Rewinding, Building and Restoration of Pickups

My exploration in winding pickups: Initially it was just a curiosity in recreating 1958/9 Strat pickups with materials and methods from that period. Encouraged by how well these sounded, several other types of vintage pickups were made. These included the P90 and Classic Humbuckers.

I also offer services for restoring some types of vintage, non-functioning pickups. Please contact me for details. Perhaps I can help.

A few examples of my work.

Pre-CBS spec, Strat-style Replicas

Vintage Spec P90 Replicas.

Various Vintage-spec Humbuckers. The bridge is a classic recipe while the neck pickup shown here is experimental --- using both rods and blade cores.

PAF-style vintage-specification Humbucker.

A Few Custom Pickups:

Seymour Duncan, STK-series Replicas (Bridge shown above, complete set shown below)

Humbucker-sized Sidewinder. A dual-coil, noise canceling design.

Stacked Single-coil noise canceling design.

Low-impedance, wide-range pickup in Humbucker format.

DeArmond-Rowe 1950’s Pickup Replica

These are my efforts to recreate the sound of my first electric guitar; a 50/60's era "Carlton". At the time, those "guitar mikes" were like magic. I never even dared taking the cover off to look at the inside. Good thing too because that probably would have ruined the delicate insides.

Research indicated that Harry DeArmond invented the first commercially-available, detachable guitar pickup in the 1930s and with Horace 'Bud' Rowe's company, they manufactured hundreds of them. By 1975 they had manufactured over 100 different kinds of guitar pickups. Many of these early pickups shared a common theme; a permanent magnet over which a coil was wound. The coils often were wound directly over the bare magnet with no bobbin. Given the wire is only the thickness of a human hair, this was tricky business and creating a working pickup was really more of an art.

My replica is shown below inside a humbucker mounting ring. The actual pickup is 70mm long x 30mm wide x 15mm thick.

The insides of my replica.

The construction of the pickup is rather simple: a steel structure to hold magnets, a coil, some pole screws, and a protective plastic cover.

Note the magnets are actually the kind used in refrigerator art. They are 12mm diameter disks, about 5mm thick ceramics and there are five of them. Each measure about 850 Gauss. The coil has a DC resistance of about 8K Ohm and an inductance of 2.2 Henries.

Besides being a single coil, the magnetic field are spread out further along the string instead of being focused like a rod-based design. You can see how that is achieved with the pole screws being part of the magnetic structure. With these magnets, the pole screws has the opposite magnetic polarity than the top of the magnets ... on mine, the poles read about 130 Gauss North up, whilst the magnets read about 800 Gauss South Up.

Making the coil is rather tricky. Since there is no bobbin, one need to somehow contain the wire wraps whilst on the winding spindle. I have made a special jig, a kind of dummy bobbin that tightly sandwiches the magnets between two plates. These coils are wound with #45 poly. The wire is freakishly thin thus tension needs to be carefully controlled.

One need to somehow wrap the entire coil at several places to form a stable bundle before it comes out of the jig, else those wires seem to just have a will of their own and the whole thing falls apart. I pre-install a couple of pieces of electrical tape strips inside the jig before winding, then when done, these tape flaps are folded back to enclose the loose wire loops. The whole coil is then lengthwise wrapped with tape. I also wax pot the coil assembly.

The base is actually a piece of 1" x 1" galvanized angle iron. It is cut to size, then one side is cut down to the required height and a row of holes drilled along the open side. These holes are threaded to take regular 5-40 Fillister-head screws like those used on humbuckers.

For the sound connoisseur: Some sound clips recorded with my AC15 clone amp using the top-boost channel with modest cut control setting. The sound was recorded with a SM58 mike set up some 6" from the speaker.

The recordings were made with a two-pickup version installed on my "Plywood Special" test guitar at the neck & bridge positions.

1. Barebones-tone with the guitar plugged directly into amp. No effects. Cycling through Neck-Both-Bridge pickup selections.

http://www.johanforrer.net/Guitars/PickupBuilding/Carlton/BareboneTones.mp3

The following recorded with added Quad GT with EFTP effects.

2. Neck pickup.

http://www.johanforrer.net/Guitars/PickupBuilding/Carlton/Sleepwalk-Carlton-Neck.mp3

3. Bridge pickup with slightly more on treble cut.

http://www.johanforrer.net/Guitars/PickupBuilding/Carlton/WonderfulLand-Carlton-Bridge.mp3

The “Slim Jim” Slim HumBucking Pickup

It is always a challenge to accommodate pickups on guitars with tight clearances between the strings and guitar body. Either some kind of routing is needed or very slim pickups are required. In many cases, like for example, valuable archtops, routing is out of the question and some form of slim sensor profile is required.

Several kinds of transducer might work, like for example, under-the-bridge piezo transducers, or other body-vibration sensors. A low-impedance, current-sensing transducer, like the Alumitone may perhaps be shaped into a flat profile and used with remote electronics. Another possibility is to employ miniaturized technology similar to the hexaphonic pickup, such for example, the Roland GK-2A as used for guitar synths.

A conventional electro-magnetic approach is followed here to explore manufacturing possibilities as well as evaluating the sound character of such a slim-line pickup. Since the objective was to reduce the height of the pickup, the name “Slim Jim” was thought appropriate.

The Slim Jim prototype:

Two side-by-side coils configured in humbucking mode. The coils are slightly offset to span all the strings. The arrangement is similar to a Fender P-Bass pickup.

The sensor uses ceramic bar magnets, 5mm thick and 45mm long. These were chosen for their strength and size. Magnetic strength measure about 820 Gauss --- to be used in humbucking mode, one set are configured South-side up and the other North-side up.

The magnets are sandwich between two flat flanges that forms a crude bobbin to hold the coil. To further reduce the pickup height, the magnets are glued with epoxy into small slots in the bottom flange such that the bottom edge of the magnet is flush with the bottom flange. The prototype uses thin acrylic glued to the top of the magnet for the top flange, however, it would be possible to use some kind of jig to form the coil without the top flange. The height of the pickup would be about 4.76mm (3/16”) if manufactured like that.

Slim Jim bobbins prior to winding.

The prototype was wound according to typical humbucker specifications: 5000 turns enamel wire. 44 AWG SPN was used which filled the coil space without spilling over. To protect the integrity of the delicate coil, the assembly was potted in wax.

A four-wire hookup allows for using the pickup in split mode, single-coil or humbucking operation.

A sound sample was produced and given below where the Slim Jim pickup is contrasted with a conventional hand-wound humbucking pickup installed in a test guitar.

1. For hum evaluation purposes, the pickups are held about 12” directly in front of a CRT: First part, the conventional humbucking pickup. Second part, the Slim Jim.

http://www.johanforrer.net/Guitars/PickupBuilding/SlimJim/SlimJimHum.mp3

2. Bare tone contrast: First part, the conventional humbucking pickup. Second part, the Slim Jim.

http://www.johanforrer.net/Guitars/PickupBuilding/SlimJim/SlimJimTone.mp3

3. Played with a backing track; my version of Peace Pipe. A DI recording using the Slim Jim fitted to the Plywood Special as shown above.

http://www.johanforrer.net/Guitars/PickupBuilding/SlimJim/PeacePipe.mp3

How a Custom Pickup is Made --- Example of an Overwound Bridge Single-Coil

Step 1: Parts procurement. Forbon top and bottom plates, cut and drilled. Magnets.

Step 2: Bobbin assembly. Magnets are pressed in and glued in place. The assembled bobbin is then dipped in lacquer. Magnets are taped to prevent coil shorts and damage to the coil due to possible oxidation (by sweaty hands and perspiration). Brass eyelets for lead wire connections are installed.

Step3: Winding the coil. Using a computer-controlled winder, several thousand wraps of fine wire are wound on the bobbin. The windings laid down for this pickup is in a random-scattered pattern, similar to a hand-guided process.

Step 4: Charging the Magnets. Magnets used for this project are uncharged otherwise all sorts of unwanted iron filings would be attracted and cause all sorts of problems. The magnets are charged after completion of the coil winding. A pair of strong neodymium magnets mounted in a small vice does the magnetizing.

Step 5: Verification. The magnetic strength and polarity of each magnet is checked with a magnetometer. This assures that all magnets are charged to their desired strength and quality. This gives assurance that there are no duds, i.e., show abnormal low or high strengths (maybe a bad magnet or one of the wrong type).

Step 6: Packaging. In some cases the pickup is dipped in hot wax (mixture of paraffin wax and beeswax) to seal out moisture and limit microphonics. Unless specifically required, I do not wax pot my pickups. The completed pickup is placed inside a cover, ready for installation.