Guitar pickups are transducers. Their function is converting string vibrations into electric signal. The two most common types of pickups are Magnetic and Piezo. This article will give you a basic idea of how pickups work and what kinds of sounds are produced by different types of pickups.

Piezo

Piezo pickups are used mostly on acoustic or semi-acoustic instruments, like the classical guitar where the nylon string vibrations cannot be captured by a magnetic pickup. Piezo pickups usually use ceramic crystals to convert the mechanical vibrations into electric signal and often have a better frequency response compared to magnetic pickups. They also have the advantage of not capturing undesirable magnetic noises. Piezo pickups are often hi-impedance and are therefore combined with pre-amps/buffers mounted on the guitar. The pre-amp corrects the impedance and offers additional tone shaping using the EQ.

Magnetic pickups

The most commonly used pickup in the guitar world is the magnetic pickup. Magnetic pickups consist of one or more magnets wrapped with copper (or other types of metal) wire. Guitar string vibrations alter the magnetic field of the pickup, inducing variable electricity.

By changing a few variables, the pickup response can be altered in order to achieve different timbre variations.

Using strong magnets will result in higher voltage output.

The number of wire windings also affects the pickup response. More windings will result in higher output volume and the increase of mid frequencies, but this will also result in the loss of high frequencies. There are two types of magnetic pickups, Ceramic or Alnico, each with his own sound characteristics.

From the construction point of view, there are also 2 variations of magnetic pickups: single-coil and Humbucker.

Single-coil

A Fender type single-coil is the simplest type of magnetic pickup.

The pickup is formed by 6 magnets, each one aligned with a single guitar string, all wrapped with a single copper wire. There are also pickups with a single magnet that cover all the guitar strings. The main characteristic of the single-coil pickup is its typical clean and crystal sound. The main problem, on the other hand, is the hum and background noise.

Single coil pickup

Humbucker

The humbucker, patented in the 50’s by Gibson, derives its’ name from the need for reduced noise from guitar pickups.

A humbucker is a double coil pickup; it's like having two single-coil pickups wired in series, with opposite polarities and windings.

The benefit of this type of wiring is the significant reduction in hum and noise. Compared to single-coils, humbuckers have higher output and a darker sound.

The coils inside the humbucker can also be wired in parallel (very rare). This type of wiring produces a lower output and a brighter sound compared to the same pickup wired in series. The difference between the so called “Bridge Pickup” and “Neck Pickup” is in their output level.

The Bridge Pickup will generate a lower output compared to the Neck Pickup due to the fact that the strings vibrate more in the neck position, so the Bridge Pickups will have a stronger output compared to the same Neck Pickup in order to balance the outputs.

Humbucker

Active pickups

Untill now we’ve talked about passive pickups. These pickups use a magnet and an electromagnetic field to generate electrical current.

Active pickups on the other hand require an electrical source to operate (usually one 9 volt battery). These pickups use less windings around the magnet, resulting in lower impedance, lower output level and an overall cleaner and quieter sound. The active pickup is combined with pre-amps which amplify the signal and offers more tone shaping. Active pickups can be either single-coils or humbuckers.

Active and passive pickups can be combined in the same guitar but this rarely a solution due to the fact that these pickups need different components (potentiometers, condensers) to operate making the wiring complicated. Active pickups are very popular among Rock/Metal players.

Adjustment

In order to get the best from your pickup, the height must be set correctly.

The height of the pickup is adjusted by raising or lowering the entire pickup or each coil separately, depending on the pickup model.

Lower strings vibrate more than higher strings, so the pickup must be set closer to the higher string to compensate the different output generated.

If the pickup is too close to the string it will exercise a stronger attraction to the strings, resulting in containing the string vibrations and reducing the sustain.

If the pickup is too far from the string, this will result in lower output and a cleaner sound.

Wiring

There are different possible types of pickup wirings. Usually, single-coil pickups are wired with 250K Ohm potentiometers for volume and tone while humbuckers usually use 500K Ohm pots.

The term series/parallel also refers to the way the pickups are wired to the pickup selector, parallel being the most commonly used.

The same series/parallel consideration made for wirings inside the humbucker can be applied for wirings between different pickups.

Two pickups wired in series will result in a stronger output level compared to the parallel wiring for the same pickup (note the volume drop in the 2 and 4 positions on the Stratocaster, or Ibanez type guitar, where the neck-mid and mid-bridge pickups are wired in parallel).

If the wiring of two pickups generate a weak output, it is possible that the two pickups are wired out of phase. In this case, invert the (-) and (+) of one of the pickups to correct the phase.