Multi-Coil Prototype - Wal-Style Pickup For Guitar

[KhzDonut]

My background is 50% guitar & 50% bass, more or less. My first instrument was a bass, and shortly after had to play both for recording purposes.

I'm a big Tool fan, and Justin Chancellor has always been a big influence as a bassist. Consequently, I have more than a passing interest in Wal Basses, Multi Coil Pickups, and Filter-based Preamps.

My taste in guitar tones tends to run on the "dark" side, with lots of low-mid "chug" and a tight low end for the "djug" and then several other vague adjectives

Anyway, some of the qualities I've seen described by using multiple coils sounded like I could probably capitalize on a few of those qualities for guitar tones. I'm actually not 100% confident that it will fit my goal, but I have a feeling that it may work well for the technical/progressive metal acts that use a lot of tapping and articulation.

We'll see

I started out by testing to see what it's like to wind a mono-coil.




This is a .125" steel rod as a pole piece, the coil is a little under .350" tall, and bit over .400" wide. I got 10,000 turns of 44 AWG wire on the coil.

I'm planning on doing a taller coil and adding an insulator around the pole piece, and probably try 8-9,000 winds to start out with. Not sure yet. I also want to see if I could manage a standard .195" pole piece so I could use some off-the-shelf Alnico 5 rods.

To start with I'm using steel rods and varying sizes of neodymium discs (mostly .25" and smaller)

I've also got some .125" neodymium rods, but I'm anticipating them being significantly overpowered. Figured it was worth a fair test, at least.

A more typical coil geometry seems like it would be possible given tight-enough tolerances, but for rough prototyping the taller coils will give me a larger margin of error for getting the coils perfectly placed on a fabricated backplate. All I've got to drill with at the moment is a Dremel so it's a little hard to get things perfect.

My plan is to wire everything up like a more recent Wal, with each string being a "column" wired in series, and then each "column" wired together in parallel.

When this is finished I'll make another one where each "row" is wired in series as a unit, and each "row" can then be wired in either series or parallel like a standard humbucker.

[Richard]

I'm curious what you could do with a single row. It would be possible to tailor each coil to the string.

[big_teee]

The multicoil guitar pickup already exists!
They call it the ZexCoil!
Zexcoil® for Strat® ? Lawing Musical Products
T

[KhzDonut]

I'm concerned about microphonics, being into high-gain amps and music, so potting is definitely something I'm intent on getting right. I don't have access to a proper vacuum chamber ($$$) so I picked up a little manually operated vacuum thingamajig for testing break lines or whatever the hell (I'm sure someone who knows about cars could explain it) It doesn't do a full vacuum (30 inches of mercury or whatever) but I thought it will probably do a good enough job for wax potting, considering that many of the tutorials I've seen don't even mention vacuums, they just say to leave the coil in the wax for a few minutes.




I drilled a hole in the lid of a mason jar to attach the hose for the vacuum pump, and for the wax I just used some beeswax from a block I've had for the last 10 years. I know paraffin or a paraffin/beeswax mix is preferred, but I figured for testing purposes this would work fine.




I couldn't really take a picture of the process (I'll try to get one at some point) but the results were positive. I cut through the coil after it was potted with a dremel and an abrasive/cutting wheel, and the coil was solid *almost* all the way through. At the very center of the coil it started spitting out tiny bits of wire, which indicated to me that probably the last 10-20 layers at the center of the coil didn't get full wax penetration.

Still, I was pretty happy with the results. By reducing the amount of empty volume in the jar (by either putting in more wax or using a smaller jar) I should be able to get a better vacuum. I also thought about drilling a small pilot hole in the Forbon flatwork near the center of the coil so that there is a more direct-route for the wax to get to the center of the coil. I have a few other ideas if that fails, so I'm sure I'll figure something out

Super fun project so far.

[KhzDonut]

I'm curious what you could do with a single row. It would be possible to tailor each coil to the string.

That's what I'm hoping to do, though I'll have to do some testing to find out what direction to go with it. Taller coils, squatter coils, different number of turns, different gauges, etc... Still new to winding, so I have a long way to go.

The multicoil guitar pickup already exists!
They call it the ZexCoil!
T

I've looked at the ZexCoil, they're super cool!

They have a very different idea of how to accomplish the things I'm looking to accomplish, and I don't even think they make a "humbucker" style pickup, so in that sense my intent is to build a tiny-Wal pickup rather than a double-ZexCoil But I certainly am using some of their research as a basis for some of my design implementations.

[big_teee]

You can ask Scott, he is a member here.
He makes them.
http://music-electronics-forum.com/users/12330/

BTW, any pickup with 2 or more, even number of coils, can and are probably humbuckers.
T

[KhzDonut]

You can ask Scott, he is a member here.
He makes them.
http://music-electronics-forum.com/users/12330/

BTW, any pickup with 2 or more, even number of coils, can and are probably humbuckers.
T

Thanks! I appreciate the info

And yeah, I suppose a better description would have been "two-coil-per-string" pickup or "humbucker footprint" pickup.

I need to expand and refine my glossary of terms

[Steve A.]

...I cut through the coil after it was potted with a dremel and an abrasive/cutting wheel, and the coil was solid *almost* all the way through. At the very center of the coil it started spitting out tiny bits of wire, which indicated to me that probably the last 10-20 layers at the center of the coil didn't get full wax penetration...

Interesting project! I thought I'd point out that Enkay makes super heavy duty 2" cut-off wheels that are handy for a lot of projects. Dremel doesn't make ones that big because heavy use could burn up their tools. You do need to get their special mandrel which may require a larger collet.

Here's a listing at Amazon that looks very expensive compared to what I've been paying locally at Fry's (which offers free shipping for orders over $35.)

https://www.amazon.com/Enkay-288-2C-.../dp/B00MS35OZ8

FRYS.com | Enkay





Steve Ahola

[KhzDonut]

So I made a few sketches of how to wire all the coils together (they're messy and unreadable, so if anything this picture makes them look BETTER)




And in the process realized how much room I'd have to move coils around, which was much more than I expected. The tolerances are pretty tight side-to-side, but along the length of the string I could move things around quite a bit. So I did.



Just some old-school Forbon I cut with a Dremel and filed the edges smooth with some of the Stew Mac nut-shaping files. (Those things are fantastic)

The idea is that it keeps the coils under the thin/plain strings roughly the same distance/aperture as a normal humbucker, but narrows underneath the lower/wound strings.

I usually tune C standard with something in the ballpark of 12-56 set (for the br00talz and ye olde doomy stoner metal) so a focused low end is the order of the day. How much will this facilitate that? Who knows. Certainly not me. My one experience with a pair of Seymour Duncan Mini Rails led me to believe that a narrow aperture humbucker would sound focused, but it was in a Tele with an angled pickup that put the magnet underneath the lowest string the furthest away from the bridge, which does NOT facilitate a tighter low end.

So... Many... Variables...

But that's what empirical testing is for, so here we go

[John Kolbeck]

I've also got some .125" neodymium rods, but I'm anticipating them being significantly overpowered. Figured it was worth a fair test, at least.

I'd think for a bass, that would be no problem. Do you get "warbling" when bass strings are too close to AlNiCo 5 poles?

When this is finished I'll make another one where each "row" is wired in series as a unit, and each "row" can then be wired in either series or parallel like a standard humbucker.

I have thoughts on this: I don't see an advantage geometrically to using individual coils, and I think in the context of a guitar, it would exacerbate volume drop when you perform string bends (unless you do as Zexcoil does and arrange them at angles). I suppose it would increase the inductance a bit, since there will be a higher ratio of permeability material to air in the core. Though, higher inductance can be achieve other ways if that's what someone is looking for.

But there is a huge advantage: you now have eight inductors instead of two (or twelve if you do with with a regular humbucker) and so you can go well beyond series / parallel to combinations thereof, allowing you to get a multitude of inductances, voltage outputs and resonant peaks. The switching for that would be rather complicated though. I think it would make a great product if a company produced such a pickup, as well as the switcher that would be required to exploit various inductances.

[KhzDonut]

I'd think for a bass, that would be no problem. Do you get "warbling" when bass strings are too close to AlNiCo 5 poles?

Outside of my frame of reference, the only bass pickups I've used at length are EMG's and a Ceramic Seymour Duncan Musicman replacement.

...it would exacerbate volume drop when you perform string bends

That's one of the things where I've heard arguments go both ways, so I'm interested to see what the actual test results are. (Not that they'll be super scientific or anything) But I'm hoping that isn't a problem, and not really expecting it to be. Egg on my face if I'm wrong.

I think it would make a great product if a company produced such a pickup, as well as the switcher that would be required to exploit various inductances.

I've thought about what it would take to get proper switching, and the easiest way would be in something with a lot of access to control cavities, like a Jazzmaster/Jaguar or something with a lot of room under a pickguard to hide circuitry. You'd probably need to run a ribbon wire from the pickup to a separate board and maybe even go MIDI switching with it, because there's just sooo many connection. But I'm not really a circuitry guy, I just wire what the diagrams tell me to do most of the time. What little I know I learned from a year soldering and assembling pedals for a local FX builder, and that wasn't really much.

[KhzDonut]

The complexity of wiring a pickup like Wal does leaves me with a few challenges that, without more information about how Wal did it and how pickups are designed in general, lead me to believe that life would be really easy if I just had a circuit board printed. Obviously, that's a bit ambitious for a project like this :P

I took some brass eyelets, the vintage Fender ones that are usually used in making singlecoils with Forbon flatwork, and sanded them down so they'd be more like the solder terminals on a printed board. Mostly I just wanted them to be small so that they would be easier to work around.






The next challenge is figuring out how to wire the coil to the board, AND have connections going from each of those solder points to OTHER solder points. The inability to make actual traces is a problem. It would be a little tricky trying to solder the super tiny coil wire AND a regular sized wire in the same hole (and do it like 24 times)

So I had the idea to just run the copper wire used for the "traces" through the eyelets, and make loops for the coil wire to attach to. It's not elegant, exactly, but I think it should work.






Obviously it's not pretty, but the majority of it is a single piece of bent wire looped through a couple dozen holes, and then a few auxiliary pieces.

This way when I'm soldering the coil to the board, I ONLY have to worry about the coil wire. The rest of the wire is soldered into the eyelets, and should be very rigid and stable, even if part of the wire becomes loose/unsoldered during the process, it's connected elsewhere and should remain rigid and easy enough to work with.

It's a lot of work for a prototype, but the first time I was wiring things together on a Stew Mac Humbucker Kit I had some trouble with breaking the coil wire while trying to solder it to things (because I'm clumsy and kind of a pickup n00b) This seemed like an easy way to compensate for being meat-fisted and inexperienced.

I wouldn't want to have to build more than a few prototypes this way, though. It's a lot of work.

[big_teee]

So, if I read your diagram correctly?
Each pair of coils are in series, then all 6 pairs of coils in parallel?
If that is the case, then I would think you will end up with very low ohms impedance when they are wired together.
I've made 4 string bass 8 coil, multi-coils, and I wired each row in series then wired the two rows in paralell.
I still ended up with fairly low resistance pickups.
What are you trying to accomplish with this design?
Another observation, your coils will be extremely small, and I would predict, and hard to wind and make?
T

[KhzDonut]

So, if I read your diagram correctly?
Each pair of coils are in series, then all 6 pairs of coils in parallel?
T

You are correct, sir.

It's my understanding that this is how the most recent Wal basses are wired, and I thought I'd use it as a starting point.

The next one I do will be rows wired in series, then wired together using a 4 conductor wire so I can choose series/parallel with a toggle switch or push-pull pot, like a standard humbucker.

It will be interesting to see how the DCR reads on everything when it's all put together.

*checking numbers in some other threads*

Oh, well it turns out a lot of the information on "Number of Winds = DCR" info I've been using was actually something you posted in this thread:
http://music-electronics-forum.com/t36986/

4715 ohms of 42 will be in the neighborhood of 6200+ turns.
7500 ohms of 43 will put you up to around 7700 turns.
11500 ohms of 44 will put you up to around 9800 turns.
...
Take all 3 at 5000 turns.
42 @ 5000 turns = 3715 ohms
43 @ 5000 turns = 4700 ohms
44 @ 5000 turns = 5500 ohms

So I owe you one

I figured I'd aim towards what would be in the ballpark 18-9k dcr using 44awg, so 9,000 turns seemed a reasonable starting point. I figure I've got material for 5-6 prototypes, so if it takes me awhile to find what I'm looking for, I'm cool with that.

[big_teee]

The data you posted, that I did a couple of years ago?
That was for a PAF type bobbin.
That probably won't be valid for your bobbins.