Burns Tri-Sonic Pickups: General Information

Introduction

This article is intended to provide general information on Burns Tri-Sonic pickup variants for enthusiasts and guitarists who are interested in their deployment in Brian May Red Special guitars; no background technical knowledge is assumed. Guitar pickups are relatively straightforward passive devices (i.e. no do not contain any moving parts) consisting of a coil of wire and one or more permanent magnets enclosed in a casing. A small electrical current is induced in the coil when the steel strings of the electric guitar they are attached to cut magnetic field lines generated by the magnet(s). This current can be amplified and altered by effects to yield pleasing tones.

I have based this article on facts rather than uninformed conjecture arising from perceived mystique associated with a particular famous guitar player and referenced out to more authoritative sources where appropriate. The two images below are ‘library pictures’ of a single Kent Armstrong Tri-Sonic pickup (left) and a set of three Burns Brian May Signature Tri-Sonic pickups (right).

History

If you are interested in a detailed history of Burns Tri-Sonic pickups, I recommend that you read the text of an interview conducted by Simon Bradley in 2011 with Adrian Turner of Adeson Fenton Weill in Burbage, Wiltshire, U.K. who is the expert in the field of hand building and repairing these pickups. This was intended for publication in the official Red Special book but was subsequently omitted and instead published on the related website:

https://www.theredspecial.com/2019/01/tri-sonic-history-by-adrian-turner/

In the interview, Ade outlines why there was considerable variation in the component parts of pickups assembled in the 1960s which is relevant background information to understanding the characteristics of the specific pickups fitted to Brian May’s Red Special guitar. These pickups were named Tri-Sonic because they have a wide, triple zone pickup area. Barry Gibson who formed Burns London Ltd gives us some further insights: the reason for the name, is that the magnetic field emanates from three points: the top and both sides and so can interact with a longer-than-usual length of string. The result is a uniquely big, round sound although it is not known whether this was a design feature or an unintended benefit. The original U.S. patent (3,249,677) illustrated below was filed by James Ormston Burns et al. on 19 October 1962 and granted on 03 May 1966.

Theory

If you are interested in the theory of guitar pickups and other electronic circuits related to guitar effects and transistor and vacuum tube based guitar amplifiers, I highly recommend the book Electronics for Guitarists by Denton J. Dailey published in 2011 by Springer, ISBN 978-1-4419-9535-3, DOI 10.1007/978-1-4419-9536-0.

Physical Description

Burns Tri-Sonic pickups consist of two half bar magnets measuring 5/16″ × 5/16″ × 1 1/8″ with top faces north polarity and bottom faces south polarity with a single coil of around 5,100 to 5,200 turns of 44 AWG (American Wire Gauge) enamelled copper wire wrapped in tape and placed between the casing and the magnet. A piece of black plastic or rubber is usually placed on top of the magnet and the whole assembly mounted on a metal base plate and covered with a chromed brass case measuring 2 7/8″ to 3″ long, 7/8″ to 15/16″ wide and 13/32″ to 7/16″ high with six holes of 5/16″ diameter spaced at 3/8″ intervals. The holes are now a cosmetic feature and have no physical function but originally allowed for exposed magnets. The coil is wound on a removable chassis, completely wrapped in a special armature winding tape and then pulled tight. The magnets are vintage ferrite ceramic similar to Alnico 2 which has been out of production since the early 1970s.

The pictures in the gallery below are hidden line CAD renders I produced to illustrate the component parts of a ‘typical’ vintage style Tri-Sonic pickup described in the previous paragraph. I have simplified the coil assembly to show the general appearance of the wrapped whole winding.

The Sound of Tri-Sonic Pickups

The tonal characteristics of a typical Tri-Sonic pickup is between that of a standard single-coil pickup and a double-coil (humbucker). It has more warmth than standard single coil pickups, so feeds back a little easier, but it also has more treble response than a humbucker, and does not self-limit at high levels because its inductance (approximately 2.1 H) is lower. Brian May has always used a treble booster as the first effect in his signal chain because the raw tone of a Tri-Sonic is somewhat indistinct although this device also adds gain to the signal which helps overdrive the Vox AC30 amplifiers he uses.

Brian May Red Special Burns Tri-Sonic Pickups

Brian wrote a 1,000 word article entitled “O.k. I’ll tell the true story… the history of me and Burns Tri-Sonic Pickups…” for the original Burns London website which can be found at the link below:

http://www.burnsguitars.com/brianmaytrisonicpickups.php

Brian stated in the article that he bought his three Burns Tri-Sonic pickups for nine Guineas (21 shillings or £9.45) from the Burns showroom in St Giles Circus in London in 1963. Using an online inflation calculator, this equates to around £167 in 2020 which is approximately the cost of a set of three Brian May specification pickups from Adeson.co.uk. However, the neck pickup is physically different to the ones fitted in the middle and bridge positions and displays evidence of having been fitted with a paxolin base plate like the variants originally on a Burns Jazz guitar. This is partly why the electromagnetic characteristics (DC resistance and inductance) of Brian’s specific set are subtly different. The second reason is that in his search for controllable feedback and to reduce the microphonic nature of the Tri-Sonics, Brian subsequently modified the pickups in several ways:

Bridge Pickup
In an attempt to eliminate whistling, the original strip of 0.5 mm black plastic on the underside of the cover was changed for rubber. The coil was also covered with Araldite (a proprietary two-part epoxy resin) and the cover replaced so that all the constituent parts were immobilised as one solid whole.

Middle Pickup

The magnets were turned over and the positive and negative wires connected in the opposite polarity sense to the other two pickups so that it could act as a humbucking pair with another pickup selected in phase with it. There is some interesting discussion and speculation on enthusiast forums regarding whether the neck and bridge pickups were swapped and why, but this detail is not appropriate for a general interest article. Brian’s preferred pickup combination is bridge and middle in phase which he uses approximately 80% of the time.

Neck Pickup

The base plate was removed and the internal components covered with Araldite again immobilising the magnet, coil and cover as one unit to reduce the overall inductance of the casing.

Some unintentional misinformation was published in Guitar Player magazine in 1975 that Brian “re-wound the pickups”. In fact there is no evidence that Brian re-wound any of his pickups because the coils appear as he bought them; indeed it is inconceivable that anybody who had just paid a relatively large sum of money for a set of manufactured pickups to replace a set of home made ones would want to disassemble and modify them! It is likely that he either misspoke or was misquoted and simply meant that he “re-wired” them, i.e. reconfigured the wiring using the polarity posts on the Red Special.

Greg Fryer dismantled all three pickups during his 1998 restoration of Brian’s Red Special guitar. He photographed their component parts and subsequently published numerical values on his website which can be interpreted as indicative of each individual pickup’s DC resistance, inductance and magnetic field strength:

https://fryerguitars.wordpress.com/red-special-restoration-1998/

Tri-Sonic Pickup Variants

Over the years, a number of Tri-Sonic pickup variants have been commercially available including the sets hand made by Adrian Turner of Adeson Fenton Weill, Kent Armstrong versions and factory produced items made in South Korea by BooHeung Precision Machinery (BHK) to customer (e.g. Burns London or Brian May Guitars) specifications. As I have illustrated in this article, the principal differences between vintage style pickups and modern ones are coil configuration (i.e. bobbinless and taped or formed around a plastic piece and magnetic field strength. Ade offered some insights into the characteristics of vintage Tri-Sonic pickups on www.adeson.co.uk circa 2006 (edited for clarity):

The typical resistance of a 1960s vintage Tri-Sonic pickup is approximately 7.6 kΩ. This excludes earlier AlNiCo type Tri-Sonics which can measure over 8 kΩ. However, it is not unusual to find 1960/61 pickups with readings in excess of 10 kΩ. The overall sound of a 7.6 kΩ original type and a modern aftermarket 6.5 kΩ version are similar. The original types exhibit a smoother, “flutier” type of sustain – compared to pickups with modern magnets. However, output does seem to be remarkably similar. The unique sound of an original vintage Tri-Sonic pickup is primarily influenced by:

  1. Using vintage type lower field strength magnets is very important.
  2. The dimensions of the outer casing. This is important because the bottom plate reflects the magnetic field.
  3. The unique tape wound coil.

Modern type aftermarket Tri-Sonics built by various manufacturers from around 1990 to 2005 utilise higher field strength modern magnets, plastic bobbins and different depth casings. This is because they are set up to manufacture U.S. style bobbin pickups so the internal design of the original Tri-Sonic was adapted to allow production on modern machinery in a cost effective way. However, these pickups can sound sterile with an indistinct low end. To mitigate this, the number of windings was decreased which yields a thinner, more vintage tone.

Recommendations

Bearing all of the above information in mind, the two options I recommend at opposite ends of the price structure are the Adeson “original BM/Guyton” specification pickups for the discerning enthusiast seeking full authenticity for a high end Red Special replica and the unbranded ex-BHK factory versions offered by various eBay sellers. At the time of writing, I have six sets of Adeson Brian May specification Tri-Sonics: four installed in guitars and two available for future projects so I am well-placed to recommend them. My own measurements indicate that the unbranded BHK bridge pickup has a DC resistance of 7.1 kΩ and inductance of 1.8 H which should be sufficiently close to the Brian May specification neck pickup to be suitable for that purpose in a Red Special guitar variant. These unbranded Tri-Sonics can be bought for a very reasonable £20 each (£60 a set) making them a cost effective basis for modification and experimentation such as removal of the base plates and epoxy potting or loading your own home-made coils and/or magnets into.

Acknowledgements

I would like to thank specific members of the Brian May Red Special community including Mark Reynolds for many informal discussions on the topic and Julian Hemingway and Tim Grocott for sharing detailed information about their hobby pickup winding activities in forum discussions, all of which provided me with many new insights on Tri-Sonic pickups.