Pickup (music technology)

The first electrical string instrument with pickups, the "Frying Pan" slide guitar, was created by George Beauchamp and Adolph Rickenbacker around 1931.

Most electric guitars and electric basses use magnetic pickups. Acoustic guitars, upright basses, and fiddles often use piezoelectric pickups.

Magnetic pickups

A typical magnetic pickup is a transducer (specifically a variable reluctance sensor) that consists of one or more permanent magnets (usually alnico or ferrite) wrapped with a coil of several thousand turns of fine enameled copper wire. The magnet creates a magnetic field which is focused by the pickup's pole piece or pieces. 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 by Faraday's law of induction. Output voltage depends on the instrument and playing style and which string(s) are played and where on the string, but for example, a Samick TV 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.

The pickup is connected with a 6.35 mm audio jack (instrument cable) to an amplifier, which amplifies the signal to a sufficient magnitude of power to drive a loudspeaker (most amplifiers are above 10 watts). A pickup can also be connected to recording 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 an electrical signal. 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 several types:

• Single-coil pickups: One coil "listens" to all the strings.
• Humbuckers: Two coils work together to reduce noise and give a thicker sound.
• Split-coil pickups: Found on certain bass guitars, these have two separate coils, each "listening" to different strings. For example, on a bass with four strings, one coil handles the lower two strings, and the other handles the higher two.

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.

Construction

Pickups have magnetic polepieces, typically one or two for each string, with the notable exceptions of rail and lipstick tube pickups. Single polepieces are approximately centered on each string whereas dual polepieces such as the standard pickups on the Fender Jazz Bass and Precision 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.

Output

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) can cause problems with intonation as well as damp the strings and reduce sustain.

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 output resistance and impedance, which can affect high frequencies if the pickup is not isolated by a buffer amplifier or a DI unit.

Pickup sound

The turns of wire in proximity to each other have an equivalent self-capacitance that, when added to any cable capacitance present, resonates with the inductance of the winding. This resonance can accentuate certain frequencies, giving the pickup a characteristic tonal quality. The more turns of wire in the winding, the higher the output voltage but the lower this resonance frequency.

The arrangement of parasitic resistances and capacitances in the guitar, cable, and amplifier input, combined with the inductive source impedance inherent in this type of transducer forms a resistively-damped second-order low-pass filter, producing a non-linearity effect not found in piezoelectric or optical transducers. Pickups are usually designed to feed a high input impedance, typically a megohm 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.

Humbuckers

Single-coil pickups act like a directional antenna and are prone to pick up mains hum—nuisance alternating 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, the humbucking pickup was invented by Joseph Raymond "Ray" Butts (for Gretsch), while Seth Lover also worked on one for Gibson. 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 as common-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 overall inductance 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 in buck parallel, which has a more neutral effect on resonant frequency. This pickup wiring is rare, 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, as the lowered source impedance drives capacitive cable with lower high frequency attenuation. It is not uncommon for instruments aimed at rock players to have series/parallel switching between the two configurations.

A side-by-side humbucking pickup senses a wider section of each string than a single-coil pickup. 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.

Notation

Most electric guitars have two or three magnetic pickups. A combination of pickups is called a pickup 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.

Common pickup configurations include:

• H-H (Gibson Les Paul, many others including superstrats)

Less frequently found configurations are:

• S (Fender Esquire, early Gibson Les Paul Juniors, Gibson Melody Maker, Danelectro U1, some Telecasters)
• H (Gibson ES-165 Herb Ellis, Kramer Baretta, later Les Paul Juniors)
• H-S (Hamer Californian Deluxe, Les Paul BFG, Squier '51)
• H-H-H (some Gibson Les Paul Goldtop and Custom models, Gibson SG-3, Gibson ES-5 Switchmaster (after 1957), Kramer Jersey Star, Ibanez Destroyer, Ibanez PGM200)

Examples of rare configurations that only a few particular models use include:

• H-S, but with single-coil in the middle (one model of Fender Jazzmaster, Ibanez RG2011SC, Fender Player Jaguar)
• H-S-S, but with no space between the middle single-coil and the bridge humbucker (Hamer Phantom with angled neck pickup)
• H-H-S (Mayones Legend “22” Anders Nyström signature, some ESP Stephen Carpenter Models, and Alembic Jerry Garcia Models)
• H-S-S-H (Music Man Steve Morse Signature)
• S-H (some Telecasters, Music Man "Valentine" James Valentine signature)
• S-H-H (some early seven-string ESP Horizons)
• S-H-S (Fender Wayne Kramer Signature)