An electric guitar works through a device called a “pickup”, which is a transducer that translates vibration into electricity and delivers signals to the amplifier. Pickups can be made with one, two, and, to a lesser extent, three coils, each one basically comprising the wiring wound to a set of magnets. Depending on the number of coils and how the coils are arranged, one ought to expect a different output.
How do single-coil guitar and bass pickups work? Single-coil pickups work as antennas that convert the vibrations from guitar strings into audio signals. They presumably deliver a more natural and unfiltered string sound that double-coils, capturing all possible frequencies. Unfortunately, this also includes noise.
In this article, we'll be discussing the following:
- What a pickup coil is
- What a single-coil pickup is
- Differences between single-coil and dual-coil
- Differences between single-coil and P90
- Differences with other technologies
What Is A Pickup Coil?
Single-coil pickups work by capturing all the electromagnetic frequencies emitted by surrounding objects, emphasizing those nearby with a certain level of magnetism (notably the metal strings). The way the coiling is designed significantly impacts how the pickup operates.
The coil is what connects the magnets to the rest of the circuitry. It rests below the bobbin of the pickup and is composed of copper wire that is wound to the magnets by several turns, numbering thousands. The copper wire is usually insulated by polyurethane, but alternatively also by heavy formvar or plain enamel (particularly the older builds).
As the strings vibrate, they cause a changing magnetic field within the vicinity of the pickup's magnet. This change causes an electric signal (audio signal) to be induced in the conductive coil due to electromagnetic induction.
The wires are attached by machine or by hand, and they are responsible for inducing a small amount of electrical voltage as a reaction to a magnetic field set in motion.
The higher the number of turns around a magnet, the higher the gain around the midrange frequencies. Too many turns will result in a booming, dark sound with no distinguishing features. Conversely, an underwound pickup will not provide enough signal, and the sound will turn too thin and tinny.
We can identify the number of coils by the number of magnet rows visible in uncovered pickups. Contrary to what many people would think, the number of coils is not nearly as important as how they are assembled and connected.
Traditionally, electric guitars came with only one coil. The tonality was sharp, poignant and “twangy”. The Hawaiian wave in California during the 1940s made these instruments very popular ever since the first electric guitar (the Rickenbacker “Frying Pan” lap steel) came to the fore.
The single-coil pickups used at that time were very innovative, but they produced a 60 Hz hum that came from interference by surrounding appliances, lightbulbs, and circuits.
To solve this, Leo Fender included a middle pickup on his famous Stratocaster (first built in 1954) that was wound in the opposite direction to the others. By switching to positions 2 and 4, the hum would theoretically be cancelled out.
To learn more about pickup switches, check out my article How Do Guitar Pickup Switches Work & How To Use Them.
Later, the humbucker that would be featured on many Gibson and Ibanez guitars was designed to further tackle the humming issue (more on that later). Needless to say, some of the most famous electric guitar models in history, like the aforementioned Fender Stratocaster, to this day sport single-coil pickups.
How Single-Coil Pickups Work
Just as with the other magnetic pickups, they work through electromagnetic induction. When a string is played, the disturbance in the magnetic field is picked up by the magnets, and the coil reacts by converting that disturbance into electricity.
The electric signals produced can be affected by the quality of the magnets, the gauge/length of the wire present in the coil, and the number of windings.
The single-coil pickup is made up of three main components and a fourth optional:
The magnet is a piece of metal with a relatively high level of magnetism, from which the magnetic field “flows” or is projected.
The magnets can be made of AlNiCo, ceramic, and, more rarely, neodymium. These magnets have different performance traits, supplied by the material's hardness and atomic structure.
For more information on the different magnet types in guitar pickups, check out my article Ceramic Guitar Pickups Vs. Alnico Guitar Pickups.
To rephrase, the coil is composed of copper wire, varying in length and gauge. The coil is electrically conductive in order to have an audio signal induced across it properly.
Also referred to as the casing or housing under which the connections lie. The purpose of the bobbin is to protect the coil from damage due to accidental bumps or weather conditions, owing to the brittle nature of the wires therein. It also embeds the magnet poles and the slabs or plates.
The most common bobbin design includes two small plates at the top and bottom of the pole pieces, made from vulcanized material or glass-filled nylon. The bobbin is then inserted into the guitar body, sometimes with the help of a pickguard.
In addition to all of the above ingredients, active pickups carry preamps powered by 9V batteries. These are supposed to boost the gain of single-coil pickups while suppressing noise. Most guitars sold by manufacturers and retailers carry passive pickups, which could be replaced by active pickups if the owner desires.
To learn more about active pickups and pickup upgrades/replacements, check out the following My New Microphone articles:
• Upgrading Guitar Or Bass Pickups: Is It Worth It?
• Are Active Guitar Pickups Or Passive Guitar Pickups Better?
• Can Guitar Pickups Be Changed Without Removing Strings?
Differences Between Single-Coil & Dual-Coil Pickups
In contrast to single-coil pickups, dual-coil pickups offer a warmer and fuller sound with little noise. This pickup is composed of two sets of magnets wrapped in reverse polarity from each other, a design that allows for 60 Hz hum cancellation (hence the term “humbucker”).
By the mid-50s, Gibson issued the first guitars sporting humbuckers. The dual-coil arrangement was set to replace the traditional single-coil pickups that were prominent at that point, amending the hum problem that even the P90s could not successfully address.
Still, there was a caveat: the lack of brightness. On the one hand, the notes sounded much cleaner, but, on the other hand, they were not exactly fit for use in western swing music.
Additionally, rock musicians in the past also craved the “twangy” notes produced by single-coils, especially since the amplifiers of those days performed poorly at the higher frequencies.
Leo Fender introduced the angled pickup with the introduction of the Broadcaster (later “Telecaster”) model precisely in order to increase the high-end response of old amplifiers. The underlying principle behind this approach was that, at the bridge, the strings provided a brighter sound. Thus, the bridge pickup was installed in a slanted position, with the lower end towards the higher notes. However, this issue became irrelevant once Jim Marshall developed the 100-watt guitar amplifier in the mid-to-late sixties.
Humbuckers were, nonetheless, still targeted towards guitarists that sought a more controlled and “mature” tone (such as jazz or jazz-rock musicians) or those who fancied the darker distortion they provided at the low notes (fitting for modern metal).
To learn more about pickups and tone, check out my article How Do Different Types Of Guitar/Bass Pickups Affect Tone?
Differences Between Single-Coil & P90 Pickups
P90s were devised towards the end of the 1940s as a way to endow the sound typically heard from single-coils with a more wholesome timbre.
They also use a single magnet, albeit inserted in a wider and shorter bobbin. They have a higher output than single-coils, with a boosted midrange. They're often seen as a midway between single-coils and humbuckers.
For more info on “high output” and P90 pickups, check out the following My New Microphone articles:
• What Would Be Considered A High-Output Guitar/Bass Pickup?
• What Are P90 Pickups & How Do They Work?
Some may consider P90s a downgraded humbucker, but that is not necessarily accurate. A P90 has an established market among those guitarists who want to have the warm sound of dual coils but with a bit more “twang”. Some may find the versatility of P90s welcoming, as it allows session guitarists to perform in a variety of genres that the other two pickup types won't be able to due to their peculiar sonic characteristics.
Notwithstanding, Gibson guitars with P90s are deemed budget versions of the humbucking flagships, catering to jazz, blues, and hard rock guitarists with a lighter wallet.
Differences Between Single-Coil Pickups & Other Pickup Types
Let's compare single-coil pickups to the non-magnetic pickup types, notably piezoelectric and optical pickups.
Piezoelectric pickups are not magnetic like single-coil pickups (or any other type of magnetic pickup, for that matter). They work by means of mechanical stress, and the sound is rendered through crystals that, when pressed, generate an electrical current that is then transformed into audio signals.
The main difference between a piezoelectric pickup and a magnetic pickup lies in the type of sound. The single-coil magnetic pickup highlights vibrations from the metal strings and other interfering electrical appliances. Conversely, the piezo pickup catches the string's vibration and the vibration of other components such as the wood and the saddle. This gives the piezo a more close-to-acoustic sound in comparison.
Piezo pickups can be added to electric guitars with magnetic pickups to produce hybrid guitars. By working with both technologies, a wider variety of timbres can be squeezed out of them.
Optical pickups have a similar design to magnetic pickups, but they work with infrared sensors instead of magnets. This translates into virtually no interferences, a stark contrast to the heavy interference that single-coil pickups receive.
A downside of optical pickups is that they're very sensitive to high temperatures, a problem that magnetic pickups simply do not have.