Building custom pickups

[Sadie-f]

(btw, best holiday wishes all!)

I've thought about this a good long time and partly because the pickups I would buy for a new build are for now on indefinite backorder (like 6 months +) .. time to think about doing it the hard way.

My aim is to build HB's with rare earth neodymium magnets, and I'm considering winding each pole piece individually.

Neo magnets are about 10x stronger, so I'd expect I can wind 10x fewer turns for the same signal at lower resistance and inductance.

Also, as I understand it, the closer the windings are to the pole pieces, the stronger the interaction, and so that ought to be an added benefit of both winding on a smaller core, and needing less total wire. In transformer calculation, we think of number of turns count, not total length of wire.

I'm not completely married to individually winding for each pole / string, however another potential advantage I see would be tailoring to the different output inherent to smaller / larger strings & wrapped vs bare as well.

Winding count is easy for me to setup, I've got plenty of stepper motors / controllers, so the only investment would be in a bobbin holder.

The potential downside I can imagine might be excessive brightness in the sound, I'm prepared to do some experiments to look at that, and working a single coil at a time, it would be pretty easy to gauge effect, both as qualitative and quantitative.

Thoughts?

 

[ragamuffin]

To me it sounds like it would be quite a challenging and potentially frustrating exercise, and the results would be pretty unpredictable.

Buuuuuut, anything is possible and it could be quite the journey!

Personally I'd just buy a nice set of pickups (they don't have to be expensive), but if you're up for a wild ride why not give it a shot?

Happy Hollidays!

 

[TBurst Std]

I’d say try it if only for the learning gathered.  You obviously have the skills to avoid most mistakes. In addition, it sounds like you are thinking of somethings that are not readily available or done.

 

[Sadie-f]

I’d say try it if only for the learning gathered.  You obviously have the skills to avoid most mistakes. In addition, it sounds like you are thinking of somethings that are not readily available or done.

This is my take . To be sure, the PUs I can't get are Q-tuner splittable 4 wire, which I think are the right idea, and who knows, could also rightly suck.

If I try building from scratch and don't love the results, then my next choice will be a set of Lollar dB HBs with alinco 8 at bridge & 5 at neck. These are said to be quiet remarkable.

I'm not convinced I can improve on either of these, on the other hand, I know I'll enjoy trying .

 

[Lbpesq]

Cycfi Research (cycfi.com) makes individual neodymium pickup capsules like you are describing.  Never tried them myself, but they do look interesting.  I’ve heard great things about the Q-Tuners.  I have a set that I’ll mount in one of my guitars one of these days when I have the time.

Bill, tgo

 

[mayfly]

Hey Sadie,

you know what, if you take this on and make it work (after likely several attempts) you will probably end up being the resident expert of pickups here on the board.

Having said that, I don't have much to add except this is a good place to buy pickup parts:

https://nextgenguitars.ca/categories/guitar-bass-parts/pickup-parts-winding.html
https://nextgenguitars.ca/categories/guitar-bass-parts/pickup-covers-mounting-rings.html

 

[Sadie-f]

Hey Sadie,

you know what, if you take this on and make it work (after likely several attempts) you will probably end up being the resident expert of pickups here on the board.

Having said that, I don't have much to add except this is a good place to buy pickup parts:

https://nextgenguitars.ca/categories/guitar-bass-parts/pickup-parts-winding.html
https://nextgenguitars.ca/categories/guitar-bass-parts/pickup-covers-mounting-rings.html

Thanks for the links, those are handy! I'm sure I won't be the expert, outside of the specifics I want. I'm sure taking measurements to understand magnet / coil design and frequency response a little better, using both alinco and neo magnets will help more quickly decide if there's something to be gained.

 

[Sadie-f]

Cycfi Research (cycfi.com) makes individual neodymium pickup capsules like you are describing.  Never tried them myself, but they do look interesting.  I’ve heard great things about the Q-Tuners.  I have a set that I’ll mount in one of my guitars one of these days when I have the time.

Bill, tgo

Oh, that's a nice resource! It's not the only place I've seen per-string windings, and I wouldn't be wild about the active design, however it's great to see someone going in that direction, and they've got an awesome design there! Plus I like the open source approach, the whole design being available to learn from and compare has to be a good thing.

When you get your Q-tuners installed, give a shout! I'll be interested to hear your experience.

 

[Sadie-f]

Since it's what I've liked best so far, I looked at high-wind HBs and found that sure enough, at very high calculated inductance, they can form an LR low pass filter, and that's before adding in the capacitance that's also a present (but I haven't analyzed it because I don't know how to measure or calculate that).

So this explains how high wind + output HBs can lose some top end clarity (especially if connected to a lower input impedance amp input).

Here's an article I found,  super helpful take away quote

the magnetic field comes up to the stings there and magnetizes the strings. That’s one of the things that most people don’t understand. They figure that string is waving there and cutting the magnetic lines of force. Nuts. That isn’t it. The magnet, all it does is magnetize the string. Now you’ve got a waving magnetic field. And we have a fixed coil with a waving magnetic field to induce voltage.

https://www.guitarworld.com/gear/how-does-a-guitar-pickup-really-work

Going by this .. short of permanently magnetizing strings (1), there's no way around balancing between enough magnet field strong enough at the string to generate a good signal and being too close, and diminishing sustain(2). I'm hoping what I find is that there's a simpler approach of instead of having the pole pieces be closer, make the windings as close as possible to the string.

1. How cool would it be to permanently magnetize the strings to use a magnet free coil?

2. I've always been a little dubious on this. It seems to me that oscillating within a magnetic field, in and of itself does no work, so there should be no effect on sustain. On the other hand, if the signal does work (i.e. if there's low enough resistance in the circuit, or capacitance / inductance can sink current, then work is done and sustain would definitely be affected). Modern amps have > 1 MOhm input resistance.

 

[JohnnyHardtail]

1) IMO its slightly simplistic to say the pickup operates just because "string is magnetised", even if its the basic truth.  Its more useful to look at the concept of a "magnetic circuit" where the magnetic flux has to flow though the magnet via the string and via both poles of the humbucker as a complete loop.  The magnetic field of the pickup is disturbed by movement of the magnetised string.    It wouldn't be possible to create a string that is strongly magnetised by itself, as the material properties don't allow for it.

2) Whenever there is a varying magnetic field, magnetic induction will occur.  It not only induces current in the windings of the pickup.  It also induces unintended currents in every single metal component, such as brass or nickel-silver baseplate, alnico magnetic cores, or steel pole pieces etc.  This unintended induction causes "eddy current" loss.  That is one source of losses that affects the magnetic circuit and causes a loss of sustain.  The "eddy current" losses also reduce the resonant peak of the pickup, making it sound less bright.  That is why people sometimes say that a brass baseplate gives a humbucker warmer tone than a nickel-silver one.  Same applies to the metal alloys used in the pole pieces.

3)  There is also an aspect of magnetic materials called "hysteresis loss".  Its due to the way a magnetic material responds in changing magnetic field according to its "magnetisation curve".  It causes a cyclical delay or phase shift of instantaneous field strength when the string is vibrating, so it is a further reason why sustain is affected by strong magnetic fields.  I understand it results in a reaction force that is out of phase with the string vibration causing the dampening effect.

 

[Sadie-f]

1) IMO its slightly simplistic to say the pickup operates just because "string is magnetised", even if its the basic truth.  Its more useful to look at the concept of a "magnetic circuit" where the magnetic flux has to flow though the magnet via the string and via both poles of the humbucker as a complete loop.  The magnetic field of the pickup is disturbed by movement of the magnetised string.    It wouldn't be possible to create a string that is strongly magnetised by itself, as the material properties don't allow for it.

For the moment, I'm just going by the article, that quote is Seth Lover and what I didn't include is his claim that you can "If you want to, take the magnet out. One you’ve magnetized your strings, it will play until the string loses it."

I think that's off on two points, first you're correct that the total permanent magnet strength achievable in steel / nickel wound wire is low and I expect far lower than what's needed to work well in generating a signal. Also, he's wrong in thinking that the string would lose it's magnetism. Until you specifically demagentize a ferromagnetic material, that's permanent.

To me the useful way to look at it is the one that's physically correct. I'm inclined to think Lawing / Lover and the national magnet lab are correct. However improving on the experiment outlined int the article isn't going to be that tough, so I'll be aiming to do that. I see two key potential sources of error in Lawing's procedure / assertion.

The first would be that while they evaluated the magnet-free P/U by "it sounds the same". It's not that hard to hookup to an oscilloscope and observe signal decay for a quantitative, measure. Listening to the sound is an obvious possible confirmation bias.

Second, the magnet-free PU still had pole-pieces, which are still part of the magnetic circuit (albeit direct contact of magnet -> pole piece --- vs magnet, pole piece, gap, string, gap, pole piece *ought* to be far lower circuit coupling *ought* to be an audibly lower signal .. we still can't fully discount confirmation bias, or the unstated gap distances.

Again, this should be easy to incorporate into an attempt to replicate / improve on the rigor of the Lawing experiment.

2) Whenever there is a varying magnetic field, magnetic induction will occur.  It not only induces current in the windings of the pickup.  It also induces unintended currents in every single metal component, such as brass or nickel-silver baseplate, alnico magnetic cores, or steel pole pieces etc.  This unintended induction causes "eddy current" loss.  That is one source of losses that affects the magnetic circuit and causes a loss of sustain.  The "eddy current" losses also reduce the resonant peak of the pickup, making it sound less bright.  That is why people sometimes say that a brass baseplate gives a humbucker warmer tone than a nickel-silver one.  Same applies to the metal alloys used in the pole pieces.

3)  There is also an aspect of magnetic materials called "hysteresis loss".  Its due to the way a magnetic material responds in changing magnetic field according to its "magnetisation curve".  It causes a cyclical delay or phase shift of instantaneous field strength when the string is vibrating, so it is a further reason why sustain is affected by strong magnetic fields.  I understand it results in a reaction force that is out of phase with the string vibration causing the dampening effect.

Thanks, and damn right about eddy currents, I hadn't factored that in my thinking **thanks** (and magnet hysteresis is a part of it for sure). unfortunately, that's harder to separate out in testing, OTOH, it's essentially a constant and I could evaluate it using a low-wind magnet, the winds can quantify sustain / decay, while a neo magnet is obviously a good choice for generating high eddy currents in the string.

In transformer cores and motor winding cores, manufacturers have long used silicon steel which has ~5x lower conductivity than regular steel, a relatively recent addition to core steel plates is the use of glass / amorphous steel plates which offer yet another 3 x better efficiency, because they remain ferromagnetic but are fundamentally non-conductive. Not easily adaptable to guitars, as neither form is well suited to wire drawing.

 

[mayfly]

Following this thread with interest.

 

[Sadie-f]

Following this thread with interest.

Not too interesting yet, I did receive the first batch of neodymium magnets yesterday, and moving the N pole close to the string of a single coil definitely increased volume until getting too close where it attenuated (probably eddy current damping?).

Reversing to s->n orientation, at a certain distance, but still not greatly damping oscillation I could effectively silence the string between the magnets. Also cool.

One could make a really cool effect sliding magnets into proximity, geometry wouldn't be easy.

 

[Sadie-f]

Interesting first winding test. With only 6' of 44ga (64 ohms) wire wound on a 3/32 neo magnet, I read about 2-2.5 mV of AC signal. My 8k ohm bridge HB, 6k middle foil, and 18k bridge HB all generate 50-150 mV, depending on the string.

That would suggest at a mere 4k ohms for 6 strings (individually wound) I could get on the order of the same signal level.

Of course, question remains, will it make the sound what I want?

Anyway, a promising start

 

[mayfly]

Hey!  I've seen that before!  Someone in the 50's tried that to get a hex pickup (and ran all 6 channels separately).  Apparently it worked.  There was an article in guitar player back in the pre-internet days.  And of course my internet search brought up nothing on it ... 

 

[stratamania]

For reference you might want to check out Zexcoil pickups who use an individual coil per string. I guess Zex is a play on words for Hex.

 

[Sadie-f]

For reference you might want to check out Zexcoil pickups who use an individual coil per string. I guess Zex is a play on words for Hex.

Yep, I've looked at zexcoil, their approach to alternating polarity as a means to cancel emf hum is part of my plan.

 

[Sadie-f]

Hey!  I've seen that before!  Someone in the 50's tried that to get a hex pickup (and ran all 6 channels separately).  Apparently it worked.  There was an article in guitar player back in the pre-internet days.  And of course my internet search brought up nothing on it ...

Yep, there's a few over the years done this way. The first obvious production hassle is instead of soldering to 2 sub-40 ga wires, you have to make a dozen of those connections. It's about half the diameter of human hair, it's a serious pain to handle .

 

[stratamania]

For reference you might want to check out Zexcoil pickups who use an individual coil per string. I guess Zex is a play on words for Hex.

Yep, I've looked at zexcoil, their approach to alternating polarity as a means to cancel emf hum is part of my plan.

Ok, hope you get somewhere with the experiments.

 

[bostjan]

I wish I saw this thread earlier.

I've made my own pickups a number of times.  I never made anything that sounded better than what I could buy off the shelf, but alternating polarities to make a humbucker in a single coil (per string) fashion works just as well.  There are some off-the-shelf hexaphonic mixers that can be used, or you can try passive mixing, but, IME, it does seem to lose some high frequencies taking that approach.

There are actually tons of different ideas out there.  I tried doing a blade pickup with two coils side-by-side, wired in series, with alternating polarity, and that was probably my personal best result.

IIRC, Qtuners have their coils wound longitudinally, as opposed to transverse, like a normal pickup (rotated 90°).

Elysian TAPs do a cool thing where the "aperture" or diameter of the winding of the coils are different for each string.  Think of it similar to how your iris contracts to let less light in when it's bright outside.  Similarly, by varying the aperture of the inductor, you can focus the electromagnetic field into a tighter space.  It's something I had never really considered as a variable when I first started playing with pickups.

Alumitones use a single "turn" of aluminium to keep the AC impedance extremely low, then use a transformer housed right in the pickup to match the impedance with the amplifier.  It's a super clever idea, but it's something that is also super easy to implement yourself, to see what it sounds like.  It really lowers the noise floor, without using any sort of active electronics.

The only kind of pickup I haven't successfully been able to get at all right is the sustainer pickup.  I've tried so many approaches that I can't keep track of which methods worked the least poorly, but nothing I tried ever did anything like a real sustainer does, right off the shelf.  But it's another nifty concept, and maybe you can play with that as well if you like.  The basic idea is that one coil is a normal pickup, and then another coil has no magnet.  You wire the normal coil to the input of an amplifier (I tried LM386 - a more high-fi amplifier chip should work better in theory), and then wire the output to the magnetless coil to drive the strings into a feedback loop.  I'm not entirely certain, but I believe everything is low-passed so that the system doesn't just squeal endlessly, but instead drives either the fundamental or first or second overtone or a combination of those to keep the string vibrating as long as the player holds the fret down.