Adventures in Exotica: My Neodymium Multi-Coil Sidewinder Project

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Let’s Start From the Beginning…

Over the last couple months, I’ve been immersed in developing my neodymium multi-coil sidewinder pickup. The idea was to make a bridge pickup that can do it all, but take up a smaller space than a traditional pickup. I figured that the entire width of the pickup would be used a the sensing area as there are no coils wrapped around the poles. It seemed to do the job pretty well. The relatively large neodymium magnets reproduce a lot of bass, while the naturally extended highs of the sidewinder design work together. I voiced a little onboard preamp to bring it up in a live band situation.

The Funktronic Multi-coil Neodymium Sidewinder
Various Stages of the Exotica Pickup

 

Building the Exotica Pickup

The Base Plate

Machined aluminum prototyping base plate to hold the multi-coil assemblies
Bruce at X-strange machined this block

The first two big problems to solve were the small amount space for the multi-coil assembly and keeping the magnets from crashing into each other. The neodymium magnets are really strong and somewhat difficult to manage. So, I designed a little base and had Bruce over at X-Strange machine a master that I could use for prototyping. The base has little trays built in that I could use to place the magnet assembly. I had to use a combination of press-fitting and glue. From there, I came up with a design for my bobbins. The trick was to be able to fit the terminals within the walls of the bobbin itself.

The Bobbins

Micro coil with polyurethane bobbin and copper wire
Little bobbins for little sidewinders.

The bobbins are a combination of cast polyurethane and paper. I file grooves for the wires and attach them with CA glue. I figured that once they get encapsulated inside a block of epoxy, the paper and CA clue will be strong enough. They are pretty fragile, however t I only had one actually fail during the prototyping process – and that was purely due to operator negligence.

 

I wound these on The Funktronic Coil Genie.

The Cover

Hand made nickel silver pickup cover
Capped with nickel silver

I encapsulated the pickup in white polyurethane, but I wasn’t happy with the results. So, I bound and capped it with some nickel silver scraps I had laying around. Using various cements to affix the metal, I had better luck with the softer adhesives like E6000 or Gorilla Glue. For some reason, CA or epoxy wouldn’t hold the metal down. I’ve never had that problem – usually epoxy will do it.

 

After gluing, I soldered the cap to the binding with my soldering iron. In another life, I used to solder little structures like this all day long. Back then, I used a propane or oxy-acetylene torch. This was the first time I’ve done it with a soldering iron. It wasn’t too bad! The nickel-silver is really forgiving; I had a sand-through that I patched with a blob of solder (it’s really thin metal). Once you sand it, the patch is barely perceptible. At the very least, my cap and binding job will provide some shielding.

 

 

Putting it All Together

 

Despite the seemingly complex multi-coil assembly, the build process itself was pretty straightforward. It’s really a long series of many simple steps. Here’s a few images of the assembly process.

 

 

 

Funktronic Multi-coil Neodymium Sidewinder Pickup with nickel silver cover
Voila! A shiny pickup!

So far, my preliminary have been promising. It sounds really good! I’m really anxious to get it installed in a bass so I can test it out in the field.

 

This Week’s “Bass of the Week” in NoTreble

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Cool! Looks like the Modelo Uno has been featured in NoTreble.com! There’s nothing quite like seeing your work featured in a publication. Now that’s what I call excitement!

Bass of the Week: Sirena Modelo Uno

This week we’re checking out a funky and cool bass built by Jeremy Kirsch called the Sirena Modelo Uno. The four-stringer takes its design cues from similarly funky vintage basses.

New Preamp and Pickup Wind

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OK I’m just going to post a weekly update – no pix today.

I’ve been working on the pickup and preamp. Using my new cardboard bobbins I wound a couple of coils with 44awg wire and increased the wind count. I after casting them I mocked up a pickup with the new ceramic 8 cores. From there, I rebuilt my preamp using a James tone stack instead of the Big Muff/Tilt tone stack.

Two things:

1) On one of the cast bobbins, I somehow didn’t add enough hardener to the epoxy resin. I think that’s a pitfall that comes with mixing tiny 10ml quantities – if you’re off by just a tiny bit, that turns out to be a lot. Anyway, the piece didn’t cure and came out kind of rubbery. It’s good enough for testing, but not for a finished pickup. In the process of experimenting with various ways to build and cast my modular coils, I used all the pre-cut cardboard flatwork (I only ordered 14 pc to start). I ordered some more – it should be on its way soon.

2) I changed the preamp to a James/Baxandall tone stack because while the one-knob preamp was kinda cute, there just wasn’t any real control over the tone. Once you added any treble, you started to cut bass and vice-versa. With the James/Baxandall I’m able to fine tune the amount of highs and lows. I was even able to fine-tune the circuit itself by bumping 400Hz up by about 2dB. I also upped it to 18v much more headroom.

I know I’ve said this before, but this new pickup and preamp combo is a huge improvement. Keep in mind, pickup design is kind of a long process of experimentation that isn’t all that straightforward. In any case, the C8/44awg sidewinder rendered a much more controlled-sounding pickup. No more crazy high mids from the neos and with the ceramics wrapped in all that stainless steel, the biting highs are in the right place – nicely placed on top of a big cushion of clear lows and warm mids. With the neo versions, I felt like I was always struggling to contain this beastly pickup with these upper mids that just didn’t want to behave. Now I can really dig in to the strings without having to worry about it topping out.

I think it’s possible to design a really good-sounding neodymium pickup. I don’t know that the sidewinder design is the best application. I think maybe a more conventional humbucker with a steel core and the magnets placed on the bottom of the pickup might be a better approach with the neos. That keep the super strong neos away from the strings would make the magnets have to permeate all the way through the steel core. I dunno, just theorizing.

Funktronic News | August 24, 2017 Weekly Update

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This week was mostly busy work. Most noteworthy, I took a few beginning steps to start a small production run of my Neodymium Sidewinder Bass Pickup. I dropped off some drawings of the parts with Bruce over at Johnson’s Extremely Strange Musical Instrument Company. Bruce is going to machine some nice masters that I can use to make molds for my parts. Basically, I decided that I have reached the point where I want to refine the design of my pickup and develop my production model. In the meantime, I’ll call around and get some quotes for getting the blades water-cut out of 430 stainless. I will start off with a few samples and see how they work with the molds. I’m feeling excited about it and I think it will be good to “finished” with my first design. As things progress, I’m sure I’ll be more excited about it.

On another note, I tried to take a few days off and give my brain a rest from pickup making. However, I failed spectacularly and came up with a drawing of a new sidewinder pickup that I think I can make reversible.

Neodymium Sidewinder Bass Pickup Progress – Pieces Cut and Partially Assembled

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I didn’t want to jump the gun and reveal my progress with this pickup build too early, but at this point I have more than a year into this design and after today, this felt pretty good. Besides, I prolly won’t get to the ears and the base until Sunday. Here’s an image of my neodymium bass sidewinder pickup:

partial assembly of the Funktronic neodymium sidewinder bass pickup

I sanded and polished the epoxy parts. I basically sanded it up to 2000 grit. It polishes OK, but I don’t know if I can get it up to a gloss. I think that’s where CA glue would come int. The bars are just roughly sanded and need sanding and polishing. I’ll get to that this weekend as well. I’m really envisioning them in chrome.

Once I cleaned up my epoxy resin cast bobbins, they looked pretty good. I’ve been talking a lot of smack about Garolite as a bobbin flange material lately, but I gotta say it worked great. It feathered right into the epoxy.

cast epoxy bobbins and coils sanded and cleaned up

In addition to the base, my next big quandary is going to be this: I’m going to need to “pot” the space in between the coils and the bars. I left about .005″ gap on either side – not a lot, but enough to see daylight through it. There has to be some space in order to assure that the magnets are making full contact with the bars. We’ll see. Dripping the clear penetrating epoxy sealer would make kind of a mess. I don’t know if I even want to think about pouring potting wax in there.

Spin Doctor: Resin Casting the Coils for the Bass Neo Sidewinder

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For this pickup, I had to come up with a way to cast a fairly narrow coil in epoxy. I had to do it in such a way so that the magnets would not be covered in resin and the bottom needed to have space for the wire terminals. What I decided to try was to make a two-part silicon mold and cast the coils without the magnets so that I could install them later.

First, I made a two-part mold. This basically involved making one cast using modeling clay as a filler. I used ball bearings as registration points.

Two-part silicone mold used in molding Funktronic Bass Pickups

I backed one edge all the way to the side of the box.  Leaving on side open, this is where I will actually pour the epoxy into the mold. The wire terminals will be sticking out of the back. Once I poured the Smooth-On OOMMOO 30 silicone casting compound and let it set, I got this:

Smooth-On silicone molding compound used in molding Funktronic Bass Pickups

From which I made the other half of the mold – I’m actually making a couple of different parts here…

Smooth-On silicone molding compound used in molding Funktronic Bass Pickups

Once I go the completed mold, I placed the coil into the mold. I included a couple of nubs to hold it in place so that the coil is suspended in the mold while the epoxy flows underneath it. It’s tight enough so that not too much resin goes into the slug holes, but just in case, I added some registered drill marks that would be cast into the piece. This coil hasn’t had the terminals installed yet – I just placed it in there for demonstration.

Next, I pour the West Systems Epoxy. I used black Mixol as a colorant. I ended up mixing a little too much epoxy – the whole cast only used 1/2 teaspoon of material! The fixture is to keep the sides from flexing – otherwise, the epoxy will just splooch out of the sides. Note the li’l terminals sticking out of the top left corner.

Casting the Funktronic Neodymium Bass Sidewinder coil in Black West Systems Epoxy in a silicone mold

And here we go!

Not too bad! First, let me disclose that there was a teeny weeny bit of resin in a couple of the holes – I just got too excited and cleaned them out before I took the picture. The sides might need a little sanding and cleanup, but they won’t be exposed, so I don’t have to worry too much about it. I will have to do some facing on the top part which will be visible. I had the casting in the mold for about 8 hours on a fairly hot and humid day, and the epoxy still seemed a tad soft. I may let it harden for another day before I start sanding the front surface.

Next up, the dog ears and base.

Spin Doctor – New Smaller Bobbin!

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I wound the new bobbin with the more closely spaced poles the other night – definitely a better approach than building the bobbin around the neodymium cores. Basically, I glued the blank flanges to the keepers and using the keepers as a drill template, I bored the holes in the blank flanges.

They came out pretty good! I think that drill schedule will work better. It certainly took a less time. Casting and sanding the keeper is still taking a while. I’ll have to work on that. I had a little more trouble with flaring. I think having the magnets in there added more gluing surface. If this magnet-less winding procedure works, I might look into making another plate for the winder that sandwiches the bobbin in there so it won’t flare.

Next, I epoxied the wire terminals to the bobbins.

I used those breakaway header pins. You can’t beat ’em for cheapness or convenience, although I’m still troubled by this joint; when I solder, the housing heats up enough for the wire to loosen. It hardens back up as it cools, but I can see this being problematic. I’m going to look into making some little mount out of stripboard and try using the right-angle pins instead.

Next stop: epoxy encapsulation!

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