Gibson Guitar Corp. designed the first humbucker electric guitar pickups, and they're installed on their Les Paul and SG models. Most Fender Stratocasters and Telecasters use single-coil pickups, but there are some styles, like the Fat Strat, that incorporate humbuckers. Seymour Duncan and EMG are also known for their humbuckers. These two companies are concerned with pickups and effects exclusively and don't sell guitars. EMG has developed a solid reputation among fans of heavy music like metal. Seymour Duncan pickups have a little more range.
Humbucker pickups often have a thin metal plating covering the magnets. The difference is that the magnets of the pickup are not directly exposed. Pickups without covers are known as open coil pickups. Many people cannot tell the difference between the two in sound. Though some say open coils are a bit brighter and covered pickups handle distortion better, it primarily comes down to personal choice.
The core of any pickup is the magnet that detects the guitar strings' vibrations. Magnets can be seen In an open coil pickup as these are little metal dots that form a line down the pickup. There's usually about six per coil. There are a few different types of magnets used in pickups and each has its strengths and weaknesses. The three most common are Alnico II, Alnico V and ceramics. Few players get a clean sound from ceramics. They are known for producing a good distorted sound and many prefer them to the Alnico types. Alnico II has the lowest output of the three types. It tends to sound warm with lots of bass. Alnico V has a higher output and has more treble and midrange sounds.
Most humbuckers have the two coils placed side by side, but sometimes they're placed in different configurations to affect the sound and look of the guitar. Stacked humbuckers have the two coils stacked on top of each other. This was originally done so that double coil pickups could easily fit in guitars built for a single coil pickup. However, some guitarists find their special sound is preferable to traditional humbuckers. Rail humbuckers have two coils side by side, but they are squeezed into the size of a single coil pickup. These produce a tremendous amount of gain.
The most common arrangement for humbucker pickups is to place one near the bridge and one near the neck. Some guitars, such as the Gibson Firebird X, add an extra pickup in the middle for more variation. One type of Stratocaster, called a Fat Strat, uses two single coil pickups and one humbucker located at the bridge.