A humbucker (or Humbucking pickup) is a type of electric guitar pickup, first patented by Seth Lover and the Gibson company, that uses two coils, both generating string signal. Humbuckers have higher output than a single coil pickup since both coils are connected in series. Like a single coil pickup, the magnets in a humbucker produce a magnetic field around the strings, which in turn induces an electrical current in the coils as the strings vibrate. A humbucking pickup is essentially two single coil pickups, one of which has the north poles of its pole pieces oriented toward the strings, and the other has the south pole of its pole pieces oriented toward the strings. Since the coils are connected in series and out of phase, noise and interference are significantly reduced via common-mode rejection. Humbuckers get their name from the fact that they cancel out the interference (they "buck the hum") induced by alternating current, which is normally experienced with single coil pickups.
Hum is the result of the alternating magnetic fields typically created by transformers and power supplies inside various electrical equipment utilizing alternating current. As these alternating magnetic fields pass through the pickup coil, they induce an alternating current in the coil. The magnetic field may be very weak at the pickup, but once the signal is put through various pedals and amps it can become much more evident. Using a guitar without humbuckers, a musician would hear a slight but noticeable hum from the amp in silent sections of the music. Sources of hum generated in the studio and on stage can include high-power amps, processors, mixers, motors, power lines, and other sources. Humbuckers dramatically reduce the hum effect compared to single coil pickups.
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The "humbucking coil" was invented in 1934 by Electro-Voice, an American professional audio company based in South Bend, Indiana that Al Kahn and Lou Burroughs incorporated in 1930 for the purpose of manufacturing portable public address equipment, including microphones and loudspeakers.[1]
A successful early humbucking pickup was the so-called PAF (literally "Patent Applied For") invented by Seth Lover, a Gibson employee, in 1955.[2] Because of this, and because of its use on the Gibson Les Paul guitar, the humbucker is strongly associated with Gibson, although humbuckers have been used in many different guitar designs by many different manufacturers. Humbuckers are also known as dual-coil, double-coil, or hum-canceling pickups. Rickenbacker offered dual coil pickups arranged in a humbucking pattern beginning in late 1953 but dropped the design in 1954 due to the perceived distorted sound. The Gibson Les Paul was the first guitar to use humbuckers in substantial production, but since then, even some models of Fender Stratocasters and Telecasters, traditionally fitted with single-coil pickups, are factory-equipped with humbuckers. Stratocasters fitted with one humbucker in the bridge position, resulting in a pickup configuration noted as H-S-S (starting at bridge pickup: H for humbucker, S for single coil) are referred to as "Fat Strats", because of the "fatter", "rounder" tone offered by the humbucking pickup.
In any magnetic pickup, a vibrating oft-magnetic guitar string induces an alternating current in its coil(s). However, magnetic coils also make excellent antennae and are therefore sensitive to electromagnetic interference caused by mains wiring (mains hum) and electrical appliances like transformers, motors, and computer screens. Guitar pickups rebroadcast this noise, which can be quite audible, sounding like a constant hum or buzz.
A humbucker has two coils with opposing windings and polarities. The string motion induces current in both coils in the same direction, since the reverse winding and reversed phase of one coil create a signal in the same direction as the other coil. Electromagnetic interference, on the other hand, induces current in opposing directions in each coil because it is only sensitive to the winding direction, which is reversed for one coil. When the signals from both pickups are summed together, the noise is cancelled due to destructive interference, while the actual signal is increased due to constructive interference, thus dramatically improving the signal-to-noise ratio. This technique is called common-mode rejection by electrical engineers, and is also used in balanced lines in audio recording.
Solid-body guitars, such as Fender Stratocasters, usually feature cavities only for single-coil pickups. Installing full-sized humbuckers requires additional routing of the woodwork and cutting of the pickguard (if the instrument has a pickguard). If the process is not carefully done, the instrument's body and pickguard may be damaged. For most guitarists, this is unacceptable; especially for expensive vintage guitars where it is vital to preserve cosmetic appearance. As a result, many pickup manufacturers now produce humbucking pickups compacted into the size of a single coil, accomplished by vertically "stacking" the coils instead of placing them side-by-side as in a regular humbucker. Many different kinds of stacked humbuckers are available from several manufacturers, producing a wide range of different tones.
Another design known as rail humbuckers divides a single coil-size pickup in half lengthwise, and the windings are wound around two pole pieces, typically resembling a rail. These pickups look like a normal, albeit smaller, humbucker. This, however, is typically used in conjunction with stacked humbuckers, to produce a high-output pickup. This design can also extend to a "quadrail", by using a rail humbucker for each "single coil" of a normal humbucker.
The same type of rails can also be found in a normal-size humbucker, however. Heavy metal guitarist Dimebag Darrell made heavy use of this type of pickup wired in the bridge position. These tend to also sound fuller and have a higher output and attack than the single coil-size version.
Some guitars which have humbucking pickups feature "coil splits", which allow the pickups to act as "pseudo-single" coils by either short-circuiting or bypassing one coil. The electrical circuit of the pickup is reduced to that of a true single coil so there is no hum canceling effect. Usually, this feature is activated using a miniature toggle switch or a DPDT push-pull switch mounted on a potentiometer. Some guitars (e.g. the Peavey T-60 and the Fender Classic Player Jaguar HH) make use of a variable coil split circuit that allows the guitarist to dial a variable amount of signal from the second coil, from pure single-coil to full humbucker and everything in-between.
Coil splits are often wrongly referred to as a "coil tap". Coil taps are most commonly found on single coil pickups, and involve an extra hook-up wire being included during the manufacture of the pickup so the guitarist can choose to have all the windings of the pickup included in the circuit, for a fatter, higher output sound with more midrange; or switch the output to "Tap" into the windings at a point that is less than the full coil for a brighter, lower output, cleaner sound. By example: a full pickup coil may be 10,000 turns of wire and the "Tap" may be at 8000 turns. Because of the confusion between coil splits and coil taps - and the rareness of coil taps in general - it is difficult to find tappable single coil pickups for sale. However, pickup manufacturer Seymour Duncan offers tapped versions of many of their Telecaster and Stratocaster pickups on their website at an increased cost.
While the original humbucker remains the most common noise-reducing pickup design, inventors have tried many other approaches to reducing noise in guitar pickups.
Many instruments will use a combination of separate single coil pickups in a hum reducing configuration, where the magnetic polarity is different and the coils are electrically reversed. This arrangement is similar to that of a humbucking pickup and noise is effectively reduced. Some examples of this are the Fender Jazz Bass, introduced in 1960, which has used a pair of single coil pickups, one near the bridge and another one about half way between the bridge and the neck, and many Stratocaster style guitars, which often have 3 pickups with the middle one reversed electrically and magnetically. The (usually) 5-way selector switch allows 2 humbucking settings, where the reversed middle pickup is used in parallel with either the bridge or neck pickup.
In 1957, Fender introduced a split pickup to its Precision Bass, which was wired in humbucking fashion, with one coil serving the E and A strings, the other the D and G strings. Both coils pick up the same noise, but since each string is only served by one coil, a single-coil sound is provided. The concept of this later expanded to G&L's Z-coil pickup, which is used for standard guitars.
In 1985, Lace Music Products introduced the Lace Sensor pickups, which utilize a proprietary hum-screening technique to eliminate noise while preserving single-coil tone.
In 1996, Kinman Guitar Electrix introduced replacement pickups for Stratocaster and Telecaster based on a differential coil technology, essentially a stacked humbucker where the lower pickup coil functions solely as a noise sensing coil, while only the upper pickup coil is able to sense the string vibrations. This was achieved by the use of magnetic shields augmented by differential coils. These pickups are of the single pole type often referred to as single coils. In mid 2011 Kinman released a range of innovative side-by-side humbuckers which incorporate new Patent Applied For technology. Kinman claim their new humbuckers have greater dynamic range and increased clarity compared to conventional humbuckers. [3]