Multi-Coil Prototype - Wal-Style Pickup For Guitar

[John Kolbeck]

You should be thinking about inductance targets anyway, which correlates with turns, and not DC resistance. You'd want to figure out what your final inductance target is, and then figure out what inductance you need for each coil based on the series/parallel combination you go with.

Frankly, I think you ought to just have all the coils in series so that any given coil can be of a low inductance, and you will end up with a high final inductance. In series, the values add together, so if you want a 3 Henry pickup, each of the twelve individual coils would only need to achieve 250 millihenries each, which is probably in the area of a 1000 turns of wire, depending on the core material. If you're into chugging bass lines, I imagine you'd want a rather high inductance, for a darker sound and higher output.

[KhzDonut]

That was for a PAF type bobbin.
That probably won't be valid for your bobbins.

I figured the DC resistance would vary a lot, but mostly I just wanted to use the information to reverse engineer the number of turns a Seymour Duncan Distortion had, because I knew the resistance and the wire gauge, so that gave me a rough estimate of how many turns I might be looking for as a starting point. I don't have a goal DCR, and I currently I don't know enough knowledge of things like inductance to use that as a predictive tool, so right now my goal is just to find a functional wind number as a starting point.

I know the Wal's are supposedly 10,000 turns per coil, and that some single coil guitar pickups are approaching that, and humbuckers range from PAF with 5,000 or so and high output humbuckers with ballpark 8,000. I used that information to speculate that doing 8-9,000 wouldn't be an unrealistic starting point.

But that's all I could figure out with my current knowledge of pickup design and the electrical engineering rules. I'm hoping to learn more about that in the process, so I appreciate the input a lot. I don't feel like I'm stabbing around in the dark, but I do kind of feel like I'm wearing sunglasses at night.

You should be thinking about inductance targets anyway, which correlates with turns, and not DC resistance. You'd want to figure out what your final inductance target is, and then figure out what inductance you need for each coil based on the series/parallel combination you go with.

Frankly, I think you ought to just have all the coils in series so that any given coil can be of a low inductance, and you will end up with a high final inductance. In series, the values add together, so if you want a 3 Henry pickup, each of the twelve individual coils would only need to achieve 250 millihenries each, which is probably in the area of a 1000 turns of wire, depending on the core material. If you're into chugging bass lines, I imagine you'd want a rather high inductance, for a darker sound and higher output.

I'll have to admit my complete ignorance of the affects of inductance on a pickup/circuit.

And my goal so far has just been to find a wind-number to start with. Any DCR that I've looked as is only to try to reverse engineer the number of winds on a reference pickup without having one on hand. No specific goal on a DCR to speak of, I know that how it's wired will change that number, which to this point has given me the assumption that it was something I could worry about fine-tuning later. Hopefully that was not an incorrect assumption

I really appreciate the input, as I said above, I feel like I'm flying a little blind on this and hoping for the best. New knowledge is very appreciated.

[John Kolbeck]

I'll have to admit my complete ignorance of the affects of inductance on a pickup/circuit.

And my goal so far has just been to find a wind-number to start with. Any DCR that I've looked as is only to try to reverse engineer the number of winds on a reference pickup without having one on hand. No specific goal on a DCR to speak of, I know that how it's wired will change that number, which to this point has given me the assumption that it was something I could worry about fine-tuning later. Hopefully that was not an incorrect assumption

I really appreciate the input, as I said above, I feel like I'm flying a little blind on this and hoping for the best. New knowledge is very appreciated.

The inductance determines the resonant peak and the output voltage for a given input current. When you have a "hot" pickup, the DC resistance just so happens to be higher more often than not, but it's a higher inductance that actually makes the pickup "hot". When you combine inductors in series, the inductance adds together

You said the Wals were 10k turns per coil, with pairs of two in series, and a total of six pairs in parallel. Let's suppose each coil is 4 henries as a result of the 10,000 turns. Each pair of two combines in series to become 8 henries. If you now think of it as six inductors in parallel, 8 henries each, the end result will be only 1 henry (which will make for a low output, and very bright sound). You can use an online calculator to figure out what values different combinations will result in very quickly Inductance in series and parallel Calculator - High accuracy calculation . Just as a point of reference, a typical Fender P Bass pickup is about 6 to 7 henries, while the Jazz Bass pickups are about 3 to 4 henries. Which is also to say, I don't think you will be pleased with the result of your pickup as it's currently configured, and you might want to consider having more of these coils in series.

Since adding together inductors sums their inductance, series wiring is the most economical way to achieve a given resonance target (hence why nearly all humbuckers are wire in series), and saves you a lot of time winding, saves space, relieves you from having to use tiny wire which breaks more easily than heavier gauge wire.

You can make educated guesses as to the inductance by calculating it from the wind count, but if you want to get serious with precision, you can get an Extech 380193, which is known to work good with guitar pickups.

[KhzDonut]

The inductance determines the resonant peak and the output voltage for a given input current. When you have a "hot" pickup, the DC resistance just so happens to be higher more often than not, but it's a higher inductance that actually makes the pickup "hot". When you combine inductors in series, the inductance adds together

You said the Wals were 10k turns per coil, with pairs of two in series, and a total of six pairs in parallel. Let's suppose each coil is 4 henries as a result of the 10,000 turns. Each pair of two combines in series to become 8 henries. If you now think of it as six inductors in parallel, 8 henries each, the end result will be only 1 henry (which will make for a low output, and very bright sound). You can use an online calculator to figure out what values different combinations will result in very quickly Inductance in series and parallel Calculator - High accuracy calculation . Just as a point of reference, a typical Fender P Bass pickup is about 6 to 7 henries, while the Jazz Bass pickups are about 3 to 4 henries. Which is also to say, I don't think you will be pleased with the result of your pickup as it's currently configured, and you might want to consider having more of these coils in series.

Since adding together inductors sums their inductance, series wiring is the most economical way to achieve a given resonance target (hence why nearly all humbuckers are wire in series), and saves you a lot of time winding, saves space, relieves you from having to use tiny wire which breaks more easily than heavier gauge wire.

You can make educated guesses as to the inductance by calculating it from the wind count, but if you want to get serious with precision, you can get an Extech 380193, which is known to work good with guitar pickups.

Thanks for the information, your previous post makes a lot more sense to me now. I see now that I was missing/not understanding some things. (And still am, honestly)

If I'm understanding you correctly, if I wanted to have this wiring configuration reach the desired inductance I'd have to have enormous numbers of turns, or I could have less turns and change to series wiring across the board (and that would, in your opinion, be the much more sensible approach)

I'll finish out this one just to have as an empirical reference because I've already gone this far on it. But thanks for the recommendation, I wish I could have started an all-series pickup first.

I'm finishing up some work bench re-organizing so I'll try to get to winding the coils in the next couple days. Maybe I'll just build both pickups in tandem and finish them together.

[John Kolbeck]

If I'm understanding you correctly, if I wanted to have this wiring configuration reach the desired inductance I'd have to have enormous numbers of turns, or I could have less turns and change to series wiring across the board (and that would, in your opinion, be the much more sensible approach)

That's right. Another example, you could make a parallel wired PAF sound like an ordinary series wired PAF, but instead of two coils producing 2 henries resulting in a total of 4 henries in series, as is typical, you'd instead need two coils of 8 henries that then became 4 henries in parallel. That would probably require filling the bobbins to the max with 44AWG, if not requiring a taller bobbin to hold all that wire. The only humbuckers I know of that are intended to be wired in parallel are Seymour Duncan Vintage Rails, and I think it might be because they simply reuse the coils from their Cool or Hot Rails model, wiring them in parallel instead of series in order to achieve "vintage" output.

I'll add for the sake of completeness, that when you wire a pickup in parallel, you divide the inductance, but you then compound the parasitic capacitance if the coils. A higher capacitance brings the resonant peak down (as does a higher inductance), so the arithmetic is not quite as straight forward as the first paragraph makes it out to be. Having said that, parallel mode still results in a much higher resonant peak than series, for a given set of coils.

[Jason Rodgers]

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.

[ATTACH=CONFIG]40540[/ATTACH]


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.

I applaud your sense of adventure. I dove into winding with a notion to find the next awesome sound by experimenting with bobbin types, core types, different wire gauge, different magnets... all in the same pickup! Well, I certainly got a sound, but I don't know why. Now I need to back up and try something a little (or a lot!) more "traditional", or at least "tried and true." This seems to be my MO, and clearly I haven't learned, aside from knowing that I'm completely comfortable barreling headlong into the unknown. So in that sense, I get where you're coming from.

While any listening that needs to go through your device and speakers or earbuds is imperfect, I've been pleasantly surprised by these pickup demo videos from SD. https://www.youtube.com/watch?itct=C...DM&app=desktop
I've been watching them, finding my own adjectives to describe each, and then looking at the specs to find correlations between physical construction and sound. I'm nowhere near a point in my winding where I can say, "I want to hear a little more of 'X,' so I should wind/build like this..." What I'm finding is that I'm surprised at how many pickups are typical slug and screw coils, about 8-10k DCR, with ceramic magnets, and so much variety in sound!

Anyhoo, I do not discourage your R&D, just my observations on my own search for the next best thing.

[KhzDonut]

Been a bit delayed on working on this, for a couple reasons.

1. Still figuring out how to manufacture lots of the little "discs" out of the Forbon. It has proved difficult to be precise. I think I've found a solution, but I will be unable to work on it for a day or so. Life gets in the way :P

2. Wiring.

It was pointed out that wiring all the "columns" in parallel would probably result in low output, and from what I can find about the Wal Bass pickups, is that this sounds like a feature of the design in their model, and it is my understanding (though I can't be absolutely sure I'm correct) that the Wal preamp takes all of the individual "column" inputs and "sums them electronically," which is how I've seen it described when combining the coils of an EMG or Blackout pickup and wiring them "in parallel" to the preamp.


This is where I am very out of my element, and if anybody had more information and was willing to explain it, I would be eternally grateful.

The assumption I'm running with right now is that for a preamp to sum 6+ "columns" of coils together, it would have to be a design that HAD that many inputs, so just buying the Seymour Duncan Blackout Preamp off the shelf would probably be an insufficient solution:

Blackouts Preamp ? short shaft | Seymour Duncan


I've had trouble really finding an explanation of this process using Google, though I'm assuming that's because I'm not sure of what I'm even asking, and my search terms are insufficient.


In the meantime I will probably build a more conventional prototype, or one with only 2 "columns" (so a quad-coil, or I guess a double split-coil)

[rjb]

Still figuring out how to manufacture lots of the little "discs" out of the Forbon. It has proved difficult to be precise.

I think this method might work- although it won't win any efficiency awards:
Clamp the forbon to a drill press table. Drill a center hole. Without moving the forbon, replace the drill bit with a plug cutter*; drill the disc perimeter. Now you should have one disc with a centered hole. Repeat moving & re-clamping the forbon, and swapping the drill bit and the plug cutter until you run out of patience. Go play guitar for awhile, come back and continue making discs.

* Plug cutters look like this 4 Piece Plug Cutter Set

I think I've found a solution, but I will be unable to work on it for a day or so.

Please report back when you do.

The assumption I'm running with right now is that for a preamp to sum 6+ "columns" of coils together, it would have to be a design that HAD that many inputs,

Is this helpful?
Summing Amplifier is an Op-amp Voltage Adder

[big_teee]

If the little disks, are for the bobbins?
Why not order some fiber washers.
There are scads of them in small sizes.
https://www.amazon.com/uxcell%C2%AE-...=fiber+washers

[rjb]

If the little disks, are for the bobbins?
Why not order some fiber washers.

D'oh. How obvious was that?

Duh,
-rb

[David King]

Yeah you certainly don't need them to be forbon, fishpaper would suffice and save space.