Your bass guitar’s choice of pickup can make a dramatic impactful statement about its tone: single-coil pickups often deliver brighter, funkier sound while humbuckers provide fuller and warmer tones.
Coil winding techniques have an even larger influence on a pickup’s sound; changing how a coil is wound can significantly alter its frequency response, clarity and output.
String Contact Area
Steel strings on your bass guitar act as magnetic bodies that, when vibrated by a pickup coil, cause an electric current to flow across it and change as your string vibrates, creating the sound you hear. Intricate patterns and harmonics generated during string vibration will also manifest themselves audibly; large coil pickups have more ability to capture these higher overtones for fuller sound while smaller coils tend to focus more closely on providing fundamental notes.
Coils may either be single coils that sense all strings individually, or dual-coil humbuckers with their magnetic polarities and winding direction reversed – the latter giving an advantage in terms of adding together signals from strings while cancelling out noise (mains hum).
Scatterwinding requires more time and skill, but can bring many advantages over machine-wound coils. Scatterwinding reduces distributed capacitance – the total sum of all individual turns of wire within close proximity – as well as amplifying specific frequencies or creating a unique tonal quality within a pickup.
Comparing single-coil pickups to humbuckers reveals an immediate distinction. A humbucking pickup consists of two coils joined in series or parallel (sometimes offered as switchable options e.g. on G&L L-series models) with each winding direction opposite to that of its neighbor coil, canceling out ambient noise that gets picked up by both coils while increasing output output by twofold.
Humbuckers can be so effective at counteracting mains hum that they may often serve as an effective replacement for single-coil pickups, though be wary as using one can reduce some clarity and top-end detail you would expect from single-coils; though ultimately it depends on personal taste, type of guitar/string combination used, musical context and musical preference.
Wire Gauge
The gauge of wire used to wind the coil can have an enormous influence on tone and feel. Typically, thinner wire filters out more high frequencies (capacitance), while thickness affects resistance levels – finding the optimal combination between resistance and capacitance can allow a pickup to perform optimally.
Windings themselves can be affected by various factors, including the type and magnets of coil used, as well as style and amount of solder used to connect it to its bobbin. Furthermore, how it is wound, including how many turns there are and metal used to wind it can have an immense effect on sound production; nickel tends to produce warmer tones while stainless steel gives sharper more focused tones.
Another factor affecting the sound of a pickup is the size of each gap between each turn of wire, or winding. This impacts feedback levels and dynamics; additionally, insulating materials used can have an effect; for example a Teflon-insulated coil provides greater resistance to heat than plastic hookup wire, making soldering much simpler with no fear of melting or charring during assembly.
There are three basic types of bass pickups; single coil, humbucker and split-coil. Single-coils consist of one coiled wire with magnetic pole pieces positioned beneath each string – this type of pickup is sometimes known as P/J pickups – aligned beneath them and often called “P and J pickups”. They offer an expansive spectrum of tones from bright and aggressive to warm and rich depending on magnet placement and spacing or what insulating material is chosen; typically they’ll be installed close to bridge so as to be heard across musical genres; in some cases such as Yamaha’s “BBNE2 Nathan East Signature Model basses” where two single-coils will coexist side by side in tandem such as in their neck position alongside two humbuckers (called P& J pickups).
Magnets
While copper wire coils in pickups are certainly key, it’s also worthwhile to look at their magnetic wraps as key factors of sound production. Magnets play an instrumental role in changing electromagnetic fields generated by string vibrations passing through, changing into electric current that affects tone of pickups directly.
Alnico and ceramic magnets are two popular choices used in pickups. Alnico magnets tend to provide greater clarity and high end cut while ceramic tends to deliver more bass and mids, depending on its unique blend of core ingredients.
As magnets alter the electromagnetic field, they interact with string vibrations to cause interference that results in audible hums on some guitars. Humbuckers use two coils to mitigate interference noise for an enhanced and warmer sound that many players prefer.
A humbucker can either be configured to have both coils ‘in series’, which allows all strings to be picked up simultaneously, or it can be “tapped”, meaning only one of its coils are used; though tapping does not offer the hum canceling properties associated with humbuckers, it still provides increased output for more powerful bass sounds.
Apart from magnet type, bobbin shape and pole piece length can also have an effect on a pickup’s sound. Shorter coils tend to produce cleaner tones while taller ones produce fuller tones with thicker overtones. Furthermore, the distance between top and bottom flats on bobbins or pole pieces may have an impactful impact on coil surface area which in turn determines their inductance value.
Magnet materials used in bobbins can have an immense influence on the tone of any pickup, as each offers unique strengths and weaknesses. Alnico 2 magnets offer a balanced blend of mids and trebles with moderate power – perfect for vintage single-coil pickups found on Fender Telecasters or Stratocasters or P90 pickups commonly fitted on Les Pauls. Seymour Duncan employs Alnico 2 in their Joe Bonamassa signature set as well as PAF Antiquity models among many other models.
Windings
Coil wire gives pickups their distinctive sound. Wound around magnets and polepiece screws, it creates a magnetic field that can be activated by each bass string’s vibration; altering this local magnetic field changes its intensity, stimulating coil to produce electric current.
A coil’s resonance frequency can be modified by altering its number and amount of turns, as well as its amount of twist in each turn, with this changing its tone and frequency of resonance. Sensitivity to magnetic fields may also be altered by tension on its wire, material of wrapping (including magnet size and polepiece shape and size), and tension applied when winding it onto magnets and polepieces.
Many different winding methods can be employed to produce different tones. For instance, thicker coils with tighter windings tend to produce warmer and thicker tones while thinner and looser ones often create brighter sounds with an open tone. Insulation forms such as Formvar and Plain Enamel offer vintage sounds, creating unique sounds of their own.
Pickups come with various winding configurations to provide more tonal options to the player. Traditional single-coil designs exist alongside more innovative humbuckers that use two double coils wired together in series to cancel out any hum. Humbuckers generally produce higher output than single-coils while creating full, rich tones by eliminating some higher frequencies.
Single-coils that have been overwound can produce a more aggressive tone with increased midrange growl, while underwound single-coils provide a smooth, balanced tone with plenty of punch. Fender Precision basses use split-coils which are double coils separated apart so as to cancel out hum while maintaining a balanced tone.
Test the DC resistance of a bass pickup by touching its probes with your volt-ohm meter to a section of coil wire that has been cut away (don’t cut). If the reading is very low, this could indicate shorts within its coil windings reducing output significantly and necessitating either rewinding or replacing altogether.