Now that we’ve established the difference between active and passive pickups, let’s look at different types of pickups that can fall into either the active or passive category.
Pickups consist of a magnet around which a copper wire is coiled. When the vibrations of a bass string disturb the magnetic field of the magnet, small voltage fluctuations in the copper coil are produced. These fluctuations are then transmitted to the bass amp, amplified and translated into sound.
There are two prominent pickup designs based on the number of coils used in a pickup’s construction single-coil and double-coil.
Single-coil pickups have one coil wrapped around the pickup’s magnet. Single-coil pickups are often bright and clear sounding. A drawback is they can pickup external noise and give off a humming sound. Radio waves, computer monitors, and florescent lighting can all cause this humming/buzzing. If two single-coil pickups are used (as on a Fender Jazz bass) and the pickup volumes are set equally, the noise will get cancelled out. If you just use one of the pickups, you may pickup some noise.
Double-Coil - Humbuckers
Just as two single-coil pickups can be put together to cancel hum, a double-coil pickup can be created to cancel the hum within one pickup. These pickups are often called humbuckers or humbucking pickups for their hum-reducing qualities.
Humbuckers tend to roll off some of the tonal highs when they cancel the hum and they usually have more output than single-coils.
Split-coil pickups are basically double coil pickups split apart. This is what you see on Fender Precision basses. Instead of one double-coil underneath all 4 strings, the pickups are split in two each under one pair of strings.
Piezo pickups are less common on electric basses, but you may run into them. A piezo pickup senses the actual vibration of the string through contact with the string at the bridge contact point. These are often found in acoustic bass guitars. Since piezos don’t rely on magnets it is possible to use non-metal strings such as nylon strings. Piezos, without the right kind of pre-amp, can sound brittle and thin.
The newest kind of pickup available is the optical pickup. Optical pickups use light to sense the vibrations of the strings instead of magnets. These are still very uncommon, but may catch on.
Other Pickup Terminology:
Soapbar pickups refers to the shape of the pickup housing. They look like bars of black soap. Often found on 5- and 6-string bass guitars.
An MM-style pickup refers to pickups created by and used on MusicMan basses.
Next: Bass Pickup Placement
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