A conventional 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 high output since both coils are in series and the magnetic circuit is low loss. Like a single coil pickup, a humbucker induces a slight magnetic field around the strings, which in turn induce an electrical current on the coils as the strings vibrate. The two coils have opposite polarity, opposite windings and are connected in series which causes noise and interference to be significantly reduced via common-mode rejection. Humbuckers get their name from their canceling out interference (they "buck the hum") induced by alternating current sources normally experienced with single coil pickups.

Hum is caused by interference typically created by transformers and power supplies inside various electrical equipment utilizing alternating current. As alternating current passes though a coil, it induces a magnetic field around 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 annoying 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.

History

The "humbucking coil" was invented in 1934 by Electro-Voice, a South Bend, Indiana-based professional audio company that Al Kahn and Lou Burroughs incorporated in 1930 for the purpose of manufacturing portable public address equipment, including microphones and loudspeakers.

A successful early humbucking pickup was the so-called PAF (literally "Patent Applied For") invented by Seth Lover, a Gibson employee, in 1955. 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.

How humbuckers work

In any magnetic pickup, a vibrating soft-magnetic guitar string induces an alternating current in its coil(s). However, magnetic coils also make excellent antennas and are therefore sensitive to electromagnetic interference caused by mains wiring (mains hum) and electrical appliances like transformers, motors, and computer screens. Guitar pickups pick up 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.

Sound

Using two coils also changes the tone of the pickup. The humbucking pickup produces a "warm" and "fat" tone that has been popularly associated with Les Pauls and SGs, in contrast to the "bright" or "clear" tone of the single coil pickups that are typically used on Fender guitars such as the Stratocaster and Telecaster. However, there are humbucking pickups that have a bright tone, similar to that of single-coil pickups.

Alternative humbucker designs

Stacked humbuckers

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 and possibly affect the tone produced by the body. 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.

Rail humbuckers

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 gain and attack than the single coil-size version.

Coil splits

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 while the magnetic circuit retains its original closed loop configuration. Usually, this feature is activated using a miniature toggle switch or push-pull switch on the tone 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 more 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; or some of the windings in use and some "tapped off" for a brighter, lower output, cleaner sound.

Notable humbucker designs

• Gibson "PAF" - Seth Lover's original humbucker design
• Fender Wide Range - Fender's first humbucker design, also by Seth Lover
• Gibson mini-humbucker - a smaller humbucker design used on the Gibson Firebird and Gibson Les Paul Deluxe
• Q-tuner: neodymium magnet humbuckers
• EMG Pickups - Active pickups since 1976
• Gretsch FilterTron - from 1957 to present; famously used on the Country Gentleman and other hollow-body guitars.

Other noise-reducing pickup designs

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 pickups 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.

See also

• Single coil
• Pick up

External links

• http://www.moore.org.au/pick001.htm Science and measurements behind electro-magnetic guitar pickups

References