The Misleading Nature of DC Resistance in Regard to Pickup Coils

DADGAD

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Lots of nerdy tech stuff being discussed that is too much for my poor brain to comprehend.
 

CheopisIV

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Does it have a neo in it?!

Several actually ;) and a Ceramic bar and some off the wall wire I was told had no business in a pickup. I chose to try it anyway and couldn't be happier. Of course it took 3 different configs and a destroyed bobbin to make it sound good so not an instant win.
 

dmoss74

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There are some more advanced measuring systems that try to take into account the magnets and ferrous components of a pickup, but they are still only measuring frequency response, not taking into account dynamics/feel, and are not including the strings/guitar/amp/player which are all very important. This is probably why these "breakthroughs" didn't really go anywhere and become an industry standard. I'm fascinated by this aspect of research though, and would love to explore more in that area.

i'm surprised there is no graph type of measurement for guitar pickups, but realize how daunting that could be. because--like mentioned--there are myriad post pickup variables that influence how a pickup will sound.

but you pickup guys have to take some responsibility in this as well.

now, don't get all defensive....

what i mean is, in lieu of being able to give any definitive tonal identifiers, a lot is left to "sounds like player a" stuff, or terms like that. some schmo (like me) might want to get a sound like one of my guitar heroes (i actually don't, i am just using this as a reference), and then when i get a pickup that was described as "so and so's sound", it sounds nothing like so and so's sound, due to my particular post pickup gear.

in my anecdotal findings, i can use dcr, in conjunction with magnets, wire, coil offset, etc to get me something that closely resembles what i'm looking for. but the pickups are only a part of the equation. the amp(s) are even more important. i can't expect to sound like junior brown, if i'm playing through a jcm 800. no pickup is going to do that for me. :)
 

CheopisIV

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i'm surprised there is no graph type of measurement for guitar pickups, but realize how daunting that could be. because--like mentioned--there are myriad post pickup variables that influence how a pickup will sound.

but you pickup guys have to take some responsibility in this as well.

now, don't get all defensive....

what i mean is, in lieu of being able to give any definitive tonal identifiers, a lot is left to "sounds like player a" stuff, or terms like that. some schmo (like me) might want to get a sound like one of my guitar heroes (i actually don't, i am just using this as a reference), and then when i get a pickup that was described as "so and so's sound", it sounds nothing like so and so's sound, due to my particular post pickup gear.

in my anecdotal findings, i can use dcr, in conjunction with magnets, wire, coil offset, etc to get me something that closely resembles what i'm looking for. but the pickups are only a part of the equation. the amp(s) are even more important. i can't expect to sound like junior brown, if i'm playing through a jcm 800. no pickup is going to do that for me. :)

You mean like this? I was comparing resonant frequency of a Tele neck VS Tele bridge.
TeleSetComp.jpg


I think it's cool and informative, but the biggest problem with this type thing is there's no standardized method for measuring pickups and no standardized tools. We'd all need to get onboard to make a universal set of techniques for analysis. So why doesn't that happen? It would greatly interfere with marketing hype and the mythos that's been cultivated through years of misdirection by a lot of guys who sling copper ;)

Generalized specs that are actually floating data (DC, wire type, magnet type, metals) are easy to measure with simple devices and really tell jacksh*t about the pickups so preserve the hard data that all winders keep as proprietary.
 

dmoss74

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You mean like this? I was comparing resonant frequency of a Tele neck VS Tele bridge.
TeleSetComp.jpg


I think it's cool and informative, but the biggest problem with this type thing is there's no standardized method for measuring pickups and no standardized tools. We'd all need to get onboard to make a universal set of techniques for analysis. So why doesn't that happen? It would greatly interfere with marketing hype and the mythos that's been cultivated through years of misdirection by a lot of guys who sling copper ;)

Generalized specs that are actually floating data (DC, wire type, magnet type, metals) are easy to measure with simple devices and really tell jacksh*t about the pickups so preserve the hard data that all winders keep as proprietary.

i like that you did that. very cool. and in the same vein, you can read microphone graphs all day, but until you plug them into a mic pre, they are just frequency guides. but i didn't know that pickups could graph the same way.

kudos! that's a good starting point. now graph how different formulated magnets (and two or three strength levels each) would alter that graph. then add in wire gauge, and coil strengths. :)

i keed. :)

when the ore goes to slag, this is inherently a "dog chasing his own tail" thing, regarding pickups. there are just too many variables. but certain things can be empirically arrived at. lower winds will (should) tend to be a little brighter (higher resonant peak) than higher winds. things like that. but the variables are almost insurmountable to arrive at conclusions.

somebody needs to dig up faraday, beat the crap out of his bones, and then re intern them. :)
 

cooljuk

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I'm all about coming up with a standard of measurement, but I think there are some brick walls in the physics of it.



If you measured the pickups in that graph above with an inductor coil, you only measured the coils of the pickups, not the entire pickups.



...what I mean is, induction frequency tests "ignore" the magnets and any steel, copper or brass etc. parts of the pickup and only measure how a coils responds to an oscillating electrical current. The result is just the coil responding to electrical induction, acting like the secondary of a transformer. So if you swapped a bunch of different AlNiCo magnets into those pickups, and graphed them all, the graphs would all look basically identical. ...but we know that swapping the magnets would significantly change the real-life sound of the pickups in a guitar.

In fact, if you pull the magnet out of a pickup while playing a source though an induction coil, the output of the pickup will be seemingly identical - with the magnet completely removed from the pickup! :shock: The pickup with the magnet removed would be dead in a guitar, of course.

That missing information is compounded even more with humbuckers where there are additional ferrous parts creating a complex magnetic field, and the magnet itself acts like a steel reflecting plate (unless ceramic). That's all basically ignored by an induction coil frequency analysis, as far as I have observed.




On the other hand, if you measured the pickups in the graph while in a guitar while playing, you induced a bunch of other non-repeatable variables from the guitar and your playing.



I think that's the catch 22, more so than there being a lack of standardized system.

To comprehensively test a guitar pickup in a standardized way, you need to generate an oscillating magnetic field, using the pickups own magnet, and without creating an electrical induction source. You not only need the magnetism without induction, but the actual mechanical interference in the pickup's field, as well. That's the (seemingly) dead-end as far as I can tell. Not that I'm a physicist or anything. ...I actually hope I'm wrong about this. :D

All that said - even if that physics barrier were overcome, this is still only frequency response we are talking about charting and doesn't account for dynamic response or feel or the microphonic/acoustic aspect of a pickup, nor the way a pickup responds to different loads which are all very significant aspects of a pickup's "voice."


Not that that information isn't valuable. I use induction tests on coils plenty and I'm sure there are uses beyond what I do with them. It's just not even remotely close to the comprehensive graphs and charts that represent the sonic response of microphones, speakers, headphones or cartridges. I'd love to be involved in taking it there, though. :thumb:
 

dmoss74

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okay, then there has to be a way of doing a venn diagram, which involves the major components of the circuit: wire, coils, magnet. no? and then factor in the frequency responses, dependent on all those factors.

c'mon, guys. this can't be that hard. :) just kidding. but seriously, there will probably be some way of getting this all down much more intuitively, 50 years after we're all in the dirt.
 

cooljuk

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but seriously, there will probably be some way of getting this all down much more intuitively, 50 years after we're all in the dirt.

Most likely, it will involve a Firebird X and USB. :fingersx:
 

CheopisIV

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The whole subject of tone is the biggest kicker for sure, and it's not JUST pickups when you go that route...now we're talking about the guitar, the compounding electronics of the harness, strings, picking technique and everything between output jack and your ears!

This also includes the room, flooring walls and the pictures hung on them. Worse yet, we add in the human factor which will never be standardized for measurement. No matter what we offer for measurement and data, it will really only ever be relevant to our own products and can't be standardized to suit any meaningful measurement on the most important factor. . "How do they sound? "
 

Zhangliqun

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No question, DCR can be very misleading. Even I agree to that. You have to know how to account for the myriad other factors.

But even if there was this mythical single datapoint that would tell you dead-on what the output and basic tonal character was, it still wouldn't tell you what you REALLY want to know, which is (a) what does the bleepin' thing SOUND like, particularly in my guitar, and (b) how does it feel (ie: how does it react to my touch)? Do I have to labor to the point of arthritis to get that sound or does it come effortlessly?

Even with such a wonder-spec, there would still be only one way to find that out, which is to take the leap and spring for the pickup and then turn around and sell it at a loss when it doesn't work out -- an annoying cycle that got me into winding...
 

Zhangliqun

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Does this mean you'll buy pickups from me now? (I couldn't resist...)
 

freefrog

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...what I mean is, induction frequency tests "ignore" the magnets and any steel, copper or brass etc. parts of the pickup and only measure how a coils responds to an oscillating electrical current. The result is just the coil responding to electrical induction, acting like the secondary of a transformer. So if you swapped a bunch of different AlNiCo magnets into those pickups, and graphed them all, the graphs would all look basically identical. ...but we know that swapping the magnets would significantly change the real-life sound of the pickups in a guitar.

That's what I've noticed as well in my experiments... but not totally.:)

As alnico grades change the inductance, the resonant peak(s) of the pickup are not precisely identical.

If I find enough free time to search, I'll try to post a chart showing the resonant peaks obtained from the same pickup with various alnico bars: there's a slight difference (I lack of time right now, my archives being crowded with hundreds of frequency charts about pickups).

NOTES

1-FWIW, I think that frequency charts can be meaningful about the whole pickup if we measure other things than the resonant peak: THD and dynamic range, for example, are different and meaningful (IME/IMHO) when measured with the same coil(s) and different mag(s).

2-FWIW too, I've developped a routine to test pickups, that I use since 2003 and that I find efficient: I play each pickup direct to the board through the same cable. A first track records single notes from unfretted low E to the highest note available on the guitar. A second track records fretted atonal chords from unfretted strings to 12th fret. Then a frequency analyser set on "infinite" stacks the frequency produced. I do my best to have a consistent playing but I can tell you that even with the most inconsisten attack, I always end with similar looking spectra for a same pickup. :)

3-Oh, and I find INDUCTANCE 10 times more meaningful than DCR - even if inductance is proportional to resistance, all other things being equal, there's HUGE difference of "inductivity" between PU's of the same DCR, according to their design and actual physical structure.

4-Last but not least: when I test a pickup, I also try to measure its Gauss level (with our lab teslameter) and its output voltage - recipe: plug a multimeter to your jack, select AC voltage measurement, set it on "max" in order to record power peaks only, and dig the strings until the value on the screen doesn't rise no more. It works surprisingly well. :naughty:

It was my post of the week if not of the month: I've too busy to keep boring you with my drivel. :laugh2:

More later, maybe, with some of these time consuming attachment files that I add every now and then. Enjoy everybody!

EDIT for an afterthought - here's an excerpt from my master list of pickup specs (easier to find than my disseminated screenshots)...

DCR and inductance of a P.A.F. clone from a well known mainstream brand : 8.6k & 4.85H.

Same data about a P.A.F. clone from a well known boutique winder: 8.4k &… 5.6H (!).

Despite of its lower DCR, we should expect the boutique clone to sound beefier in this case, due to its higher inductance… but even this second spec is now fooling us: actually, the mainstream product sounds mid focused while the boutique pickup has a kind of wide range hi-fi character, with a crisp and clear attack.


There’s a technical explanation: the boutique pickup has way less stray capacitance than the other one.



That’s the kind of differences noticed between average and good pickups and one of the reasons why DCR is definitively not so meaningful. :applause:
 

cooljuk

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Right. The magnets themselves (if not ceramic) and steel cores of the pickups will have a very minor changing result in the response of the coils in an induction test. Nothing like the sonic impact that changing, or especially removing, a magnet has in a complete guitar system, though. I'd love to fine some more ways of testing the whole pickup that would include those without inducing the variables of human playing technique, aging strings, guitar action, humidity, etc. I agree that if you play an instrument enough, and average out the test results, the human inconsistency becomes less of a factor. I do that sort of testing also.

Here's an induction coil test on a 1957 PAF (mostly only measuring the coils, with the magnet and steel parts contributing only marginally to the result): https://www.youtube.com/watch?v=LS6YgFALKjw

The video compares test signals sent through an induction coil to the returned resulting signal from the PAF's excited coils, then also inverts the result against the source for a look at the phase relationship and differences. Not in any way a whole picture of the voice of the pickup, but still interesting!
 

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