Using Aluminum Magnet Wire to Simulate the Lower Quality Copper of Yesteryear?

[capehead]

I have to tell you Possum that since I've been coming around to this part of the forum (my 'home' btw is tube guitar amps), you have in this thread and many others I've read displayed a knowledge about PAF's and vintage style pickups which is absolutely unparalleled in comparison to pretty much anyone else who has actually put it all into words (and those informational YT videos you made were also absolutely enlightening). For sure if I come across anyone looking for a PAF style pickup in the future, yours will be the first on my mind to recommend. As for me, my goal with my recent fling with pickups isn't about duplicating any particular type of sound or even making a business out of it aside from here and there situations; actually the primary reason I built a winding machine was to do tube amp transformers and chokes but since the principle of operation is basically the same and me finally becoming sick to death of the cardboard toned p/u's in my guitars, the intention is to wind some pickups for my current guitars before moving onto the heavy electro-magnetics. I figure though since pickups are my focus at the moment, I might as well have good/in depth information at my disposal that will help make this effort worth while.

As to the topic(s) at hand; this whole metallurgy thing about the copper is one thing but as far as I'm concerned about pole-pieces, I'd use mu-metal or metglas if I could for maximum efficiency in coupling to the coils and use other means of altering the magnetic characteristics. Again, when it comes to creating pups along totally accurate vintage specs and response, I'll leave that to the experts The copper issue is something that holds a particular interest with me in that among every boutique tube amp transformer manufacturer big and small, the possibility that the wire being used to wind transformers prior to 1965 (that includes every Fender amp that is considered classic today) was different in composition has never even been thought of by anyone previously. What you were saying Possum about the enamel having a different dielectric characteristic than modern enamels is also something I will look into at some point soon as this is another important aspect which will impact a coil's interaction with itself; again this is something that could be taken into consideration in winding vintage spec output transformers. You've mentioned Possum that your research into vintage magnet wire is ongoing; would you perhaps be interested in receiving some larger gauge magnet wire samples from pre-1960's transformers? Being that magnet wire of any size comes from the same copper rod feedstock with only the number of drawing stages which vary between the sizes (I believe this is the reason why the AWG scale ascends as the size decreases), it should be the same stuff only larger and easier to analyze, lol. I figure especially on the particularly large diameter wire winds like filaments and output transformer secondaries, even a common microscope (like the kind found in high school science labs) could easily see the 'grain' of the wire in order to visually detect any anomalies within it; with #42 I'm sure would require something like an electron microscope to do the same.

[capehead]

One more thing Possum (or anyone else who might know); would you happen to know around when that purplish/black plain enamel coating started showing up on Gibson pickups or even better simply know what the chemical makeup of this coating is? By using google patent search I think I may have narrowed in on some potential suspects of what PE actually means since the term 'enamel' seems to be not so easily defined.

[salvarsan]

Plain Enamel was discussed at length here a few (7) years ago in a thread on insulation type which may well represent one of the best collaborative research efforts on this forum, i.e., the usual tendencies to start pissing matches were set aside while everyone dug out bits of useful information and contributed them.

This link mentions oleoresin, its natural origin and organometallic hardeners.

[Mike Sulzer]

I'd use mu-metal or metglas if I could for maximum efficiency in coupling to the coils and use other means of altering the magnetic characteristics.

Why? In pickups you are dominated by a magnetic "circuit" made of air since the cores are short rather than forming as closed circuit as in a transformer. Steel, with a permeability of a few hundred raises the inductance over air core by about three at most. It is an asymptotic kind of thing; a material with a mu of thousands will not make that much more difference The rich audible differences seem to relate more to the conductivity of the cores, resulting from the induced eddy currents.

[Possum]

Capehead, thanks. I already have several spools of heavy gauge plain enamel I had to buy to get the other smaller gauges of PE that I wanted, had to buy a group of spools. I have talked to some a couple transformer guys, Merren I think was one, some of them do know the old wire is different, but its not a huge interest to them because you can't get a consistent supply of it enough to design around old wire. He was also aware that old iron isn't the same in old transformers as it is now, it all ties together. Then some old wire doesn't age well, and you sure don't want a power transformer putting out 600 volts with wire that might have insulation breaks somewhere in it. I have a friend who's obsessed with "beano" tone who may have his transformer designer friend wind an OT with vintage wire for him for his JTM45 clone, which will be interesting to see how it compares to his modern OT.

I dont have a clear date on the purple wire, I do have a roll of 42 PE from '54 that is purple, its too oversize to use in buckers unfortunately; I've also seen very purple PE in the early 70's. No idea why the color difference but there has to be a reason. MWS told me the insulation makers will not discuss their products since insulation recipes are highly secret. Interesting enough the first PE that Elektrisola made for MWS was BLACK. Customers complained about the color so now its brown. I know they can make formvar in black because I have several rolls of it, and there were/are rumors that Gibson's BurstBuckers are using colored poly wire, no idea how the coloration is done and they probably wouldn't tell you.

You don't need an electron microscope, a metallurgical microscope is a good piece of gear to have but I've yet to get one, good ones aren't cheap, but I do have a bottom lit microscope with good power, but its difficult to light the metal samples. You have to highly polish the metals to see the grain/crystal structure so its not a simple thing to do anyway, you basically need lapidary grade polishing gear which I used to have but sold off long ago when I gave up jewelry art.

I have experimented with steel similar to mu-metal, somewhat, not as high tech as that, and it does give you interesting results, but it wasn't what I was looking for and the early set I made with that stuff didn't sell well at all, the metal was really expensive too. Audio frequencies and steel is something thats not in any books I ever saw, you have all kinds of alloys used for that. The steel I experimented is what was used in tape recorder heads back when. there's also no books on manipulating audio frequencies with coil winding techniques, I did tons of experiments on both, you eventually get a sense of what things do but also its kind of like grasping straws, not very black and white.

Yeah you should wind some pickups for yourself, StewMac has enough info on the basics and parts you can buy one at a time. Your first pickup will generally sound way better than any factory pickups will. My first one was rewinding a Fender Tele bridge, very rewarding. The more you get into it, the more complilcated it gets though, the learning curve gets steeper and steeper, and it kinda never becomes like Lego blocks, there's mystery in magnets and wire and steel. The wiring harnesses are super important to understand too, vintage harnesses were superior to modern factory harnesses, and had better quality components, its good to study what they did back then.

[Tony Bones]

I think there are at least two possible motivations for studying wonderful old pickups - or anything wonderful for that matter. One motivation is purely academic; a desire to understand better what makes the thing wonderful. The other motivation is to try to clone the thing. One motivation or the other might take precedence depending on who you talk to.

[Joe Gwinn]

And copper has changed the least.

Worst quality copper is 98/99% pure and I'm quite certain (although I couldn't find dates mentioned) that in the 50's all copper used in wire drawing was already electrolytic refined , so 99.9% pure.

In fact i guess it was so already in the 20's or something, go figure.

My point is that difference in **copper** alone is nil, and at worst might be expressed in a less than 1% change in resistivity ... not significant at all.

Even wire drawing diameter shows larger variation than that and definitely has a larger influence.

My point is that I wouldn't lose sleep on that, and concentrate on other parameters which I guess are far more significative.

Maybe somebody can find and post when electrolytic copper refining started being used

As of the chemical ore refining itself, we are working with worse material than before, simply because the best ore got mined first.

New processes allow producers to use , say, 1 to 5% rich ore, when older ones used 10% or higher, but that does not affect us directly: no matter how long and tortuous path it took to reach it, the end of the process is a big chunk of 98/99% "chemical" copper which is electrolytically purified into 99.99% , which is what wire drawers use ... and I guess also used in the 50's .

Exactly.

Another poster mentioned Sulfur. This will be removed by electrolytic refining.

The only other variable is Oxygen. While one can now buy oxygen-free copper (Oxygen-free copper - Wikipedia, the free encyclopedia), nobody makes ordinary magnet wire from it, then or now. Although there are people selling speaker wire of oxygen-free copper -- one supposes that the extra 1% of conductivity makes all the difference. Never mind that going to the next heavier wire diameter will increase conductivity by 10%.

[big_teee]

So to Simplify?
So if the wire is basically the same?
Aren't you back to wire size, (Ohms per Foot), and insulated wire Outside Diameter (OD)?
The Magnets used, the steel in the pickup parts, and the baseplate Composition.
The Rest IMO is Buggy Whips, and Snake Oil!
T

[capehead]

Why? In pickups you are dominated by a magnetic "circuit" made of air since the cores are short rather than forming as closed circuit as in a transformer. Steel, with a permeability of a few hundred raises the inductance over air core by about three at most. It is an asymptotic kind of thing; a material with a mu of thousands will not make that much more difference The rich audible differences seem to relate more to the conductivity of the cores, resulting from the induced eddy currents.

I was more using those materials for the sake of example using the permeability charts as a guide. Although it may be an idea worth looking into/trying out as one attribute I found desirable in mu metal (metglas is far too expensive and limited in availability) is not only does the permeability approach that of pure iron but it's characteristic of being magnetized and demagnitized very quickly I think might make for a more sensitive pickup as even the most subtle string vibrations will be passed along more efficiently to the coil; or so my theory at the moment goes.

[rjb]

Steel, with a permeability of a few hundred raises the inductance over air core by about three at most. It is an asymptotic kind of thing

Help. I'm in over my head (again).

First, I had to remind myself what "asymptotic" means Asymptotic analysis - Wikipedia, the free encyclopedia
"In mathematical analysis, asymptotic analysis is a method of describing limiting behavior."

So, was the simple equation they told me in high school physics for the inductance of a solenoid completely bogus?
Is a pickup polepiece too short to fit the "long solenoid approximation"?
Inductance of a solenoid
Magnets and Electromagnets

To put things in practical Neanderthal terms:
Say I want to wind an inductor in the range 15-16 Henry on a 1/4" steel bolt core.
I might be able to determine the class of steel, and can order any size magnet wire.
How can I determine a ballpark figure for the number of turns required?

My apologies for side-tracking the thread.

[David King]

No RJB,

I think you are on to something. How hard would it be to take empirical data from a bunch of pickups and come up with a simple excel inductance calculator for say a strat coil or a slug coil of a humbucker. I'd love to own an Extech but honestly I'd probably only use it for a few months before I'd get a pretty good sense of what result i was going to get from it and toss it to the back of the drawer.

[Mike Sulzer]

Sorry to be confusing. I just meant that continuing to make the permeability bigger has little additional effect. Here is where the concept of reluctance of a magnetic circuit can be helpful. It is kind of like resistance in an electrical circuit. Suppose you put two resistors of equal value in series and connect a battery. You get some current. If you make one smaller the current goes up, but once the one you are changing is small compared to the other, making it still smaller has little additional effect. That second hyper physics link has me confused; if what they are saying is literally true, it would imply that you could make a good audio transformer with just a cylinder of material, but actually you need a closed geometry, such as a toroid or the square kind to take full advantage of the permeability of the material and keep leakage inductance low. Maybe Joe Gwinn could further clarify this.

I know how to determine the inductance of an air core solenoid, but I think it is not so easy with a high permeability core.

On another discussion I recently posted some measurements of the impedance (and the inductance is written on the plot) with steel and alnico. Alnico is maybe 6 and steel maybe a couple hundred, but the difference in inductance was not that large, just over a factor of two.

Help. I'm in over my head (again).

First, I had to remind myself what "asymptotic" means Asymptotic analysis - Wikipedia, the free encyclopedia
"In mathematical analysis, asymptotic analysis is a method of describing limiting behavior."

So, was the simple equation they told me in high school physics for the inductance of a solenoid completely bogus?
Is a pickup polepiece too short to fit the "long solenoid approximation"?
Inductance of a solenoid
Magnets and Electromagnets

To put things in practical Neanderthal terms:
Say I want to wind an inductor in the range 15-16 Henry on a 1/4" steel bolt core.
I might be able to determine the class of steel, and can order any size magnet wire.
How can I determine a ballpark figure for the number of turns required?

My apologies for side-tracking the thread.

[salvarsan]

The Rest IMO is Buggy Whips, and Snake Oil!T

Don't forget magic. ...and mojo, too.

[salvarsan]

Wire, we here

The Metallurgy of Copper over at Copper.org is a good gloss on refining and testing copper.

Oxygen is injected to sequester impurities as oxides, the bulk of which are wiped off the melt.
The melt is kept under low vacuum and/or inert gas to limit the total oxygen uptake.

[salvarsan]

If buggy whips seem too modern, there is the nerba, a stretched tanned bull penis for similar application.

Apparently, nerbas made from the Chianina bulls sound better.