Rick's 38ga 1000wind bucker challenge

[CRU JONES]

Well, This may be a good time to start a new thread from the "pickup theory question" thread.

38ga 1000 winds each coil TPL random between 10 and 60.

All measurements besides d.c. resistance done at 1000Hz.

slug side:
air coil
189 ohms D.C.
312 ohms a.c.
39.4mH
w/ 1010 non plated slugs
502 a.c.
71.5mH

Screw Side:
Air coil
184 ohms D.C.
302 ohms a.c.
38.4mH
Screws + keeper
490 ohms a.c.
67mH

series connected w/o magnet:
484 ohms
1.073Kohms a.c.
152mH

series connected w polished UOA5 magnet (charged)
1.125K ohms a.c.
160.9mH

series connected w polished A2 (charged)
1.155K ohms a.c.
166.4mH

I haven't put it in a guitar yet. Curious how these numbers jive with yours, Rick.

I would like to encourage others to take a moment to do the same and add to this thread, though I realize not everyone is likely to have 38ga on hand.

Cru

note: one coil was wound without an acceleration ramp.

[JGundry]

Are you hand winding these?

[Rick Turner]

When I did the Litz wire pickups...about 21 years ago...I was only measuring DCR and it came to about 600 Ohms per coil with about 1,200 turns of 7x44ga. The real issue here is getting the coil self resonance way up and out of the way of the audio band, so I'm not sure that the impedance/inductance really matters all that much any more. I only suggested 1,000 turns of 38 because that will certainly yield a low impedance, wide bandwidth coil.

To make the test really count, the trick would be to wind just enough fat wire so the physical space taken up by the coil is as close as possible to that of the archetypal pickup...in this case, a PAF. You want the same mass of wire cutting through the flux field, though the turns will be less.

I'd be jumping into some of this myself, but I'm just buried trying to get ready for NAMM. I do have more of the Litz wire to muck about with when I get time. I know, I know, it's not supposed to make any difference at audio frequencies, but the pickups sure sounded cool. I did a Guild Starfire bass with the Hagstrom pickup rewound in Litz, took the signal out as a balanced line, and my friend Dan plays it through a really high quality EAR (Esoteric Audio Research) tube microphone preamp. As one of my old editors at Bass Player said, "You can hear your fingerprints with this...but it makes bad strings really sound bad!" I think that's the kind of coil resolution that may allow us to quantify (or not) tonal differences from magnet changes.

[CRU JONES]

Are you hand winding these?

No Sir.

These are some exciting numbers, no?

Cru

[peskywinnets]

What frequency are you using for the AC resistance data? (& how are you measuring it?)

[David Schwab]

slug side:
air coil

Which is it? Do you have slugs or not? An "air coil" has no metal core.

[CRU JONES]

@Pesky: All measurements are done at 1KHz. On prototype equipment. You have to get me to drinking for me to talk about it. Should be good though.

@ Rick: No worries man. Tell me what to do with this pickup! From how I understand it, I am going to put it in my guitar, record a little ditty with for a sampling of magnets, and see what happens. I had it in mind to record them into my DAW and Normalize the audio. Seems like this would be a good way to eliminate the amplitude differences caused by field intensity, and isolate the magnet?

@Dave: Yeah, good point. I tried to edit the first post to make the format more readable, but couldn't. The "air coil" measurement was done on the slug side bobbin before I pushed the slugs in. Then I give a new set of measurements with the core inserted. The screw side follows that same form.
This might also be interesting:

1000 winds 42ga:
Slug Bobbin:
Air coil/ no core
40.44mH

1010 slugs inserted in bobbin
80.62mH

Sorry, I forgot to write down a.c. resistance.

[JGundry]

No Sir.

These are some exciting numbers, no?

Cru

Honestly I commend your enthusiasm but I'm not excited. If this is a test as it relates to PAF's I frankly think winding something that is in PAF spec. territory is the only way to get a meaningful result if the goal is to see how different magnets sound in PAF's. But if you are interested in low impedance pickups this is a cool experiment. I have a prediction though. I'm guessing that you will find that Alnico with the highest copper content will yield the fullest sounding pickup and that the ceramic will yield the harshest. If so I would chalk it up to inductance differences created by the two.

[Rick Turner]

Jon, you're missing the whole point. This isn't "about PAFs", it's about magnets and whether we can hear the difference among various magnet types independently of the limitations of high impedance coils. I know that you are all about PAF clones and "mojo", and that's OK, but if you could widen your viewpoint and stimulate your own curiosity just a bit, you might be able to contribute something to our overall understanding of what's going on with the apparent tonal variations that happen due to magnet changes. Maybe it is simply a matter of inductance and so the tonal changes only happen audibly with high impedance coils, but maybe it's not just an inductive change and there's something here that we can all learn about why pickups sound as they do.

And maybe you'd not like for yet another factor that goes into pickups to be understood by a group of people because it's easier to talk about mojo than about quantifiable elements of our art and science.

[JGundry]

I do get it Rick. I do think it is a potentially interesting test. But I do think the big flaw in any inductance reading as it relates to different magnets is the limit of testing just one or two frequencies. You really need to have readings that cover the entire range a guitar can produce. I know from my own tests that there is much more subtlety to the inductance variation created by different Alnico magnets than the two frequencies covered by an LCR meter. They just don't offer enough resolution to paint a detailed tonal picture.

But still I do think this exercise has merit..

[Rick Turner]

I would hope that with a low impedance coil, issues of inductance become fairly irrelevant in the audio band. I want the coil basically out of the picture for the purpose of hearing magnets, and if it turns out that there's no difference when listening to low impedance coils, then we've learned something right there...that magnet swaps change tone only through their effect on inductance, and that it probably has nothing to do with magnetic field shape changing. I'm hoping we can eliminate some factors as well as perhaps find some new ones. If we just look at inductance within the audio band with high impedance coils, I think we're going to miss something interesting...or eliminate some misunderstandings.

[CRU JONES]

Hi all,

This is an easy test to do. The point seems to be to wind a coil, play it, and listen. I liked Rick's test idea because It seems you don't need any equipment (besides a wind counter) to be a part of a discussion.

Cru

[Rick Turner]

This gets to the heart of "listen first, measure second", and in this case the idea is literally not to hear the effect of the coil limiting bandwidth. If magnet changes only affect inductance, then with a low Z coil, you shouldn't hear any difference among the magnets as the inductance changes will affect resonance and roll off way above audio frequencies.

[JGundry]

I guess I'm confused as to how you are going to do a playing test with these. Is this going to be clean or distorted tones? I would assume clean which I think is pretty limiting in terms of an audio test of an electric pickup. I think a lot of tonal differences surface with distorted tones.

I can honestly say that I have no experience with low impedance pickups other than never playing one that I liked. But would I be correct that a low Z pickup has flat frequency response with a much lower Q? And that for this test to have enough resolution you have to have a big enough Q to get the same relative dynamic range out of the low z pickup as you would get with a higher impedance pickup. I may be full of shit though so let me know if I'm wrong about the Q. Maybe I should be putting this in terms of output signal amplitude an not Q?

[Rick Turner]

Jon, I really think you've completely and utterly missed the whole point of my proposed experiments. This has very little to do with making a great sounding pickup...with all the usual characteristics imposed by inductance. The idea here is simply to test the theories about if and how different magnets may have their own sonic character independent of their effect on coil resonance and response. Start with a coil (or two) that have whatever low end response you may get given that they don't go to DC, and wind only as many turns as puts the coil resonance and subsequent roll off above 20 K Hz.

Now that you have a much more (relatively speaking) flat response coil, use some sort of preamplification to equalize the voltage level, and now test for tone and measure...if you can.

My suspicion is that you may hear tonal differences that simply do not show up with the methods used by most people to test pickups. A signal coil driving a pickup is simply NOT a string. I suspect that there is a kind of dynamic geometry going on between real strings and real pickups that adds a signature to the sound of the pickup that is entirely separate from all the coil winding "mojo".

My suggested tests are intended to reveal another layer of the sonic onion or to prove that it doesn't exist. It does take into account (to a certain extent) the aperture of the pickup as partially defined by the shape of the magnetic field...and think about that very word "shape". Magnetic fields have a three dimensional shape and density in space, and the pickup's magnet(s) and the strings modulate that shape and density. The magnetic circuit applies a kind of magnetic bias to the string along a certain part of its length. The string modulates that bias and that's turned into a current in the coil. And different parts (turns) of the coil are actually seeing a different picture based on the aperture of the string that they "see" and how far away from the strings the turns are. For instance, the turns farthest away from the strings contribute less to the signal than do the turns that are closer. Pole pieces can help induce more flux variation down to the lower turns of the coil. That's one of the brilliant things about the classic horseshoe pickup...it's very efficient, in part because the horseshoes help couple string motion to the lower turns in the coil.

So please try to understand that this whole proposal is NOT about making a better sounding PAF; it's about better understanding if and how different kinds of magnets might affect tone INDEPENDENT of the sonic limitations of high impedance coils. If there's something to be learned here, it will certainly apply to and bring us a greater understanding of how high impedance pickups work, too.