Pickups are at the core of an electric bass’s tone. At its core, a guitar pickup consists of a magnet and coil of wire connected by pole pieces; when vibrating strings create magnetic fields around these components that create an electrical signal in the coil of wire that eventually leads back into an amplifier circuit.
Single Coil
There are various types of bass pickups, each offering their own distinctive sound. Popular examples are single-coil pickups (with one coil wrapped around a magnet), split coil, and dual coil (commonly known as humbuckers). With single coil pickups – single-coil basses have one wire coil wrapped around an oscillating magnet which creates an electrical current when vibrated strings hit it, transmitting that vibration back through to your amp via cable.
Single-coil pickups do have one disadvantage, however: they can pick up ambient noise that causes humming. This noise may come from things such as radio waves, computer monitors, or fluorescent lighting fixtures. There are ways to mitigate this problem though; for instance, using two single-coil pickups with volumes equal to each other will cancel out interference – something known as phase cancellation that’s why jazz basses come equipped with two rather than one single-coil pickup.
Another way of looking at this issue, as often articulated by pickup winders, guitarists, and gear enthusiasts in books or forum posts written about by pickup winding. This approach centers around the idea that when we pull on a string with magnetism (more about this shortly) its magnetic field changes shape which sends an electrical signal back to our pickups generating signal which goes to them via our guitar bridge pickup.
Simply stated, an instrument without magnets would produce much weaker signal output compared to one featuring magnets as their field lines would tend to move away from the string towards their pole pieces, producing much weaker output signals than their magnetized counterparts.
Considered from another angle, string as a source of magnetic flux can generate signals in pickups that ultimately are captured and converted by your guitar amplifiers. This perspective can be found in most technical publications by physicists, engineers and National High Magnetic Field Laboratory employees (however we pickup winders still don’t understand).
An alternative approach is combining features from both of these pickup types into the J bass pickup type, essentially an unconventional single-coil with four magnetic slugs–two for each string–strangely staggered so as to achieve maximum tonal range and balance.
Split Coil
Split coil bass pickups are one of the most widely-used styles, featuring two pickup coils with their own magnets connected in series to cancel out any hum-cancelling effects and produce different tonal options without dismantling and reconnecting coils for different styles of music. This gives bassists access to an expansive palette of tonal options.
Split coil pickups utilize vibrating strings that cause their magnetic field to change, altering current flowing through a coil and producing an audible signal transmitted from it directly into the bass guitar body and amplified. This style produces rich, full and warm tones with lots of clarity and definition – the signature sound that made the Gibson EB-bass so popular and still remains a favorite among bassists today.
As with the single coil, numerous factors including coil count and magnet type and pole pieces used can influence the tone of a split coil. Overwound splits tend to feature more midrange growl while their underwound counterparts often produce cleaner sound with less muddy tones.
Single-coil pickups suffer from one key drawback: they’re susceptible to picking up mains hum, an annoying 50 or 60 Hz electrical interference found in most homes from power transformers, fluorescent light ballasts and video monitors. A single-coil pickup acts like a directional antenna; as such it was developed by Joseph Raymond Butts and Seth Lover at Gretsch Guitar Company and later adopted by Gibson Guitar Company to combat mains hum.
Humbucking pickups consist of two single coils wired together and stacked, with their magnetic fields aligned across from one another and in parallel wiring; their respective magnetic fields canceling out one another to eliminate mains hum and produce thicker midrange tone – an approach popular among modern bass pickup manufacturers such as DiMarzio, Fender Noiseless and EMG.
Humbucker
There are various kinds of bass pickups, each working differently. But most utilize magnets to detect magnetic fields produced by strings and convert them to electricity that can then be amplified and amplified – producing sound signals which help define your tone.
Humbucking units are one of the most widely-used bass pickups, featuring two coils with opposite polarities to cancel out noise and boost output while maintaining that rich, full sound prized by bassists worldwide. Furthermore, these pickups can effectively eliminate mains humming caused by interference caused by constant current running through electrical power lines, fluorescent light ballasts or any other sources of electromagnetic interference.
Humbuckers are dual-coil pickups with opposing polarities in their pole pieces – the small metal inserts protruding from each coil of wire (see photo). They are often wound on a bobbin made of any material capable of carrying thousands of turns of copper wire; polycarbonate and butyrate plastic bobbins are popular, as is butyrate which Seymour Duncan prefers in order to honor Gibson’s process in Kalamazoo during the 1950s.
Humbucker pickups feature two coils that can either be connected in series (traditional configuration), or parallel, so as to produce hotter and more powerful signals than from single-coil pickups. They may also be “tapped”, in which only one coil emits sound through the guitar body – creating an effect closer to that of two single-coil pickups being used together.
Fender introduced split-coil humbuckers for its Precision basses in 1957, and this type of pickup serves E and A strings while D and G strings receive their own coil. By splitting their magnetic fields apart, both coils see nearly identical electromagnetic disturbances that cancel each other out when split apart.
Custom Shop
Bass guitar pickups are electromagnets designed to transform string vibrations into electrical energy that can be amplified into distinctive tones. Usually composed of copper wire coils wrapped around one or more magnets and polepiece screws to form the magnetic field necessary to detect string vibration. As strings vibrate above them, their changing magnetic fields alter, motivating the coils’ copper wire coils to generate current which is picked up by the pickup and transformed into electric signals which are passed through a preamp before finally being transformed into audible audio signals that can be heard by players.
Different pickup designs produce very distinct sounds, some more suitable to specific genres than others. P, J and humbucker bass pickup types are among the most widely-used; P is most frequently seen being used (and some even multiple!) while J pickups may also feature prominently; you’ll hear their use in bass rock by Mike Dirnt of Green Day and Nate Mendel of Foo Fighters as well as fundamental funk from James Jamerson/Parliament as well as country lines by Billy “Bass” Nelson!
Other bass pickups may be less common but still helpful, including active bass pickups, split/split-coil and stacked humbucker pickups. Active bass guitar pickups use battery power and offer the capability of increasing or decreasing coil sensitivity according to your needs. Furthermore, active pickups permit bassists to control polarity of their pickup for optimal tones from their instrument.
Verifying the polarity of your bass guitar pickups before playing them for the first time is an easy yet often neglected step that could save a great deal of heartache later! Checking this before starting to play will pay dividends!