Custom slanted guitar humbucker

 Goal : Design and build angled bridge position humbucker 

Specifications/Research :

    Currently, I have an instrument with a "slanted humbucker" route in the bridge position (humbucker is rotated 15 degrees or so as to mimic the tonality of slanted single coils found in strats/teles). This issue is that the pole piece closest to the bridge on the high e side of the pickup completely misses the string. This in turn massively attenuates the signal output of notes strummed on the high e; especially noticeable when the coil is split. To fix this issue, I am going to design and build a pickup whose 12 pole pieces are perfectly aligned with the strings. In terms of tonality, I would like it to sound something like a PAF or JB in humbucker mode and a strat-like clean single coil when split. The current setup in need of rectification:

Current setup with Seymour Duncan JB : pole pieces are not well aligned with strings

    The way I currently see it, my options are: 1. Using two prebuilt single-coil pickups and wiring/positioning them accordingly    2. Using two prebuilt single coil pickups with removed magnets; combining them in a new enclosure with a shared magnet    3. Design and build the pickup completely from scratch. For reasons of simplicity and time, I am going to try to exhaust options one and two before settling for three. 

    Repeatedly through this project, I continually referenced a couple main sources which you may find interesting if you want to build a humbucker yourself (or just want to understand them on a more fundamental level):

1. Seymour Duncan interviews Seth Lover of PAF fame
2. Basic rundown of hum cancellation
   
3. Magnet/Coil orientation and effect on amplitude/phase of output signal
   

Progress log: 

• 9-13-22 : I started investigating option #1 by rigging up two cheap strat pickups to measure ambient noise. I simply attached both pickups to a plank of oak, placing them as close as I could. The results were as follows:
• Single middle P.U. : ~30mV peaks, very microphonic
• Single neck P.U. : ~35mV peaks, very microphonic
• Aligned same way, positive of middle coil wired to negative of neck coil : Massive 5V at 4kHz
• Aligned same way, positive of middle coil wired to positive of neck coil : ~5mV average with ~10mV peaks
• Aligned oppositely, positive of middle coil wired to negative of neck coil: Massive 5V at 4kHz(seems to lock in to feedback loop, I'm unsure why the frequency is so high) 
• Aligned oppositely, positive of middle coil wired to positive of neck coil: ~6mV average with ~12mV peaks
• After further research, I realized some glaring errors in my process and mindset. Firstly, in some of my tests, the pickups were wired in parallel, not in series as intended for a humbucker. Secondly, I realized both my magnet orientations and pickup winding directions were already opposite; so simply attaching the south (middle PU) coil's positive to the north(neck PU) coil's negative and taking the output across the remaining negative and positive gave the result I was looking for(basically position 4 on a strat where noise cancellation occurs). With this setup, the output was markedly higher than the lone coils with a noise of around 10-15mV (reduction from single coil!). Useful image I came across for wiring:
  
  
  
• By this point, I had become pretty invested in making the pickup from the ground up (option #3); so I made a basic CAD model of what I thought the pickups construction should look like: two bobbins with ferromagnetic slugs over a base that would hold a bar magnet

  

  
  

  

  
  
  
  
• 9-27-23: My results and research from the previous session led me to the conclusion that making two bobbins with magnet pole pieces (like original strat PU's) and using a ferromagnetic bar to connect the magnets would decrease the number of necessary parts; the only downside being the pole piece height would not be adjustable(for some, this may be a sin but I've never once adjusted mine). This way, I can assemble the coils as I would single coil pickups; later fixing them to a base that magnetically connects the opposing magnets. I redesigned the bobbins so that the wire is as close as possible to the magnets. I also added holes in each bobbin for the positive and negative terminals of the coil. The results are as follows (north coil in grey and south coil in blue):
  
  
  
  
  
• 10-05-23: All along, I was planning to use a resin printer for the final version, for reasons of strength and dimensional accuracy. That being said, I used a standard 3-D printer for the first version of the coils; having to use and then remove organically generated support material. While the first set of bobbins were printing, I redesigned the baseplate, which I intended to attach the bobbins to through holes on each bobbin corresponding to dowels on the baseplate's face. For the rest of the baseplate, I followed a similar scheme to my first model except for the ferromagnetic bar. I realized I could use 1/8" steel and laser-cut 6 channels to connect the 6 magnets of the north coil to the 6 magnets of the south coil. The two advantages I currently see to this method are the recessed nature of the steel ( channels are held in solidly even without being glued ) and the reduction of volume/surface area of my connecting pieces (intended to minimize magnetic flux in non-ideal directions). The last thing I added was little channels on the bottom of the pickup so the wires wouldn't get squished. New baseplate modeled, I grabbed my first bobbins and printed my new prototype. So far, I was feeling pretty good about the results. 

  

  

                                                              
• 10-12-23: Imagine my horror when I held my bobbins to my guitar and realized the polepieces didn't even reach the high e string. Upon inspecting my CAD drawing, I realized the spacing for the bridge was incorrect ( I had the spacing as 53/6mm instead of 53/5mm). Unfortunately, this meant I had to redo much of my work. Other than the polepiece spacing, the only things changed from the last version were the addition of one more mounting peg in the middle of each bobbin as well as lettering to denote which coil is which. I printed this design but omitted the wiring channel because I'm considering putting a sort of lid on the bottom to enclose the wiring.                                                                                                              
• 12-10-23: After some small final tweaks to the design, I was ready try resin printing my parts. Unfortunately, many of my first attempts had issues with bed adhesion, dimensional inaccuracies, or both. I repeatedly had someone more experienced than me audit my process to ensure I wasn't doing anything wrong. Even though my first attempts at resin printing did not go to plan, I did eventually get a set of bobbins and baseplate to come out correctly. Next, I installed 12 un-magnetized slugs and my six magnet runners before dry-fitting the pickup together. While I was pleased with the look of the pickup, I realized my metal pieces were not interfacing perfectly and therefore breaking electrical/magnetic continuity. At first, I considered some sort of ferromagnetic glue or epoxy but glumly concluded that a major redesign was needed.

  

  

  
  
• 01-02-24: For my second attempt, I decided not to reinvent the wheel and start with a more traditional humbucker design. I started by remaking my model of both the strings and the cavity to continually ensure proper polepiece alignment. To simplify design and assembly, I decided to use adjustable polepieces for each coil connected by a single bar magnet. Another big difference from the first version is the use of brass machine screws to hold everything together as opposed to plastic dowels and glue. 

Full pickup with strings/cavity sketch superimposed

Pickup with south bobbin removed such that the magnet and metal spacer are visible

• 02-29-24: To verify my new design, I 3-D printed my new baseplate and resin printed my bobbins. Using a metal laser-cutter, I cut out the steel magnet spacers before painstakingly tapping all ten holes for each spacer. To assure I didn't have holes too large, I modeled the bobbins with slightly undersized holes. This means that after the print and cure, each hole in the bobbins required a small amount of boring to reach their final diameters. After assembling this version of the pickup, I was much more pleased with the design and durability of the unit. Now, the polepieces are properly magnetized without interruption. After making a final check of proper fitment and alignment inside my guitar, I decided to add aesthetic texturing to the top of the bobbins as well as small extrusions for the wires on the bottom. Finally, all that is left is to get the bobbins wound so I can finally hear what it sounds like!