The Misleading Nature of DC Resistance in Regard to Pickup Coils

[cooljuk]

We as musicians often see DCR listed as the only, or one of few, specifications given for a guitar pickup. This is something of a bad habit of the guitar and pickup industry that has lead to a bad habit of relying on that figure by musicians.

I'd like to throw out some examples to help clarify the significance, or lack of significance, of DCR in a guitar pickup. These are real actual measured results from coils I've wound, I'm not speculating for the sake of an example.


Coil A:
Wire Used: Plain Enamel @ 1.7180 Ohms/ft
Turns: 6000
DCR: 4.36k Ohms
Inductance: 1271.1 mH @ 120 Hz / 1504.6 mH @ 1kHz

Coil B:
Wire Used: Plain Enamel @ 1.5767 Ohms/ft
Turns: 6000
DCR: 4.16k Ohms
Inductance: 1306.1 mH @ 120 Hz / 1310.1 mH @ 1kHz

Coils A and B have the exact same turn count, both are wound with what would be considered AWG 42 wire. The DCR is quite different, but the sound is nearly the same. A humbucker made of two A coils would have a DCR of 8.72k Ohms. A humbucker made of two B coils would have a DCR of 8.32k Ohms, but these two humbuckers would sound just about the same as each other.


Let's look at another pair made with the exact same wire spools:

Coil C:
Wire Used: Plain Enamel @ 1.5767 Ohms/ft
Turns: 5300
DCR: 3.49k Ohms
Inductance: 996.7 mH @ 120 Hz / 970.6 mH @ 1kHz

Coil D:
Wire Used: Plain Enamel @ 1.7180 Ohms/ft
Turns: 4800
DCR: 3.49k Ohms
Inductance: 827.3 mH @ 120 Hz / 826.7 mH @ 1kHz

With coils C and D you will see that the DCR is exactly the same! ...but look at the rest of the figures. The turn counts, and accordingly the sound, are VERY different! 500 turns per coil difference is significant.


Now take into consideration that these are individual coils of a humbucker. When you add the two coils in series (like a humbucker typically does) you will double the DCR, and the DCR differences. In the example of coils C and D, if you made a humbucker with two C coils it would read 6.98k total DCR and have a total of 10,600 turns. If you made a humbucker with two D coils it would also read 6.98k total DCR but have a total of only 9,600 turns. Two pickups, both wound with AWG 42 wire with exactly identical DCR and 1000 turns wire of difference. They will sound VERY different but your multimeter or a manufacturer's stated specs won't give you even a clue to that difference.

Want to talk about magnets under all these coils? That changes the sound even more, without changing DCR one bit. Can you imagine how the two humbuckers made from coils C and D would sound if one had an A2 and another had an A5? The DCR wouldn't account for any differences in these two VERY VERY different sounding humbuckers. This is scraping the tip of the iceberg. Steel alloys, mass and shape of pole pieces, coil patterns and shape, turns per layer, wire tension, wire type, insulation thickness, charge level of magnets, magnets of the same type and charge from different foundries and lots - all of these are just some examples of variables that significantly alter the sound of a guitar pickup, but do change a pickups DC resistance.

I'm not claiming to be the authority on the subject or that this post is all encompassing by any means whatsoever. What I do hope it will do is simplify, in a few easy examples, why DCR should not be considered definitive of a pickup's voicing to anyone who can grasp some basic figures and concepts. The guitar and pickup industry has used DCR as a crutch for decades and misinformed the public in doing so. The reason for this is not malicious, but because there is no one figure, or even set of figures, that will define a pickup's voice absolutely. I hope this helps open some minds as to how things really work.

 

[Oranjeaap]

The DCR is a measurement of resistance. It depends on wire material, diameter, length.

It's that and only that. Not a measure of output. I hate when people say: output 8.0. Thats wrong on so many levels

The DCR can give an idea about the output yes, that's all.

 

[Zhangliqun]

In your second example, how is the DCR the same? Does the one with fewer turns have higher tension so the wire is stretched a little?

 

[Oranjeaap]

Put in a bigger/stronger magnet. BOOM, more output. DCR stays the same.
Put in ceramic magnet. boom different tones same DCR

 

[cooljuk]

In your second example, how is the DCR the same? Does the one with fewer turns have higher tension so the wire is stretched a little?

No the tension is exactly the same. Though all examples above are the same gauge of wire, the range of tolerance within the NEMA specification for magnet wire allows for different copper core thicknesses within that gauge. See in red below to note the difference in Ohms per foot of wire. This is what accounts for the difference in DCR.

Coil C:
Wire Used: Plain Enamel @ 1.5767 Ohms/ft
Turns: 5300
DCR: 3.49k Ohms
Inductance: 996.7 mH @ 120 Hz / 970.6 mH @ 1kHz

Coil D:
Wire Used: Plain Enamel @ 1.7180 Ohms/ft
Turns: 4800
DCR: 3.49k Ohms
Inductance: 827.3 mH @ 120 Hz / 826.7 mH @ 1kHz


I believe in the 1950's the tolerance for a given gauge of magnet wire was four times looser than it is today, as today's wire standards are split into not only half gauges but also minimum-to-nominal and nominal-to-minimal within the half gauges, making guesswork about pickups based on DCR alone four times less accurate for vintage pickups. The above examples are all modern wire, to be clear.

Here's a link to the (present day) NEMA Standard Charts.
In Imperial: http://www.elektrisola.com/enamelled-wire/technical-data-by-size/nema-mw1000c.html
In Metric: http://www.elektrisola.com/enamelled-wire/technical-data-by-size/nema-mw1000c-metric.html

 

[CheopisIV]

I have a ~4k Neck bucker and a ~4.8k Bridge bucker that are significantly higher output than the 20k bucker I wound a few years back Very non-conventional in construction and currently just trying to settle on a name.

It's fun to play with these things and goes to show how much more is going on than the DC of a pickup.

 

[Zhangliqun]

So you're talking about diameter variations within the manufacturer's tolerance on a single spool then. Yes, that can happen. Although the wire vendor I use seems to be extremely consistent regarding DCR to turn count ratio, assuming more or less the same ambient temp at the time of each reading, of course.

 

[Mark V Guitars]

So you're talking about diameter variations within the manufacturer's tolerance on a single spool then. Yes, that can happen. Although the wire vendor I use seems to be extremely consistent regarding DCR to turn count ratio, assuming more or less the same ambient temp at the time of each reading, of course.

This is precisely why finding some of that old wire laying around in some storage facility can be such a barn find. Back in the 50's, there were bigger variations in the wire, and as a result, we see some pickups that just seem to have been made from unicorn shin bones and pixie dust. The problem with super tight consistency today, is that you can't just order wire with a particular tolerance variation. Believe me, I've tried. Well, that and most people don't want to go test hundreds of spools of wire.

 

[WolfeMacleod]

The problem with super tight consistency today, is that you can't just order wire with a particular tolerance variation. Believe me, I've tried. Well, that and most people don't want to go test hundreds of spools of wire.

Oh, you certainly can order wire that has wide variance. It's called Min-Max.
Ther'es also Min-Nom (which most people use) and Nom-Max.

Good stuff. People need to realize that DCR doesn't mean much. I had to explain it to someone just today.

 

[cooljuk]

So you're talking about diameter variations within the manufacturer's tolerance on a single spool then.

Not within the same spool necessarily, though that could also happen. Probably more with older wire. I find modern wire spools to be very specific. When I say variance in tolerance, I mean the NEMA standard for how thick a specific gauge of wire is supposed to be. With 10 different spools of 42 AWG PE magnet wire from the same manufacturer, even the same batch, they can have 10 different Ohms per foot readings. All labeled exactly the same, all the same part number, but all with slightly different resistive properties that really add up over the course of a mile of wire on a pickup.




You can have two coils, both wound with the same official gauge of wire, with different turn counts, and with the same DCR. They will sound very different.

...and also...

You can have two coils, both wound with the same official gauge of wire, with the same turn counts, and with very different DCR. They will sound very similar.

 

[Zentar]

I bought a used set of Gibby humbuckers that were unmarked. I was able t0 ID them by their DCR.
DCR is a big help selecting P90s if you want a 50-60s tone.
I find DCR to be a great help picking some pickups but not others. It's just one indicator though.

 

[cooljuk]

The problem with super tight consistency today, is that you can't just order wire with a particular tolerance variation. Believe me, I've tried.

Try harder. Can and do, here.

 

[ThroBak]

Ohms per foot is one of those details you have to pay attention to. I have wire samples with ohms per foot measurements from the vintage repairs and rewinds I do. I also mic every spool and measure the ohms per foot for each spool. I sort the wire this way then assign it to specific winding stations on my Leesona 102 and the rest of the ThroBak winding machines. This allows me to make a variety of PAF models with the ohms per foot and diameter tolerance as part of the spec.. Essentially you control a random variable in vintage pickups and build the "random" variable into the pickups specs. a way that allows it to be repeatable. This is one reason it is important to wind from multiple spools of wire for a pickup like a PAF if you trying to make a repro. I have been sorting wire like this for years. Ohms per foot and diameter within 42AWG tolerance affects attack and overall tone, bite and openness of a pickup.

 

[morbidalex666]

I have a ~4k Neck bucker and a ~4.8k Bridge bucker that are significantly higher output than the 20k bucker I wound a few years back Very non-conventional in construction and currently just trying to settle on a name.

It's fun to play with these things and goes to show how much more is going on than the DC of a pickup.

OK, how about a pic then?!

 

[DADGAD]

To us laymen, the DC is only a guide and starting point on what to expect. It's like looking at a dating profile and seeing that a woman is "blonde". You won't know more about the personality unless it is described to you or you experience it in person.

 

[CheopisIV]

OK, how about a pic then?!

Erm, okay.. the bridge pup is the ~5k screamer. Looks just like any other bucker but the internals are where the tricks are taking place.

 

[darthphineas]

Been preaching about the "illusion" of focusing on DCR for quite some time.

I appreciate when builders throw out specs that go beyond DCR. For a random example, I'll refer to DiMarzio, who has been including output readings for years. That means I can see a lower DCR and a higher output or a higher DCR and a lower output (along with other posted specs, such as magnet type) and have a much better idea of the tone.

Getting a LCR meter has been a big help in understanding pickups even more. I've been starting to include inductance readings in my reviews, as I know more people are used to seeing henries than capacitance readings. It's very cool to see nF specs in the readings from the sample pickups in the OP.

 

[Zhangliqun]

Partial disagreement here. DCR gives you some idea how much wire is in the coils, if you know how to control for different wire gauges, and that's not nothing. The total length of wire will certainly affect the sound. Doesn't mean much between two pickups otherwise identical but one 8.0k and the other 8.3k. But to say DCR would tell you nothing about two otherwise identical pickups, one 7.0k and the other 9.5k (especially a neck bucker or neck P90), is just as amateurish as saying it's the be-all/end-all spec.

 

[cooljuk]

Zhang - the only time the word "nothing" appears on this page is in your post. I don't think anyone said DCR tells nothing about the pickup. I don't mean to sound confrontational, but what exactly are you disagreeing with? I just don't understand.



In the example below - what can you say about the different sound of these two coils, based only on DCR? They are both wound with AWG42 PE wire.


Coil C:
Wire Used: Plain Enamel @ 1.5767 Ohms/ft
Turns: 5300
DCR: 3.49k Ohms
Inductance: 996.7 mH @ 120 Hz / 970.6 mH @ 1kHz

Coil D:
Wire Used: Plain Enamel @ 1.7180 Ohms/ft
Turns: 4800
DCR: 3.49k Ohms
Inductance: 827.3 mH @ 120 Hz / 826.7 mH @ 1kHz


A humbucker built with 2 "C" coils and a humbucker built with two "D" coils would have the same DCR, but have a 1000 turn count difference and absolutely sound different because of that (10600 total turns for "C" humbucker versus 9600 total turns for "D" humbucker)

 

[Tweaker]

I realize this is about DC resistance, but I have a question for the winders that kind of relates to DC resistance. I've never quite understood why you use such tiny gauge wire for the winding! Do you use the tiny gauge because you can get more winds and have more control over the DC resistance/pickup output?

What would happen if, hypothetically speaking, you were to strip a really long length of say, 24 gauge stranded wire, and used all those strands at once to wind a pickup? (Essentially winding 24 gauge wire without the insulation, for lack of a better description)