Resistance (ohms) can be an excellent indicator of pickup health and can also help compare similar materials – for instance, one PAF humbucker might measure 6.8 ohms while another has 9 ohms.
Resistance alone cannot determine tone when selecting a bass guitar pickup; other elements play an integral part.
Inductance
An instrument’s inductance is one of the primary contributors to its sound. Higher inductance will produce warmer tones with decreased output while low inductance will give more output and brighter sounds. To measure inductance accurately you need either an analog volt-ohm meter with needle pointer or digital meters that provide exact numerical readings; I personally prefer digital meters because they provide you with more data.
The inductance of a bass guitar pickup can be affected by several different elements, including its type of pole pieces, core material and cover material. Pole piece material plays a pivotal role in creating its magnetic field; therefore the more conductive its surface area is, the higher its contribution is towards inductance. CuNiFe pole piece materials tend to have moderate effects on inductance while steel has higher permeability rates that significantly boost it.
Temperature can also have an effect on inductance. A hot pickup has lower inductance due to vibrating atoms in copper wire vibrating more when heated, colliding more electrons, and creating resistance within its circuitry – thus decreasing inductance.
Capacitance also plays an important role in pickup inductance. While typically this factor is relatively minor – as most of its capacitance comes from cables and internal wiring – there may be exceptions; for instance if a dual-coil pickup contains opposite-polarity windings that cancel each other out due to signal cancellation.
All these factors can have an effect on a pickup’s inductance and alter its sound; typically more resistance leads to darker, warmer tones while less resistance yields brighter sounds with increased output and higher highs and lows. But it’s important to keep in mind that an ohm reading does not reveal everything: two identical pickups could both read identically on this scale; their tones and performances would still differ dramatically regardless of ohm readings alone.
Inductive Coupling
A pickup is an electromagnetic device that creates a magnetic field through which guitar strings pass. When one of your guitar strings is plucked, any disruption of this field translates to an electrical signal which travels from within your bass guitar’s coil of wire all the way back to its amplifier and produces sound. The strength of this signal depends on how much your strings affect its magnetic field; its effect can also be expressed as inductance.
If you want your pickup to feature more midrange and less highs and lows, increase its inductance. However, if you wish for increased output (i.e. more power), reduce its inductance instead.
As to the impact inductance has on a pickup’s tone, there is no simple answer. Inductance depends on numerous factors including how magnets and coils are assembled together as well as wire gauge and diameter sizes, winding patterns, contact metal components with magnets and winding patterns that create tension around these magnets – some of these factors might even have a positive effect on its resonant frequency, another key factor when it comes to sound creation by any given pickup.
As a general rule, increasing resistance will result in less lows and increased highs, due to it limiting how much current can flow through a circuit and effectively “bleeding off” high frequencies like capacitors would do. Many pickup builders strive for low resistance levels – although that doesn’t guarantee great midrange sound!
DC Resistance is just one factor that affects a pickup’s tone; it doesn’t tell us everything we need to know but can give a general idea of what to expect when purchasing one of these pickups.
Capacitance
As strings move through a guitar pickup’s coils, Faraday’s Law generates an inductive magnetic field around them due to Faraday’s Law’s Induced Current Principle (ICCP), creating what we refer to as capacitance (measured in picofets). Capacitance affects sound by changing how much of a magnetic flux change from string movement is converted to voltage across coil.
Electrical resistance and capacitance are often mistakenly seen as interchangeable terms, but they’re actually two distinct concepts. Resistance – measured in ohms or kilohms (K) – measures materials’ resistance to electrical current flowing through them. Resistance does not change with frequency as it consistently opposes any signal being played whether its low bass, midrange or high treble frequencies.
Capacitance is an inherently frequency-dependent property; its magnitude increases as frequency does while decreasing with voltage. When applied in parallel RLC circuits like a pickup, capacitance (C) rises with inductance L and falls as impedance approaches zero; its peak values determine how much voltage will be generated when changing magnetic fields arise. At its resonant peak point lies its resonant peak point where both C and L reach maximum values simultaneously – this determines how much voltage is produced when magnetic field changes take place simultaneously.
As many other factors determine how much resistance is produced by any particular bass guitar pickup, such as material and size of magnet, number of coil turns, wire gauge used to wind coils, location and shape of pole pieces etc. All these variables combine to produce the tone heard when playing; generally speaking more resistance produces less output and darker sounding tones while lower resistance yields higher output and brighter sounds; generally however resistance doesn’t provide us with as much insight into a pickup’s tone compared to other more useful measures when it comes to accurately characterising its tone compared to other elements describing its overall sound like tone such as location & shape of pole pieces etc.
Impedance
A guitar pickup generates a tiny voltage when vibrating strings press against coils surrounding a magnet, and that current travels down the strings to your amplifier and through its volume & tone pots. But this signal isn’t entirely pure – resistance (e.g. 6K Ohm value) and inductance are added in parallel, leading to impedance – a combination of resistance and capacitance which serves to block electricity flowing through its circuits.
Impedance can be a difficult concept to grasp, yet understanding its impact is crucial in working with pickups. An impedance measurement of your guitar pickup affects its transmission ability; one with the appropriate input impedance will emit crisp, clear sounds while one fed an inappropriate impedance may muddy them further and reduce tonal quality.
So how can we measure pickup impedance? There are various approaches, but the most reliable is using what’s known as a dummy load. This device combines capacitance and resistance in order to simulate an actual guitar cable with volume/tone pots, but other values may also be commonplace. A standard combination would include 470pF of capacitance and 200k ohms resistance as standard settings; other values are sometimes seen.
DC Resistance of Pickups is an often-cited metric to compare pickups. Unfortunately, this measurement doesn’t always represent their tonal outcomes as accurately due to numerous variables influencing it (temperature, wire lengths and diameters, turns per coil count, type of bobbins and Alnico magnets, etc).
As a general rule, higher ohm ratings generally translate to increased windings and increased output; however, this doesn’t tell the entire tale; frequency response curves demonstrate how each pickup converts frequencies into voltages. An example would be two Ironstone neck pickups that possess the same basic variables but differ by being wound with either 43-44 gauge wire and having more turns versus one being wrapped with 42 gauge wire with fewer turns.