound because the magnet's pull on the strings (called string capture[5]) can cause problems with intonation as well asdamp the strings and reducesustain.
Other high-output pickups have more turns of wire to increase the voltage generated by the string's movement. However, this also increases the pickup's outputresistance andimpedance, which can affect high frequencies if the pickup is not isolated by abuffer amplifier or aDI unit.
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The turns of wire in proximity to each other have an equivalent self-capacitance that, when added to any cable capacitance present, resonates with theinductance of the winding. Thisresonance can accentuate certain frequencies, giving the pickup a characteristic tonal quality. The more turns of wire in the winding, the higher the output voltage[6] but the lower thisresonance frequency.
The arrangement of parasitic resistances and capacitances in the guitar, cable, and amplifier input, combined with the inductivesource impedance inherent in this type oftransducer forms a resistively-damped second-orderlow-passfilter, producing a non-linearity effect not found in piezoelectric or optical transducers. Pickups are usually designed to feed a highinput impedance, typically amegohm or more, and a low-impedance load increases attenuation of higher frequencies. Typical maximum frequency of a single-coil pickup is around 5 kHz, with the highest note on a typical guitar fretboard having a fundamental frequency of 1.17 kHz.
Single-coil pickups act like a directional antenna and are prone to pick upmains hum—nuisancealternating current electromagnetic interference from electrical power cables, power transformers, fluorescent light ballasts, video monitors or televisions—along with the musical signal. Mains hum consists of a fundamental signal at a nominal 50 or 60 Hz, depending on local current frequency, and usually some harmonic content.
To overcome this, thehumbucking pickup was invented byJoseph Raymond "Ray" Butts (forGretsch), whileSeth Lover also worked on one forGibson.[7] Who developed it first is a matter of some debate, but Butts was awarded the first patent (U.S. patent 2,892,371) and Lover came next (U.S. patent 2,896,491).
A humbucking pickup is composed of two coils, with each coil wound reverse to the other. Each set of six magnetic poles is also opposite in polarity. Since ambient hum from electrical devices reaches the coils ascommon-mode noise, it induces an equal voltage in each coil, but 180 degrees out of phase between the two voltages. These effectively cancel each other, while the signal from the guitar string is doubled.
When wired in series, as is most common, the overallinductance of the pickup is increased, which lowers its resonance frequency and attenuates the higher frequencies, giving a less trebly tone (i.e., "fatter") than either of the two component single-coil pickups would give alone.
An alternative wiring places the coils inbuck parallel, which has a more neutral effect on resonant frequency. This pickup wiring is rare,[8] as guitarists have come to expect that humbucking pickups 'have a sound', and are not so neutral. On fine jazz guitars, the parallel wiring produces significantly cleaner sound,[8] as the lowered source impedance drives capacitive cable with lower high frequency attenuation.
Aside-by-side humbucking pickup senses a wider section of each string than a single-coil pickup.[9] By picking up a larger portion of the vibrating string, more lower harmonics are present in the signal produced by the pickup in relation to high harmonics, resulting in a "fatter" tone. Humbucking pickups in the narrow form factor of a single coil, designed to replace single-coil pickups, have the narrower aperture resembling that of a single coil pickup. Some models of these single-coil-replacement humbuckers produce more authentic resemblances to classic single-coil tones than full-size humbucking pickups of a similar inductance.
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Most electric guitars have two or three magnetic pickups. A combination of pickups is called apickup configuration, usually notated by writing out the pickup types in order from bridge pickup through mid pickup(s) to neck pickup, using "S" for single-coil and "H" for humbucker. Typically the bridge pickup is known as the lead pickup, and the neck pickup is known as the rhythm pickup.[10]
Common pickup configurations include:
Less frequently found configurations are:
Examples of rare configurations that only a few particular models use include:
The piezoelectric pickup contains a piezo crystal, which converts the vibrations directly to a changing voltage.
Manysemi-acoustic andacoustic guitars, and some electric guitars and basses, have been fitted withpiezoelectric pickups instead of, or in addition to, magnetic pickups. These have a very different sound, and also have the advantage of not picking up any other magnetic fields, such as mains hum andfeedback from monitoring loops. Inhybrid guitars, this system allows switching between magnetic pickup and piezo sounds, or simultaneously blending the output. Solid bodied guitars with only a piezo pickup are known assilent guitars, which are usually used for practicing by acoustic guitarists. Piezo pickups can also be built intoelectric guitar bridges for conversion of existing instruments.
Most pickups for bowed string instruments, such as cello, violin, and double bass, are piezoelectric. These may be inlaid into thebridge, laid between the bridge feet and the top of the instrument, or, less frequently, wedged under a wing of the bridge. Some pickups are fastened to the top of the instrument with removableputty.
Piezoelectric pickups have a very highoutput impedance and appear as acapacitance in series with avoltage source. They therefore often have an instrument-mountedbuffer amplifier fitted to maximizefrequency response.
The piezo pickup gives a very wide frequency range output compared to the magnetic types and can give largeamplitude signals from the strings. For this reason, the buffer amplifier is often powered from relatively high voltage rails (about ±9 V) to avoiddistortion due toclipping. A less linearpreamp (like a single-FET amplifier) might be preferable due to softer clipping characteristics.[11] Such an amplifier starts to distort sooner, which makes the distortion less"buzzy" and less audible than a more linear, but less forgivingop-amp.[citation needed] However, at least one study[12] indicates that most people cannot tell the difference between FET and op-amp circuits in blind listening comparisons of electric instrument preamps, which correlates with results of formal studies of other types of audio devices. Sometimes, piezoelectric pickups are used in conjunction with magnetic types to give a wider range of available sounds.
For early pickup devices using the piezoelectric effect, seephonograph.
Some pickup products are installed and used similarly to piezoelectric pickups, but use different underlying technology, for instanceelectret[13] orcondenser microphone technology.[14]
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There are basically four principles used to convert sound into an alternating current, each with their pros and cons:
An amplification system with twotransducers combines the qualities of both. A combination of a microphone and a piezoelectric pickup typically produces better sound quality and less sensitivity to feedback, as compared to single transducers. However, this is not always the case. A less frequently used combination is a piezoelectric and a magnetic pickup. This combination can work well for a solid sound withdynamics and expression. Examples of a double system amplifier are the Highlander iP-2, the Verweij VAMP or the LR Baggs dual source and the D-TAR Multisource.[15]
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Hexaphonic pickups (also calleddivided pickups andpolyphonic pickups) have a separate output for each string (Hexaphonic assumes six strings, as on a guitar). This allows for separate processing and amplification for each string. It also allows a converter to sense the pitch coming from individual string signals for producing note commands, typically according to theMIDI (musical instrument digital interface) protocol. A hexaphonic pickup and a converter are usually components of aguitar/synthesizer.
Such pickups are uncommon (compared to normal ones), and only a few notable models exist, like the piezoelectric pickups on theMoog Guitar. Hexaphonic pickups can be either magnetic or piezoelectric or based on the condensor principle likeelectronicpickups
Optical pickups are a fairly recent development that work by sensing the interruption of a light beam by a vibrating string. The light source is usually an LED, and the detector is aphotodiode orphototransistor.[16] These pickups are completely resistant to magnetic or electric interference and also have a very broad and flat frequency response, unlike magnetic pickups.
Optical pickup guitars were first shown at the 1969NAMM Convention inChicago, by Ron Hoag.[17]
In 2000, Christopher Willcox, founder of LightWave Systems, unveiled a new beta technology for an optical pickup system using infrared light. In May 2001, LightWave Systems released their second generation pickup, dubbed the "S2."[18]
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Pickups can be eitheractive or passive. Pickups, apart from optical types, are inherently passive transducers. "Passive" pickups are usually wire-wound around a magnet, and are the most common type used. They can generateelectric potential without need for external power, though their output is relatively low, and the harmonic content of output depends greatly on the winding.
"Active" pickups incorporate electronic circuitry to modify the signal. Active circuits are able to filter, attenuate or boost the signal from the pickup. The main disadvantage of an active system is requirement of a battery power source to operate thepreamp circuitry. Batteries limit circuit design and functionality, in addition to being inconvenient to the musician. The circuitry may be as simple as a single transistor, or up to severaloperational amplifiers configured as active filters, activeEQ and other sound-shaping features. The op amps used must be of a low-power design to optimize battery life, a design restriction that limits the dynamic range of the circuit. The active circuitry may contain audio filters, which reduce the dynamic range and mildly distort certain ranges. High-output active pickup systems also have an effect on an amplifier's input circuit.
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Rickenbacker was the first manufacturer to market stereo instruments (guitars and basses). Their proprietary "Ric-O-Sound" circuitry has two separate output jacks, allowing the musician to send each pickup to its own audio chain (effects device, amplifier, mix console input).
Teisco produced a guitar with a stereo option.[19] Teisco divided the two sections in the upper three strings and the lower three strings for each individual output.
TheGittler guitar was a limited production guitar with six pickups, one for each string.
Gibson created the HD.6X Pro guitar that captures a separate signal for each individual string and sends them to an onboard analog/digital converter, then out of the guitar viaEthernet cable.
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