Passive pickups used for guitar and bass is in general a musical instrument pickup consisting of a permanent magnet material such as Alnico, Ceramic or other specified material such as Rare Earth. A coil form or bobbin of a certain length, width and height needed to hold the wound coil. Magnet wire can be wound directly around a magnet such as the Dan Electro “Lipstick” tube pickups. Magnet wire can be wound around rod or blade magnets, studs or blades of soft iron or special grades of magnetically conductive stainless steel. Various gauges of magnet wire are wound to a desired number of turns and layers. The desired number of turns per layer are done with a coil machine with an automatic traverse control. Scatter winding hand layers the turns to the winders specific needs. Passive pickups have many wiring and phasing options. Passive pickups use no internal or external pre-amps.
Active pickups consist of a magnet source and material, a coil wound for desired impedance and frequency and pre-amp or booster usually built internally or externally and consisting of a battery or power supply. Active pickups can use various forms of power such as 9 volt, 18 volt etc., similar to condenser microphones that use a 48 volt phantom power supply either by internal batteries, a connecting box or power from the sound board. Active guitar and bass pickups usually have a fixed magnetic polarity facing the strings, fixed internal electrical phasing and lower impedance coils. Most active pickups are potted in a resin that eliminates tampering and repairability if the pickup fails. Both passive and active pickups can have external active tone circuits and pre-amps added but caution must be taken with adding new circuits with existing power supplies.