A DIY Stacked Noise-Canceling Guitar Pickup

 

Through experiments with various kinds of guitar pickups, I’ve arrived at one particular pickup that fancies my taste. Not only does it sound great, but also is a great performer from a technical point of view.

 

I make no claims for originality of the ideas portrayed here. My own version is an extension of ideas gleened from similar noise-canceling, single-coil pickups manufactured by DiMarzio, Seymour Duncan, Kinman and others, also covered by several US Patents.

Summary of features:

  1. Single-coil sound,
  2. Electrical output level comparable to a Humbucking pickup,
  3.  Noise-canceling performance comparable to a Humbucking pickup,
  4. Can be used in sets, or individually; for instance, as a bridge pickup together with standard single coil pickups.

Topology:

As mentioned above, this is a stacked configuration. Imagine a regular Humbucker pickup with two side-by-side coils --- instead these two coils are stacked vertically. There are several benefits for this arrangement instead of the side-by-side configuration: cost savings in the reduction in parts count, reduced complexity in assembly, and retention of basic single-coil sound character.

 


A picture showing an empty pair of stacked bobbins of a prototype.

 

 

The assembled pickup is similar in size than a regular single-coil pickup, fitting the same pick guard mounting holes. However, due to longer magnets, it is marginally taller than the conventional single coil pickup and may require deeper routing.

 

Vintage magnet-height stagger or flat/even magnet stagger is possible. The magnets are Alnico V rods, approximately 5mm in diameter, 25.4mm long. Magnets shown in the picture are vintage staggered and have beveled top edges.

 

A prototype with completed windings.

 

 

This prototype was constructed using regular plastic Humbucker bobbins mounted on a Forbon base. Note the staggered Alnico V magnet. Also visible between the two bobbins is a shield plate. The plate is drilled to allow the magnets to pass through.

 

The completed pickup.

 

 

 

 

 

This one was made especially for my good Aussie friend, Barry.

 

 

Note the pickup has fairly high DC resistance, not unlike an over wound Strat pickup. Ideally, it this pickup works best with a 500K-volume potentiometer, however a 250K-volume potentiometer is workable and will have slightly less brightness.

 

 Installed in the bridge position it is a little hotter than the typical Strat pickup. Tone-wise it sounds very much like a 1950’s vintage Strat pickup. In my opinion, perhaps a little less brittle, and importantly, very quiet operation … no hum.

My home-made pickup winder.

 

 

The winder was fabricated from parts off a surplus 5.25” floppy disk controller. The pancake motor was removed and a flange fitted to hold pickup bobbins. Motor speed control was modified to run the motor at different winding speeds … from a few RPM to about 4000 RPM maximum. The head stepper was modified to steer the wire guide according to different scatter-winding patterns. A PIC processor controls the stepper motors and also keeps track of the actual number of winds.

 

Note the spools of insulated copper wire used for making the coils. The smaller spool is AWG 43 SPN and is used for the upper coil. The large spool is AWG 42 poly and is used for the lower coil. Obviously, the number of winds on the two coils are different --- they serve different functions.

 

To be added later: Comparative frequency-response curves for such pickups for those interested in the actual electrical specifications and  sample sound clips.

 

Although I’m not a big-time pickup manufacturer, on occasion I do a few special-order builds. If it’s something that pique your interest, let me know – we can always make a plan.

Technical Details

 

For sake of comparison, we’ll contrast the stacked pickups against a more conventionally-made set of single coil pickups.

 

 

 

Left: Stacked pickup set. Right: Conventional single-coil pickup set.

 

 

Pickups are fully wired with volume and tone controls and pickup selection switches as for typical installation in a guitar. These fully-assembled pickguards are part of my collection used with my Plywood Special guitar. (http://www.johanforrer.net/Guitars/PlywoodSpecial)

 

A 500K-volume pot and 250K-tone pots are used with the stacked set --- 250K volume and tone pots for the conventional single coils.

 

Both pickup sets presented here are intended as matched sets --- the bridge being the hottest, the middle and neck progressively lower in output. This is to accommodate differences in sensed string motions; the neck being subject to stronger/wildest motions. This arrangement also compensates for the bridge being more treble than the middle and neck. Some of these details will become evident in the frequency response plots below.

 

Measuring Pickup Frequency Response

 

 

 

Pickup frequency response measurements showing driver coil located above pickup. Stacked-pickup set shown.

 

A computer-controlled, swept-frequency method is used to acquire a pickup’s frequency response. The computer’s sound card is used to excite and measure electrical response. A low-impedance driver coil is placed in close proximity to the pickup sensing area and a sequential series of pure sine waves are applied to the driver. Response from the pickup is then measured and integrated and averaged over a brief interval. The frequency sweep typically covers approximately 10Hz to 20kHz.

 

To minimize additional loading affects due to the computer sound card, a high impedance FET buffer amplifier is used between the pickup and the sound card input. Note that measurements are taken in situ, with volume and tone pots fully open (at 10).

 

NOTE: Please keep in mind this kind of measurement is only to evaluate the electrical response of the pickup coil being subjected to a varying magnetic field. It gives the designer an opportunity to make educated guesses at a pickup potential. Typically, one can get an idea of whether the pickup would sound dark or bright, also judge how hot it will be. The actual sound of the pickup will greatly depend on the location and placement. That will affect how the magnetics interact, i.e., the type of magnet material, the magnetic orientation and strength, how far the magnets are from the strings, the kind of strings and their gauge. Pickups often exhibit a bit of microphony which will affect how much mechanical vibration gets transferred into he pickup itself.

 

Stacked vs. Conventional Single coil --- Frequency Response Plots.

 

Conventional Pickup Set Specifications:

Bridge  = 13.7K, 5.56H

Middle = 6.26K, 2.62H

Neck    = 6.21K, 2.54H

 

Stacked Pickup Set Specifications:

Bridge = 14.26K, ~4H

Middle = 13.50K, ~4H

Neck    = 13.68K, ~4H

Neck Pickups. Red=Conventional, Yellow=Stacked.

 

 

 

 

 

NECK: Similar responses are shown for these two pickups. The conventional single coil (RED trace) appears fairly flat across the spectrum. The stacked pickup shows a resonant rise around 5kHz that is an indication that it may have a more brightness. Typically, conventional Strat pickups shows similar resonant rise, however in this case it is suspected the 250K volume pot used on that particular pickguard is loading down and flattening out the resonant peak.



Middle Pickups: Red=Conventional, Yellow=Stacked.

 

 

 

 

Middle: Fairly similar across the board.

 

Bridge Pickups: Red=Conventional, Yellow=Stacked.

 

 

 

Bridge: Obvious differences being: output levels and high-end responses.

 

NOTE: This particular set of conventional pickups includes an overwound bridge pickup similar to the DiMarzio FV-1. Compared to the stacked sample, it shows a slight resonant rise around 5kHz region and a useful mid-range. The stacked sample shows an extended high end, however, not much high-end resonance boost. It also shows a useful mid-range hump. Typical guitar tone depends greatly on mid-range response … either accentuated or scooped depending on music style.

 

Example Sound Files

 

My rendition of “Wonderful Land” made famous by The Shadows.

In an attempt to keep most factors the same except for the pickups, the two pickguards shown above were fitted to the Plywood Special and the same amplifier and effects chain & settings was used. No editing or changes to the recorded tone or sound was made.

 

  1. Conventional single coil, overwound bridge

http://www.johanforrer.net/Guitars/OMF-Stack/Wonderful-Land-FV-1.mp3

 

 

  1. Stacked bridge

http://www.johanforrer.net/Guitars/OMF-Stack/Wonderful-Land-Stacks.mp3