Resistance (ohm reading) alone does not determine a pickup’s output; other factors, like wire gauge and bobbin size can have more of an effect than resistance reading alone.
Other variables that determine a pickup’s tone include its number of coil windings, magnet strength/material/gauge combination and wire gauge. Let’s examine these further.
Number of Windings
Resistance is often one of the first specs people assume they understand when considering pickups; it serves as an entryway into learning how other specs affect tone, while giving an indication of general output level. However, resistance should only ever be viewed as part of the total picture and never as an end goal in itself.
Simply, coil turns dictate how difficult it is for electrons to travel from one end of a coil to the other and thus influences how loud/hot a pickup will sound.
Coil wire thickness can also play a key role in sound design. Thinner coil wire has higher resistance readings, leading to different tones from thin and thick wire pickups. A thicker gauge allows more parallel windings on a bobbin which lowers resistance while increasing capacitance; some players prefer thicker gauge wire’s sturdy sound while thin wire may provide more transparent tones.
Single-coil bass guitar pickups typically feature between 8,000 and 15,000 coil turns; early Gibson PAF models even had this practice, though this practice has since fallen out of fashion.
Volt-ohm meters provide an accurate reading when comparing two pickups with equal coil turns; however, the actual ohm reading will vary due to several factors including temperature. When the pickup is warmer, its ohm readings will rise while when cooler they will decrease.
As such, it’s vital that you read through a guitar or bass pickup’s full specification sheet before drawing any definitive conclusions about its suitability. Ohms only give an approximate idea of their resistance, so when trying to compare two pickups side-by-side to see which might be “better,” ohm reading alone won’t tell you much!
Magnets
Magnets in a guitar pickup give it its ability to convert vibrations of bass strings into an electrical signal that can be amplified. Pickups can also be placed strategically within a bass’ body to achieve different tones; each magnet in an electromagnet wrapped with copper wire has a specific magnetic field which becomes disturbed when vibrated strings disturb its magnetic field, creating small fluctuations in electric current flowing through its coil; this electric current then produces sound when played, producing its unique tone and sound of bass guitar playing!
The number of windings in a pickup’s coil is an integral component in its output, typically leading to lower DC resistance and greater output. Furthermore, how these windings are arranged within the coil as well as length and material choice of its construction all play major roles.
Another factor that can significantly influence a pickup’s output is its core. A larger core will allow closer proximity between strings and pickup, leading to more intense vibration of strings that push an amplifier harder, leading to overdrive or distortion effects in their sound.
Smaller cores will find it more difficult to approach the strings directly, leaving the strings feeling lighter with reduced sustain and brighter tones.
There are various factors that affect DC resistance, but it’s important to remember that DC resistance doesn’t reveal exactly how loud a particular pickup will be. To accurately assess its output level, one needs to know all aspects of its design including windings count, layout of magnets and type/strength and bobbin size of magnets used.
As a rule of thumb, two pickups with equal windings and construction will have similar output levels. Resistance measures only part of their total resistance so this measurement shouldn’t be relied upon alone when making comparisons between pickups.
Coil Wire
The coil wire of a guitar pickup is one of the main factors affecting its output. A larger diameter wire will have less resistance than smaller gauge wire, and depending on which material was used as insulation can also have an effect; for instance, using heavy formvar insulation instead of poly insulation results in increased output from such pickups.
The number of coil turns in a pickup can have an enormous impact on its sound. More turns create more magnetic field which in turn produces stronger electrical signal that travels up the strings; this signal can then be amplified within the guitar or bass itself.
High-output pickups tend to feature more coil turns; however, this doesn’t automatically equate to louder sound; rather it affects its frequency response and narrower bandwidth and tone.
Understanding pickups requires knowing that a magnet with coil wire creates a magnetic field around itself and the coil of wire, and when strings vibrate within this magnetic field electrons jump from end of coil to end resulting in an electric current that can be detected by an amplifier.
To measure the DC resistance of a guitar pickup, you can use a volt-ohm meter. These meters come both analog (with movable pointer) and digital versions that give precise numerical readings; when testing ohms by different methods may influence each reading differently so always pay close attention when comparing results.
An ohm reading doesn’t tell the whole story about a pickup, and even the most comprehensive specs sheet can only give you half of the information necessary to compare two pickups effectively (it would include aspects such as orientation/layout of magnets, magnet strength, coil wire diameter and number of turns, as well as number of turns). For best results when it comes to finding out how “hot” a pickup really is, simply play it yourself and listen for yourself!
Coil Joints
Coil joints can often go overlooked, yet are equally as critical to the performance of your guitar amp as its windings and magnets. Loose coil joints will result in buzzing or howling sounds that could indicate microphonic pickup – where loose coil windings vibrate when audio frequencies pass through them and are picked up by its speaker system.
If your bass features microphonic pickups, first check that the solder joints on its coils are tight and secure. If that does not solve it, remove your pickups and use a multimeter to test them for DC resistance; if that value is high it could indicate a solder joint which needs resoldering.
Many people often mistake the correlation between DC resistance and output: higher DC resistance means hotter sounding pickup. Not entirely true! DC resistance simply indicates how difficult it is for current to pass through coils, not whether or not its sounds hot. That depends on numerous other factors including magnets, bobbin materials and coil wire gauge.
Temperature can also affect DC resistance. A truck that has been left exposed to direct sunlight or stored in an overly-warm environment will have higher readings for DC resistance compared to one kept cool and secure.
Additionally, the type of potting material used can affect DC resistance as well. Wax has lower DC resistance than epoxy; plus it’s much easier to un-pot if your pickup requires rewinding down the line.