The P-90 pick up
This is one of my favorite pick ups for guitar after the Mosrite single coil. It has the clarity of the "Fender" single coil with the punch of the humbucker. Being a single coil design the tone of a P-90 is somewhat brighter and more transparent than a humbucker, though not quite as crisp and snappy as Fender's single coil pickups. The tone therefore shares some of the single coil twang, but having large amounts of midrange and often described as brisk. Popular guitars that use/have the option of using P-90s are the Gibson SG, Gibson Les Paul, and the Epiphone Casino. The pickups used in the Fender Jazzmaster are often confused with the P-90, however their only similarity is cosmetic since there are many significant visual, dimensional and electrical differences.
All vintage P-90 pickups are hand-wound, thus their physical specifications may vary slightly. In common with many other pickup types, there are two versions of P-90: neck and bridge version. Their DC resistance tends to be around 7-8 kΩ for neck pickups and 8-9 kΩ for bridge pickups. Earlier pickups (around 1952) used Alnico 3 magnets, but in 1957 Gibson switched to Alnico 5.
P-90 pickups were introduced in 1946 when Gibson resumed guitar production after World War II. They were originally used to replace the "bar" pickup (also known by many as the 'Charlie Christian pickup) on models such as the ES-150, and by the end of the 1940s it was the standard pickup on all models, including the Les Paul introduced in 1952.
The P-90's reign as the Gibson standard pickup was short-lived, however, as a new design of pickup known as the humbucker (occasionally named PAF) was introduced in 1957, and very quickly took over as the preferred choice for all Gibson models. The P-90 was then used on more budget models such as the ES-330, the Les Paul Junior and Special, and the SG Junior and Special, such as those used by Pete Townshend. This trend continued throughout the 1960s and particularly in the early 1970s where the pickup all but disappeared from the entire Gibson range. By the 1970s, single-coil pickups, mini-humbucking pickups and uncovered humbucking pickups began replacing the P-90 pickups on Gibson's budget and lower-end models.
In 1968, however, Gibson re-issued the original, single-cutaway Les Paul - one version of which was a Goldtop with P-90 pickups. In 1972, they produced Limited Edition reissues - the "58 Reissue" - actually based on the '54 Goldtop Les Paul, with a stopbar tailpiece; and the '54 Custom, the Black Beauty, equipped with a P-90 in the bridge and an Alnico 5 pickup at the neck - the total production of these guitars was quite small. In 1974, Gibson put the P-90 pickup in their Les Paul '55, a reissue of the Les Paul Special from that era. It was followed in 1976 by the Les Paul Special Double-cutaway model and in 1978 by the Les Paul Pro Deluxe. Since the 1970s the P-90 pickup has seen some success in various models in the Gibson line, mostly through reissues and custom versions of existing models.
One drawback of the P-90 pickup is its susceptibility to 50 Hz / 60 Hz cycle mains "hum" induced in its coil by external electro-magnetic fields originating in mains powered electrical appliances, motors, lighting ballasts and transformers etc. This susceptibility is common to all single-coil pickup designs, however the P-90 having around 2000 more turns of wire in its coil than Fender single coils produces a large amount of hum and for some players is objectionable enough to drive them to use side-by-side humbucking pickups instead. Several manufacturers now make hum-canceling pickups that share the form-factor of a P-90 and claim to have a similar sound. Obviously the arrangement of coils and magnets is different to the standard P-90, so the sound can never be an exact replica of the original.