Almost all pickups found on electric guitars are based on electromagnetic induction, which means creating an electrical current by using a changing magnetic field and a coil of copper wire.
In contrast to a dynamo or a power generator, both the magnet and the coil are stationary in a guitar pickup. Here the guitar string’s vibrations ”mix up” the magnetic field and cause a current to flow.
The resulting weak electrical signal passes through the guitar’s controls and – via the lead – on to the guitar amplifier, where the signal is amplified, so it can drive a speaker.
While virtually all pickups follow the same basic principles they are generally divided up into four types according to their different build:
* singlecoil pickups
* humbucking pickups
* active pickups
The singlecoil pickup
The singlecoil pickup is the oldest and most basic pickup type of all. The most common singlecoils are the ones used in Fender Telecaster and Stratocaster -guitars, where six slug magnets are stuck into two plates made from vulcanised fibre. The coil is then wound around the magnets.
These slim and tall pickups tend to have a bright, cutting sound.
Check out these examples:
The P-90 is the oldest Gibson-pickup still in regular use. Even though the P-90 is also a singlecoil pickup, it is put into its own category due to its different build.
Here the coil is wound around a plastic coil former with two oblong magnets stuck on underneath. The coil is much flatter and wider than a Fender-style singlecoil.
A wider coil isn’t able to pick up high frequencies (treble) as well as a narrow one, which is why a P-90 generally has a more middly tone than a Fender-singlecoil:
The P-90 is build in two main versions. For installation on semi-solid guitars a bottom-plate with installation brackets is used in combination with the so-called dog ear -cover. On solidbody guitars the P-90 is mostly installed with two long screws through the top of the unit, and a smaller ”soap bar” cover is used.
Singlecoil pickups sound great, but they all have one problem in common – they pick up noise from transformers, fluorescent lights, computer monitors, DVD-players etc, because a copper coil always acts as an antenna.
In the mid-1950 engineers started to develop ideas for noise-free guitar pickups. These days the anoraks like to debate who came first – Ray Butts, who invented the Filtertron-pickup for Gretsch, or Gibson’s Seth Lover.
In any case, in the end Gibson’s unit became the de facto industry standard.
The Gibson-type has two coils arranged next to each other, with a single oblong magnet stuck underneath, between the coils and the pickup’s bottom plate. Because the coils are wound in opposite directions, but their magnetic polarity is different, the noise is cancelled out while the guitar string’s vibration is picked up.
The original pickups were built with metal covers, but in the mid-Sixties some Blues-players (for example Eric Clapton) discovered you could squeeze out a few more drops of treble once the cover is removed (don’t try this at home, you can easily ruin the pickup).
Thanks to its twin coils a humbucker generally sounds bigger and fatter than a singlecoil, which is great for achieving overdriven and distorted tones.
This is what a typical humbucker sounds like:
The active pickup
The main difference between an active pickup and the three other pickup types is that the active pickup is equipped with a built-in pre-amplifier. Most active pickups are humbucking and come either in the Gibson-humbucker size or shrunk to fit a Stratocaster-pickup’s dimensions.
Thanks to their preamps most active pickups have a healthy output signal with a very clean tone. Most active units’ guts are sealed with plastic resin inside their cover, making them practically immune to feedback (a loud, howling or whistling sound from the amp) even at very high volume levels. This is why active pickups are very popular in the Metal genre.
The only drawback is that your guitar won’t work without a 9 V -battery.
This is what an EMG 81 sounds like:
Why do most electric guitars have more than one pickup?
The position of a pickup on a guitar influences what the pickup ”hears”.
The closer the unit is moved towards the bridge, the brighter and sharper the sound gets. The closer you move to the end of the fretboard, the warmer and fuller the sound becomes.
If a guitar is equipped with with more than one pickup you can use a switch to quickly select the desired guitar sound – either by selecting a pickup on its own or by combining two (or even three) units.
Here I’m switching from the neck pickup to the bridge pickup and back again: