Good morning, MEF! Inductance questions.

[Bobbytouche]

Cheers, everybody! New to the forum.

I’ve been winding for about a year. Started working for a high volume manufacturer on Tanac CNC machines. Didn’t learn a whole lot other than how to load the bobbins, select the program, and then assemble the pickups. It was a great experience.

since leaving there l, I’ve decided to toy around with winding at home and goodness there’s a lot to learn! I got myself a Mojotone winder and have wound a couple dozen pickups successfully. But with little to no regard for inductance.

Now that I’ve upgraded (a bit) to a UKCNC mini winder, I’m learning about programming parameters and using the magnetic tensioner, adjusting that as well. But I’m stuck and wasting material.

I’m trying to wind something in the JB realm. Using that as a platform to learn about the effects of different parameters.

Currently, this is my recipe and results
53mm bobbins
6500 turns of 44 AWG enameled copper
17g of tension
120 tpl (which my cnc program determined for me)
A5 smooth magnet
nickel-silver baseplate
plastic spacers
30 AWG start and finish wire
8.7k per coil
5.68H assembled

That inductance is way too low. It should be reading 8H+..

what can I do to remedy this? If my research is correct, tight, linear winding should have done the trick. Maybe I need to raise my tension? I don’t know… I’m at a loss. Lol.

[Helmholtz]

For a given PU design inductance mainly depends on turns number. As inductance increases with turns squared, increasing turns by 20% roughly increases L by 40%.

Compared to turns number the influence of other coil parameters is relatively small.

[Bobbytouche]

For a given PU design inductance mainly depends on turns number. As inductance increases with turns squared, increasing turns by 20% roughly increases L by 40%.

Compared to turns number the influence of other coil parameters is relatively small.

I both understand and don’t understand at the same time (but that’s pretty common for me lol).

I certainly could add turns to reach my goal L. But the general consensus on number of turns on a JB is 6500 per coil. Of course, it wouldn’t be outside realm of possibilty that that internet could be wrong.

Edit: Oh, I remembered incorrectly. A JB is 6,800 turns.

[Bobbytouche]

Update: Wound another bobbin. I did increase the tension a bit to about 20g and increased the turn count to 6800, which should be correct. Moving the right AND wrong direction. This obviously increased the DCR to 9.4. Together, that’ll make an 18.8k pickup. A decent amount more than I’m aiming for. But it also increased the inductance (obviously). The single coil is measuring 3.85H so that going the right direction.

So this brings me back to the same question. How can I keep my turn count where I want it, but bring the L up?

[Helmholtz]

Inductance increases with coil width. Increasing tension tends to lower coil width.

[big_teee]

So what do they sound like, or is L measurements strictly the goal?
Have you tried a full coil of 43.
I make a 43 with A2s that meets my needs.
GL,
T
Also if you are shooting for JB specs, which is on a 49.2mm coil.
Using a 53mm bobbin will read more dcr with same turns.
Mic your wire size, go by turns.
You have a lot of space left on your bobbins, I suspect your 44 is smaller than the old wire specs.
GL,

[Helmholtz]

Good points above.

[Bobbytouche]

So what do they sound like, or is L measurements strictly the goal?
Have you tried a full coil of 43.
I make a 43 with A2s that meets my needs.
GL,
T
Also if you are shooting for JB specs, which is on a 49.2mm coil.
Using a 53mm bobbin will read more dcr with same turns.
Mic your wire size, go by turns.
You have a lot of space left on your bobbins, I suspect your 44 is smaller than the old wire specs.
GL,

There’s a certain amount of boom that comes out my JB. The EQ balance puts a smile on my face. That coupled with the type crunch is just overall very nice. I’m not great with the adjectives, but that pretty well sums it up. My first couple attempts with much lower L resulted in a complete lack of low end by comparison. I’m still waiting to pot this one I did today, but I got 8.15H. The 6800 turns I put on there resulted in 9k per coil. My fear in raising the DCR that much is muddiness.

and you’re correct. Still a good amount of space left on the coil. I had read that SD may have used a wire with a smaller core and thicker insulation. Or perhaps it was proper 44 AWG but thicker insulation resembling an outside diameter of something like a 42.5.

[Bobbytouche]

Ya know… thinking back to the company I used to wind for (again, I merely ran the machines and assembled pickups. I learned nothing of value there. Lol.) I do remember our coils being relatively spongy to the touch. Not loose. But also not rock hard like mine since I’ve cranked up the tension to 20g. That doesn’t solve the inductance question, but may lend some insight the absence of bass in my recent attempts.

so that brings me here…
looser coil = wider coil = fatter sound… but also = lower induntance.

tighter coil = thinner coil = more trebly sound but also = higher inductance.

sort of contradicts itself as higher inductance will add low end, no?

[Bobbytouche]

Update! Again. This last one came out pretty good! 18k and a 7.5H tested at the jack. It does seem to lack some high end this time. I think easing back on the turn count just a hair and taking it easy on the tension will put it right where my ears will like it. Still not quite understanding how Seymour and the heavy hitters (and you guys) are getting higher L with lower turn counts. But I figure I’ll catch on as I go.

[Helmholtz]

looser coil = wider coil = fatter sound… but also = lower induntance.

As said above, a looser, wider coil may slightly increase - but not lower inductance.
Apart from that I can't think of a reason why it should give a fatter sound (without increasing turns count) - and I've never seen or heard a proof to that theory.

tighter coil = thinner coil = more trebly sound but also = higher inductance.

A tighter wound coil will neither increase inductance nor treble.

sort of contradicts itself as higher inductance will add low end, no?

Higher inductance attenuates treble and typically adds mids, so the sound will be darker or fatter.

There's no direct way to increase real bass response. All typical magnetic PUs measure flat from just above 0Hz to at least a few hundred Hz.
Of course, less treble and more mids might give the illusion of more low end.

[bbsailor]

Update! Again. This last one came out pretty good! 18k and a 7.5H tested at the jack. It does seem to lack some high end this time. I think easing back on the turn count just a hair and taking it easy on the tension will put it right where my ears will like it. Still not quite understanding how Seymour and the heavy hitters (and you guys) are getting higher L with lower turn counts. But I figure I’ll catch on as I go.

Use a volume pot value that is near 40 times the DC resistance of the pickup to have optimal loading and maintain the full bandwidth of the pickup. Try to limit your guitar cable coax length to 10 ft as this cable adds about 30 pf per foot of length that cuts down on higher frequencies.

The human ear is most sensitive to frequencies in about the 1KHz to 4KHz range so if your pickup has a resonance in this range, keep this in mind. Look up the Fletcher Munson Curve to see the graph of this.

Keep winding, testing, measuring and comparing sounds as a very good way to learn. Just get a good understanding about the optimum loading of your various designs.

Joseph J. Rogowski

[Antigua]

Update! Again. This last one came out pretty good! 18k and a 7.5H tested at the jack. It does seem to lack some high end this time. I think easing back on the turn count just a hair and taking it easy on the tension will put it right where my ears will like it. Still not quite understanding how Seymour and the heavy hitters (and you guys) are getting higher L with lower turn counts. But I figure I’ll catch on as I go.

Are the slugs and screws in the bobbins when you measure the inductance? The slugs and screws will increase the inductance.