Burns Tri-Sonic
# Burns Tri-Sonic

The Burns Tri-Sonic is a single-coil electric guitar pickup, with ceramic isotropic ferrite magnets and a chrome cover. This pickup is significantly different to most other pickup designs. Tri-Sonics are wider than the more popular single-coiled pickups, such as used by Fender, so if Fender pickups are replaced with Tri-Sonics physical changes to the guitar may be required, such as routing the body or altering the mounting mechanism.

## History

The history of these Burns Tri-Sonic begins in England in the 1950s, the primary assembly site. The coils and backplates were produced in West Germany. When Jim Burns got into business with Henry Weill, in those years the pickups were much bigger, almost looked like P90s. Together they started a small production of solid body electric guitars on which they mounted these pickups. In 1960 Burns decided to go on his own way and the collaboration with Weill ended so the pickups became smaller size. For complete story, please go here: https://www.theredspecial.com/2019/01/tri-sonic-history-by-adrian-turner/

## Two type of Tri-Sonic

There are two different types of Tri-Sonic but only one of these has become famous, partly thanks to the success of Brian May with Queen and his Red Special. The less famous model is the one that mounts six cylindrical magnets riveted on the backplate, the coil is placed between the magnets and side flanges of the backplate. The cylindrical magnets remain exposed through the holes in the pickup top case. After some time, to save on production time, Burns decided to replace the cylindrical magnets with a single bar or two alnico bars hidden by a plastic mold glued under and inside the cover. Very often were used the magnets available in the laboratory so they produced Tri-Sonic made of Alnico magnets rather than isotropic ferrite magnets, sometimes they could be installed six square blocks of Alnico magnets, then it was decided to standardize the production to two isotropic ferrite bars: these are the pickups that Brian May bought at the Burns shop in 1963 to install them on his self-made Red Special guitar.

## Construction

The construction of the Tri-Sonic happens in layers. The backplate acts as a support structure for the whole pickup, the magnets are inserted above and in the center and the coil is placed between the side flanges of the backplate and the magnets, the chromed brass cover covers the whole structure. The name "Tri-Sonic" is given by the fact that the backplate is magnetized and extends the magnetic field in a larger portion of the guitar strings.

## Backplate

The backplate is made of steel and is magnetized upon contact with the magnets, its side flanges contain the coil and extend the magnetic field creating a totally unique sound, different from all other types of pickups.

## Magnets

The magnets of Tri-Sonic are made of isotropic ferrite. In the production process, isotropic ferrite is magnetized only after it has cooled down, this does not allow the orientation of all the magnetic crystals, generating a weaker oriented magnetic field than anisotropic ferrite. With backplate magnetization, all inductance is boosted up. With a non-magnetizable backplate, the inductance would drop down dramatically. The magnets are magnetized axially, in the Tri-Sonic the two ferrite bars are glued together with the same poles facing the same side, this allows them to become a single magnetic bar that sits perfectly along the backplate. The strings are read from the single pole. Unfortunately these magnets went out of production in the early 70's.

## The coil

The coil is made of 44awg (american wire gauge). In early production years they used a wire with brownish enamelled copper wire but, due to easily wire breaks, the coils were wound with an orange enamelled copper wire (formvar). In modern Tri-Sonics a plastic support is used to wind the coil on (bobin-wound), in vintage Tri-Sonics the coil was wound on a cardboard through a temporary support which was removed when the coil was completed (air-coil). A cloth tape closes and protects the coil so it can be placed on the backplate between its side flanges and the magnets in the center. The 44awg wire allows to reach good levels of DC resistance with a low number of turns (about 5350), this keeps the inductance low with a classic single coil DC resistance, in fact these pickups have a weak output volume (low inductance with normal DC resistance).

## Chromed Brass Cover

A cover is attached which fits over magnetic flanges running either side of the base. There are six holes in the pickup cover, through which can be seen a piece of black plastic which is glued to the inside. The six holes are only for aesthetic and design, not having any kind of function. In the first version of Tri-Sonic with six cylindrical magnets, there is no black plastic under the chromed brass cover. The cover is welded with the backplate to close the whole structure. To reduce radio interferences, a ground black wire is soldered to cover and backplate which is then soldered to the guitar ground.

## Brian May Red Special's neck pickup

In 1963 Brian May had almost finished building his guitar with his father, the guitar was really completed in 1964. Due to space constraints, Brian was unable to install the neck pickup so he decided to open it and remove the backplate, cutting the mounting brackets from the backplate. After giving a casting of epoxy glue (Araldite) in Tri-Sonic cover with inside magnets and coil, he stuck the mounting brackets in the glue. When the glue dried Brian reinstalled the modified neck Tri-Sonic in his Red Special, the space problems were solved. Having removed the magnetically backplate, the inductance of the pickup dropped down to 1.6Henry and changed the way pickup captures strings vibrations. When middle pickup is activated with modified neck pickup out of phase, a screaming soft sound is obtained, Brian later used that magical sound to record the famous center guitar solo of Queen song Bohemian Rhapsody (1975).

## Other versions of Tri-Sonic pickup

Burns Mini Tri-Sonic: designed to fit directly into Fender style pick-guards, these pickups are made with bobbin-wound, anisotropic ferrite single magnet and not ferromagnetic nickel backplate.

Burns Vintage Tri-Sonic: bobbin-wound coil, anisotropic ferrite single magnet and not ferromagnetic nickel backplate.

BooHeung Precision Machinery (South Korea): bobbin-wound coil, anisotropic ferrite single magnet and not ferromagnetic nickel backplate (mounted on Standard BMG Red Special).

DiMarzio BHM (out of production): designed to fit directly into Fender style pick-guards, made of bobin-wound coil, anisotropic ferrite single magnet and not magnetically nickel backplate, plastic cover and bottom (mounted on Guild Red Special Replica).

Kent Armstrong: bobbin-wound, anisotropic ferrite single magnet and magnetically steel backplate.

Burns Brian May Signature Tri-Sonic: made with air-coil, isotropic ferrite magnets and magnetically steel backplate.

Adeson: air-coil, isotropic ferrite magnets and ferromagnetic steel backplate (mounted on BMG Red Special Super).

* Comparison of the sizes of a Burns Tri-Sonic Brian May pickup (Bottom) and a standard Stratocaster style pickup (Top)
