Compiled Pickup Data (Various Brands)

[Antigua]

The document is titled "Pickup Specifications", technically these are measurements. The specification is what the manufacturer intended, but what is in hand might (probably) vary from the specification. For example, the document says a particular Stratocaster pickup in 1962 had 8220 turns, but it's very not likely that Fender spec'd that turn count for that year.

Also I see them referred to as "hand wound", that's modern parlance in the market place, but technically they're hand guided and/or hand tensioned. I think only a few pickups in existence were actually wound by hand, one turn at a time.

For the purpose of recreating pickups, it would be arduous to collect turn counts of pickups, because it requires dismantling them and it's a lot of work, but with a $100 LCR meter you can record inductances without having to take them apart at all, and from that you would only have to determine how many turns it takes to arrive at that inductance, and upon doing so, you would have created a pickup that electronically performs like the target pickup. The turn count alone can be misleading if other factors affecting inductance aren't account for. For example, Wilde Pickups is offering an AlNiCo version of their microcoil, but it appears that they retained the same turn count, but because the AlNiCo has a lower permeability than the steel screws of the original, the inductance is a lot lower and it sounds a lot brighter, and that might not have been the intended outcome.

[jtb]

For the purpose of recreating pickups, it would be arduous to collect turn counts of pickups, because it requires dismantling them and it's a lot of work, but with a $100 LCR meter you can record inductances without having to take them apart at all, and from that you would only have to determine how many turns it takes to arrive at that inductance, and upon doing so, you would have created a pickup that electronically performs like the target pickup.

I'm pretty new to reverse engineering the things - is there a guide or calculator that can help determine turns from inductance measurements? I found a bunch of resistance ratings per meter for various wires, but it didn't help me too much.

[Antigua]

I'm pretty new to reverse engineering the things - is there a guide or calculator that can help determine turns from inductance measurements? I found a bunch of resistance ratings per meter for various wires, but it didn't help me too much.

I'm seeing a DE-5000 on Amazon for only $80 right now https://www.amazon.com/Labs-DE-5000-...qid=1578428155 , the cheapest Ive ever seen it go for. When set to inductance series mode (Ls) at 100Hz, it gives good inductance values for guitar pickups, even ones with a lot of steel parts and excessive eddy currents. When set to capacitance parallel (Cp) at 100kHz it gives very good capacitance values as well. I've measured a lot of capacitances from inductance and resonant peak measurements, and found that the DE-5000's measurements are almost always right on the money. The DE-5000 also measured DCR as it's final mode, which unlike the Extech meter, saves you from having to use a separate ohm meter to get that value.

Note that pickups with a foot of shielded hookup wire will read an extra 40pF to 80pF capacitance due to the presence of shielding, you would have to disconnect the hookup wire in order to get a true capacitance measure. The capacitance is not a highly important figure, so it might not be worth the trouble of removing it. Alternatively you can measure the length of the hookup cable and just make note of it so that it can be accounted for along with the measured capacitance. Fender style pickups with distinct lead wires add no capacitance (<1pF) so long as the wires are not touching together. The inductance is much, much larger than the capacitance, relatively, but if you're trying to recreate a pickup, and the target happens to have a very high or very low capacitance, you might get better accuracy by taking it into account. For example, most Strat pickups measure around 100pF, but you might be tasked with recreating one that happens to measure over 200pF, or you would want to make sure yours dont read over 200pF if the target is closer to 100pF.

As for determining the turns, there's no good way to do that either with DCR or inductance, because with several thousand turns on a coil, there is a lot of room for drift and non-ideal factors. The only way to do get the turn count is to unwind and rewind it, counting how many turns it completes when it reaches the end of the wire. I know some people measure DC resistance as they're winding the pickup, they'll stop and check the DC resistance, and then keep winding until they reach a certain mark, I'd think the same could be done with inductance, except that any steel pole pieces would have to be present in the bobbin. An inductance measurement of a coil without its steel slugs or screws would be invalid. The inductance metric will be more accurate than the DC resistance, because the inductance doesn't care what the wire gauge is, where as the DC resistance is be heavily dependent on it.

[Helmholtz]

help determine turns from inductance measurements

It may help to know that inductance increases with the number of turns squared. So 10% more turns roughly produce 20% higher inductance, everything else being unchanged.

[big_teee]

Alright so there's a lot of stuff I have to start cataloguing in this thread - which is perfect! Thanks!

Not to mention I found a few more spreadsheet pages on my computer with more data, and then links to manufacturer data repositories...this might take a while..

But any ideas or other stuff to contribute will still be appreciated - I'll post again once I've got it all sorted out for a second review.

jtb, I would continue on with you data gathering and spreadsheet, and not get sidetracked with the LCR data.
GL,
T

[jtb]

jtb, I would continue on with you data gathering and spreadsheet, and not get sidetracked with the LCR data.
GL,
T

Don't worry, I still intend on that - I figure I'll just get it all in place and then decide what's helpful and what's not. The info I've gotten about inductance/winds is pretty much where I was at before: wishing I had some formal electrical engineering training. Maybe someone can just tell me if this thinking is correct:

[pickup inductance] / [wire gauge & material resistance per meter] = [length of wire on the bobbin]

which would then allow the number of winds to be calculated with a formula to account for the increasing distance per wind as the coil grows?

If there's a formula for all this, I'd like to make a nice little calculator script for it.

[Helmholtz]

[pickup inductance] / [wire gauge & material resistance per meter] = [length of wire on the bobbin]

No, inductance depends on all coil dimensions as well as core type and nearby conductive or ferromagnetic parts - and of course on the number of turns squared.

[Antigua]

Don't worry, I still intend on that - I figure I'll just get it all in place and then decide what's helpful and what's not. The info I've gotten about inductance/winds is pretty much where I was at before: wishing I had some formal electrical engineering training. Maybe someone can just tell me if this thinking is correct:

[pickup inductance] / [wire gauge & material resistance per meter] = [length of wire on the bobbin]

which would then allow the number of winds to be calculated with a formula to account for the increasing distance per wind as the coil grows?

If there's a formula for all this, I'd like to make a nice little calculator script for it.

There's not really any way to calculate turn counts to a precision that is better than +/- 100. If you wanted a high precision data set, you would have to unwind a lot of pickup and count the turns. Ideally that would be great, because suppose you want to clone a pickup, even if you could match the inductance, duplicating the turn count just seems more impressive. But how can you get all those turn counts? The only way I know of, is the manufacturer disclosing the info, which most will not, or dismantling a lot of pickups. That would cost a lot of time and money. If you repair pickups, you could gather than info as you repair pickups one at a time, and it seems that this is how Seymour Duncan acquired data about various Stratocaster pickups in the Fender portion of your database. But if you wanted to grow the database more quickly, you would have to buy an example of each, since you probably can't dismantle a pickup you don't own.

If instead you don't plan to gather the data directly, but just gather from outside sources, you ought to put where the data came from. For example, the PRS data appears to have come from a spec sheet that dates back to 1995 http://u.cubeupload.com/Border_Collie/IMG0966.jpg , noting the original source is important for establishing veracity, and or how up to date it is.

Another resource that would be helpful, is as you mentioned, it's difficult to correlate either inductance or DC resistance with turn counts. On the bright side, there is only a small handful of pickup form factors that are very common, Strat and Tele bobbins with A2 or A5 pole pieces, PAF type with screws and slugs, P-90's, Filter'trons and some base guitar pickups. After that they become less common. You could take a generic Strat bobbin with ALNiCo 5 pole pieces, wind on 500 turns of 42 AWG, measure the DC resistance and the inductance, and then write it down, add another 500 turns, measure it again, and in the end create a table that allows you to guess approximately how many turns on 42AWG on an AlNiCo 5 Strat bobbin it takes to reach a target DC resistance or inductance. Then if you know the target inductance or DC resistance, you can refer to that table to approximate how many turns it would take to get to that target measurement, cutting down on the amount of trial and error.

[jtb]

No, inductance depends on all coil dimensions as well as core type and nearby conductive or ferromagnetic parts - and of course on the number of turns squared.

That was dumb of me not to be considering the whole :|

Is there already a complete formula for this in existence? That's what I'm really looking for I think, it'd help me come up with some better questions at the very least. I'm gonna go google around a bit.

Another resource that would be helpful, is as you mentioned, it's difficult to correlate either inductance or DC resistance with turn counts. On the bright side, there is only a small handful of pickup form factors that are very common, Strat and Tele bobbins with A2 or A5 pole pieces, PAF type with screws and slugs, P-90's, Filter'trons and some base guitar pickups. After that they become less common. You could take a generic Strat bobbin with ALNiCo 5 pole pieces, wind on 500 turns of 42 AWG, measure the DC resistance and the inductance, and then write it down, add another 500 turns, measure it again, and in the end create a table that allows you to guess approximately how many turns on 42AWG on an AlNiCo 5 Strat bobbin it takes to reach a target DC resistance or inductance. Then if you know the target inductance or DC resistance, you can refer to that table to approximate how many turns it would take to get to that target measurement, cutting down on the amount of trial and error.

I was hoping workable data would already be in existence with some known material qualities, like the magnet types/strengths, wire gauges and metals, insulation types, etc. I wrote this down about 6 months ago in a spreadsheet, but I never included any context for it so I'm not sure how I intended to use it - I know I wanted it to make a calculator though:



I've got a migraine now so I can't do much thinking anymore tonight, but I'll just paste something here and maybe you can tell me if you think it'd be accurate enough to make comfortable inferences from: http://www.jdguitarworks.com/coil/coil.html

[Helmholtz]

Is there already a complete formula for this in existence?

I completely understand what you are looking for. But unfortunately there is no such comprehensive formula. There are just too many complex interdependencies between parts and dimensions.

In his book "Physics of the Electric Guitar" Prof. Manfred Zollner presents a lengthy and complicated formula (depending on length, width, height and thickness of the coil as well as turns number squared) that allows to calculate the inductance of an isolated PU coil (without any metal parts) to good accuracy. But as soon as you add polepieces and/or other metal parts, the inductance changes considerably. E.g. the inductance for a Strat PU calculated from the formula increases by around 30% when inserting A5 poles. Other pole materials and pole dimensions have different effects. Even the pole charge may matters (a little).

The formula only works if the final coil dimensions are known to good accuracy.

Wire resistance has no influence on inductance.

[jtb]

Wire resistance has no influence on inductance.

Someone posted a picture of PRS's pickup data above and there's a column labeled "resistance", which shows 15k, 11k, 8.8k, etc for the coils.

I'm just wondering why and when one would measure resistance or inductance, what each measurement's purpose is in pickup making. Sorry for this super noob question that's totally off-topic here, but this seems to have turned into my crash course in pickup deconstruction.

[Helmholtz]

I'm just wondering why and when one would measure resistance or inductance, what each measurement's purpose is in pickup making.

Resistance is just an unavoidable side effect of any conductor. The longer and thinner the wire the higher its resistance. But PUs would work just fine if resistance were zero.
OTOH, inductance is an electromagnetic coil property that mainly determines a PU's frequency response together with the cable capacitance. Together they produce a resonant peak and determine the bandwidth.

A PU's output increases with the turns number.

So if you know inductance and the turns number, there is no need to care about resistance.

[Antigua]

Someone posted a picture of PRS's pickup data above and there's a column labeled "resistance", which shows 15k, 11k, 8.8k, etc for the coils.

I'm just wondering why and when one would measure resistance or inductance, what each measurement's purpose is in pickup making. Sorry for this super noob question that's totally off-topic here, but this seems to have turned into my crash course in pickup deconstruction.

If you know the DC resistance and the wire gauge, you can rough guess the turn count based on the resistance per foot of 42AWG and a knowledge of how many feet of wire it takes to achieve so many turns, but for various reasons it would never be too accurate, because DC resistance changes with temperature, and wire can stretch, becoming thinner than its nominal thickness, as it's wound onto the bobbin, resulting in a higher DC resistance for a given number of turns.

The inductance really tells you if you reached an objective or not. For example, if I have a Strat pickup that is 2.65 henries, and I want a copy of that pickup, the real test of whether the copy is precise is whether or not the duplicate is also 2.65 henries. It could have the same DC resistance, and even the same number of turns, but if its not 2.65 henries, the copy liable to sound a little different, because it will have a different resonant peak. If the turn count is the same, there are good odds that the inductance will also be very close, but the two values can still drift somewhat.

[David King]

If you're mass producing a particular pickup and want consistency then measuring inductance is a quick way to check for defects in the wind. Say there is an internal short in the coil where insulation got rubbed off and a few hundred turns disappeared. You wouldn't see that necessarily with a DCR test but you might hear it and presumably an induction test will show it.

[bassjase128]

you really should see a few hundred turns missing with a DCR test especially if it open circuits!