How does the material a pickup is made from affect tone?

[gui_tarzan]

I've never really thought about this until recently aside from the marketing aspects but I've been watching a lot of videos and reading a lot of articles/interviews about people like Eddie Van Halen (not just him), that that have had companies design pickups for certain tone qualities. I've always understood the resistance to be a factor in the power output, i.e. what makes a pickup "hot" or "mild" and I understand that different magnets affect the tone, but how?

How do the materials used in a pickup affect tone? It's wire wrapped around a core with a magnet that creates an AC signal when the strings vibrate near it. The tone part is a mystery to me.

[Mark Hammer]

Which materials? Apart from the silver-wire pickups Seymour Duncan makes, copper is copper, when it comes to the wire forming the coil, but the coating that insulates it can have different thicknesses, depending on the material involved. Thicker and thinner coatings have implications for how many turns are, or can fit, on a standard-sized coil. When it comes to humbuckers, the material used for the baseplate can matter, as well as the cover. And some makers are very picky abut the bobbin material.

As many here will likely note, resistance is only a fairly indirect indicator of the things that DO matter,when it comes to tone. It can be useful for quickly comparing pickups when a number of other things are held constant, but does not mean much on its. I was recently given an early '70s Sears guitar, whose pickups measured around 4.3k, and they are surprisingly loud.

[salvarsan]

Which materials? Apart from the silver-wire pickups Seymour Duncan makes, . . .

This is a deep one.
The Duncan Zephyr pickups had poles made of nickel over 430 solenoid alloy core for a unique layered permeability. Whatever. They liked its sound the best.

Bobbins were a glass-filled nylon? for low microphonics and dimensional stability, a step up from the usual ABS pieces.

Everything you do makes a difference in the tone -- it's not just the carrots and bay leaves that make the stew.

-drh

[gui_tarzan]

That's what I'm asking. How do the individual materials affect the tone? I know how the wood does, I've built several guitars from scratch (many years ago) using different woods but the pickups have several parts and are there to generate the electrical signal - at the most basic level.

So how does the magnet type affect tone? Is it because the magnetic field properties generate complimentary (or not) harmonic frequencies in different ways? How does the bobbin material affect tone? How can the base plate affect tone? What makes a pickup sound warm vs brittle?

This is something I'm honestly trying to understand, trying to wrap my brain around like how AC and DC can live on the same wire at the same time. That one still mystifies me. I accept it, but don't quite understand the physics of it.

[Mark Hammer]

There are many pharmaceuticals out there that work, but no one really knows exactly how they do. All we know is that they "work", and we know (most of) what their potential side-effects and drug interactions may be. And they aren't necessarily obscure drugs, either. Aspirin (acetylsalisilic acid) is one of those.

So as much as I don't disparage your question, the actual mechanics/physics or chemistry behind many of these elements is still a mystery to many. It often tends to operate by the principle of "How is this great vintage pickup different than others?", and people implementing one or more of the elements of that and liking what the hear without necessarily knowing why it does that.

[Antigua]

I've never really thought about this until recently aside from the marketing aspects but I've been watching a lot of videos and reading a lot of articles/interviews about people like Eddie Van Halen (not just him), that that have had companies design pickups for certain tone qualities. I've always understood the resistance to be a factor in the power output, i.e. what makes a pickup "hot" or "mild" and I understand that different magnets affect the tone, but how?

How do the materials used in a pickup affect tone? It's wire wrapped around a core with a magnet that creates an AC signal when the strings vibrate near it. The tone part is a mystery to me.

It's not complicated in terms of the number of factors involved, but the math which connects the factors together is complicated because it involves geometry, change over time and circuit analysis. Even though guitar pickups have been around for seventy or eighty years, there haven't been too many people with an engineering background to come along and offer up information. Helmuth Lemme and Manfred Zollner probably have come closest to offering comprehensive technical information about how guitar pickups work https://www.scribd.com/document/4903...nfred-Zollner# , but with guitar pickups, most people feel that there's no pressing problems or shortcomings to be solved (aside from trying to capture the ellusive haunting mids) , so there's not much money to be made in this research. You can barely give it away for free.



With a high impedance pickup, usually the most characteristic part of the sound is the resonant peak, which puts an emphasis on the output amplitude at a particular frequency. The reason a Seymour Duncan JB sounds difference than a '59 or a "Jazz" is almost, if not, entirely due to the difference in resonant peak, caused by the JB having more copper wire turns, and therefore a higher inductance than the '59 or the Jazz, but otherwise these pickups are nearly identical. In situ, the JB has a resonant peak that is about 1kHz lower than the '59 or Jazz, and it's known as a hot pickup, where has the '59 and Jazz are described as "vintage output". Note that the peak frequency is not fixed in place, but it moves around depending on the overall circuit capacitance, which is mostly varied by the choice of guitar cable, which have different capacitances along their lengths. So when you use a long guitar cable, the resonant peak of the pickup drops, as there is no buffering in between to allow the pickup to act as an isolated filter. This is where the circuit analysis comes into it.

It's not just the turns of wire that determines the inductance though, this is where material starts to matter. If the core of the coil, or even it's surrounding metal parts, are permeable, then they will enhance the formation of magnetic fields around the coil, and this will cause the inductance to increase also. A permeable core can more than triple the inductance of the pickup. From this perspective, pickups have a lot in common with inductors, so if you read up on how a core effects an inductor, you will also understand why it affects the inductance of a pickup.

With pickup there are two common types of core, a steel core like you have with PAF slugs and screws, or P-90s or single coil pickups with steel slugs and magnet glued to the bottom, and the other common type if AlNiCo pole pieces, almost exclusively in Fender single coils. The permeability of steel is much higher than AlNiCo, and the difference is in orders of magnitude. So if you have a Fender single coil, it measures 2 henries inductance, if you push the AlNiCo magnets out, and have no core (called air core) the inductance will drop to about 1 henry. Then, if you shove steel pole pieces into the pickup (assuming this doesn't cause the pickup to break) the higher permeability of the steel will increase the inductance to about 3 henries. As the inductance decreases and increases, the resonant peak frequency becomes higher and lower respectively, so at each stage, the amount of mids and brightness the pickup would produce would change dramatically. Even though the steel is far more permeable than AlNiCo, because the magnetic path is incomplete, and is mostly made of the air space around the pickup, an increase in inductance that is also orders of magnitude can't be realized, but if you look at inductor design, you can see that they make the effort to displace more of the air around the coil with permeable material, to get the most band for their buck.

The inductance is probably the most important thing, but next comes the Q factor, which is how peaky the resonant peak is. The higher the Q factor, the more amplitude of sound at that frequency, so if the peak freq. is 2kHz, and the pickup as a high Q factor, you will hear a lot of sound at 2kHz, the guitar's harmonics around 2kHz will be emphasized in the output sound. A little bit of emphasis is what gives an electric guitar it's famous sound, but too much emphasis / too much Q factor causes the sound to be overbearing in the treble. This is the reason guitars don't all use 1 meg control pots, because they produce a maximum Q factor, where as 500k or 250k pots put a lower resistance across the pickup, retard the LC resonance and bring the Q factor down. The lower the resistance of the pot, the lower the Q will be. So Fender uses 250k pots in order to bring the Q factor of their single coils down significantly, where as Gibson uses 500k pots to bring the Q factor down less so.




This brings up the third consideration with materials, why does the Fender need 250k pots and the Gibson need 500k? Another factor that reduces the Q factor is "eddy currents". When the magnetic field alternates, eddy currents form in all the conductive metals in and around the pickup, and the circuit analysis, they present as a resistance across the pickup, so just as the 250k pot lowers the Q factor more than 500k, the presence of some eddy currents lower the Q factor more than no eddy currents.

Fender single coils, with their AlNiCo pole pieces, exhibit less eddy currents than pickups with steel screws and pole pieces, because AlNiCo is less conductive than electrical steel, and again I think the difference is in orders of magnitude. So for this reason, the Fender AlNiCo poled pickup naturally has less eddy currents in its metal, and a higher Q factor all things being equal. This is why Fender uses 250k pots and Gibson uses 300k or 500k, because Fender has to compensate more the lower the Q of their naturally high Q single coil. For the Jaguar and Jazzmaster, they did use 1 meg pots, but only because for whatever reason they were trying to embrace the high Q factor tone, and those guitars featured switches and knobs to lower the Q factor, but for the most part the guitar makers pair 250k for AlNiCo singles and 500k for humbuckers, to reduce the Q factor down from a tall peak to a nice little hill on the response curve. We have found from testing pickups that Filter'trons, with their twelve big fat screws have the highest eddy currents among the common vintage pickup designs, but nothing will probably ever beat the Lace Alumitone, being that it's a thick chunk of aluminum.

The last important thing, before it really start to drop off in terms of importance, is the cover. In the same way that AlNiCo is less conductive than steel, in the case of covers, nickel silver is less conductive than brass, and these are the two common materials used for making pickup covers. The brass covers cause a significant drop in Q factor, but the nickel silver covers don't cause much drop at all. So if you have a humbucker or Tele neck pickup, and it has a brass cover, and you remove the cover, it will become audibly brighter as a result of a higher Q factor, but if it has / had a nickel silver cover, you won't hear much difference, it will have already had the higher Q factor. Fender's modern Tele neck pickup has a nickel silver cover, but in the past they had brass covers, and that caused people like Jimi Hendrix to famously hate it, while I think Jazz players liked the smooth tone. If you just turn the tone control down to about 7 or 8, you can lower the Q factor in a way that makes it sound like your pickup has a brass cover.

This plot shows how the Q drops with the tone control being turned down, and you can see how if a pickup has a high Q factor, the tone control or the pot values of the guitar can lower the Q factor, the same as if they pickup has losses as a result of eddy currents. Notice that the Q factor increases at zero, this is because at zero, the tone control's 470nF or 200nF capacitor becomes fully parallel with the pickup without resistance in between, and so its like a very very long guitar cable, it lowers the resonant peak of the pickup, down below 1kHz






When you consider how constrained the parameters are, and that most of the pickups on the market have an identical foot print and near identical electrical values, the truth is that most of those pickups sound identical, but a lot of psychology plays into perception. A Seymour Duncan and a boutique humbucker might actually sound the same, but people will have a different feeling about what they represent and perceived quality, so they will describe them with different adjectives, often using words they've seen other people use on guitar forums.

A lot of people make a big deal out of the magnet type. In a Fender single coil, there is something to this, AlNiCo 2 and 3 are more permeable and conductive than AlNiCo 5, so that if the Fender single coil has A2 or A3, it's inductance will be higher, and its Q factor lower, all else being equal. For example, if you have a Fender single coil with A5 and it measures 2 henries, if you pushed the A5 poles out and pushed A2 poles in, it would read closer 2.3 henries thereafter. The stronger magnetic field causes a greater magnetic attraction between the guitar pickup and the strings, and that causes some higher harmonics to be induced in the string, and this why the tone changes as you raise or lower the pickup from the strings. It's debatable whether there is a real distinction in the outcome between using a stronger magnet, versus just setting the pickup close to the strings. If there is a difference, it's very subtle.


Other materials get talked about, such as fiber flatwork versus molded plastic, or butyrate verses modern plastic, these materials are electrically inert, so it's just a matter of authenticity in vintage pickup reproduction, and not having much to do with tone. Some say there's a difference in plain enamel versus poly insulated magnet wire, and these are not inert because of the capacitance dielectric effect of the wire insulator, but the truth is that their dielectric values are very close together anyway, and you don't see much if any variance in capacitance in pickups depending on which is used. What's more likely to make a difference is the thickness of the insulation, because if its thick, you end up with more coil area for fewer turns of wire, resulting in a lower capacitance and a higher inductance, but again, not much of a difference, on account of the overall geometry being nearly unchanged. If you compare a Jazzmaster and a Strat pickup, even with the same wire and dc resistance, the inductance and capacitances are very different, because the geometry of these two pickups are so different, the Jazzmaster having a flat and wide coil results in about a quarter of the capacitance and about a quarter higher inductance for the same amount of wire.

I could keep rambling but I'll cut myself off here.

[gui_tarzan]

Now THAT is what I was looking for. Thank you. Some of that I knew, most of it I didn't. I certainly did NOT know this:

"This is the reason guitars don't all use 1 meg control pots, because they produce a maximum Q factor, where as 500k or 250k pots put a lower resistance across the pickup, retard the LC resonance and bring the Q factor down. The lower the resistance of the pot, the lower the Q will be. So Fender uses 250k pots in order to bring the Q factor of their single coils down significantly, where as Gibson uses 500k pots to bring the Q factor down less so."

That answers a question I've had for years.

So in the grand scheme, when a humbucker pickup is wound and let's say it has flat, non-adjustable poles or strips, it wouldn't matter if you put it in one way or the other (normal or rotated 180 degrees) because the winding isn't designed to work differently from the high E side to the low E side, correct? The reason I ask is because on some of EVH's guitars in the 90s he flipped the neck pickup 180 degrees and believed it gave it a "fuller" sound. I call BS, but I've never tried it. Someone posted this on a different forum earlier today:

"Jim DeCola cited that this produced a “deeper” tone in that position."

I still have my doubts.

[eschertron]

The reason I ask is because on some of EVH's guitars in the 90s he flipped the neck pickup 180 degrees and believed it gave it a "fuller" sound.

And we're back to boring ol' engineering. Are the two coils wound exactly the same? What's the tolerance in each of the coils' measurable parameters? Any pickup with a measurable difference between the coils may have an audible difference in sound. Does one coil have adjustable polepieces and the other not? Raising or lowering the screws will absolutely change the tone; moving that control surface a fraction of an inch along the string length (by flipping it around) will affect the way the pick senses the [relative strength of the partials that make up the] vibrations in the string. Tone changed. I believe much of what Eddie did to his axe was as a result of experimentation, not calculation.

[gui_tarzan]

Oh I am certain it was from experimenting, he stated that many, many times in interviews. Plus he had manufacturers customizing everything for him. It's pretty fascinating.

[Antigua]

So in the grand scheme, when a humbucker pickup is wound and let's say it has flat, non-adjustable poles or strips, it wouldn't matter if you put it in one way or the other (normal or rotated 180 degrees) because the winding isn't designed to work differently from the high E side to the low E side, correct? The reason I ask is because on some of EVH's guitars in the 90s he flipped the neck pickup 180 degrees and believed it gave it a "fuller" sound. I call BS, but I've never tried it. Someone posted this on a different forum earlier today:

"Jim DeCola cited that this produced a “deeper” tone in that position."

I still have my doubts.

IMO, it takes so long to change around a pickup, more than a few seconds, enough time will have passed that you won't remember exactly how it sounded before (also keeping in mind that how it sounds is a secondary consequence of how you play the guitar), so if you're inclined to think there's a difference, it's easy to believe there's a difference.

If the humbucker has poles and screws, someone might think there's a difference in how receptive the two coils are based on the visual difference. Just looking at the size of the slugs, someone might assume that coil must be more productive than the coil with the screws, and it's maybe it is or it isn't, someone might make assumptions all the same. I'd assume that it actually is, especially given the fact that it can be demonstrated that especially long screws reduce the magnetic field strength of the screws, while the slugs have no excess length, but the difference is probably so small that it's not audibly perceptible. It would be like lowering a pickup by half a screw turn and expecting to hear a difference. In audio studies it's said that if a loudness varies by less than 1dB, a human can't perceive it, and in a noisy environment, it's probably somewhere between 2dB and 3dB before you can tell a difference, so a lot of ways in which pickups are tweaked will make a difference on paper, but the difference will end up being below the 1 or 2dB threshold where a human could perceive the difference.

An interesting fact about humbucker coils is that when wired in series, the coil with higher inductance will be louder in the final output, but if you wire the humbucker in series, the higher inductance coil becomes the quieter one, because the higher inductance coil then becomes loaded down by the lower inductance coil in that circuit scheme. So if you wind a coil hotter in order to get sonic distinctiveness, it's only hotter in series. I'm sure Van Halen ran humbuckers in series most all the time.

[jackywang1010]

This is really complicated, because our company is a magnet manufacturer, and we didn’t pay much attention to guitar pickups before. Over the years, many customers have complained about our minimum order quantity and other issues. This year, the boss said that we should make some changes. Recently I am learning some knowledge in this area, in order to write some articles for our website SEO work, and I found that the working principle of the pickup does not sound complicated, but it is incompatible with my knowledge of magnetic materials. I have a little difficulty even reading your discussions because English is not my native language. Thank you for your information help me learn something. if you need any help on the magnet, I can supply some support.

[bbsailor]

For those MEF members tinkering with Current Transformer (CT) pickups, the string loop wire type and gauge will affect the tone and output level of the pickup.

The skin effect defines the maximum frequency that will go to 100 percent of the wire depth and produce the most current which gets converted to an output voltage based on the number of turns of wire in the CT.

AWG10 .1019 inch diameter, 2600 Hz skin depth
AWG8. .1285 inch diameter, 1650 Hz skin depth
AWG6. .162 inch diameter, 1100 Hz skin depth
AWG4. .2043 inch diameter, 650 Hz skin depth

Using stranded wire will minimize the skin effect, but affects the ability to make a very low resistance string loop joint for the wire going through the CT.

The type of magnet chosen for the CT based pickup will affect the following.

1 Output level with neo magnets produces a higher output level.
2. Magnet coating with epoxy being better when using non insulated wire for the string loop. Metal coated magnets will need a tape covering to prevent shorting out the string loop and will have eddy currents generated in the metal coating to affect the sound.
3. A stepped magnet shape will have a groove along the length of the magnet on the long side to allow the string loop wire to be securely attached to the magnet.
4. Magnet size should be about .25 inch tall to allow the pickup to be tried on many guitars with no cutouts. The magnet length should be 2.25 inch to ensure that the two outer guitar E strings, spaced 2 inches apart, are in a full magnetic field. A magnet width of .375 inch should work well, but try what ever you have or can easily get.

Let your ears affect your design, then take good measurements to move the variables all in the same right direction.

Joseph J. Rogowski

[Antigua]

This is really complicated, because our company is a magnet manufacturer, and we didn’t pay much attention to guitar pickups before. Over the years, many customers have complained about our minimum order quantity and other issues. This year, the boss said that we should make some changes. Recently I am learning some knowledge in this area, in order to write some articles for our website SEO work, and I found that the working principle of the pickup does not sound complicated, but it is incompatible with my knowledge of magnetic materials. I have a little difficulty even reading your discussions because English is not my native language. Thank you for your information help me learn something. if you need any help on the magnet, I can supply some support.

Guitar players have big imaginations. If you sell a lot of different types of magnets, they might buy the magnets randomly and them imagine how they make the pickup sound different. They will then go on the internet and tell other people how they believe the sound is made different, and other people will believe it, they will buy those magnets also, and then also imagine that what they hear is in agreement with what they read on the internet. It's not necessary for there to be any real difference in the sound, guitar players will tend to believe they sound different anyway. You will almost never see guitarists say that two pieces of equipment sound the same as one another, the tendency is to believe everything sounds different.

[jackywang1010]

Guitar players have big imaginations. If you sell a lot of different types of magnets, they might buy the magnets randomly and them imagine how they make the pickup sound different. They will then go on the internet and tell other people how they believe the sound is made different, and other people will believe it, they will buy those magnets also, and then also imagine that what they hear is in agreement with what they read on the internet. It's not necessary for there to be any real difference in the sound, guitar players will tend to believe they sound different anyway. You will almost never see guitarists say that two pieces of equipment sound the same as one another, the tendency is to believe everything sounds different.

It's true. I've been watching many videos of guitar players recently, but as a layman, I really can't tell the difference between different magnets. Recently, I have some pickup maker customers communicating about different performance grades of magnets and different magnetization directions for their guitar pickup design. But they usually buy in very small quantities, so I'm also looking for ways to provide them with samples. Because I really don’t know anything about pickups themselves, it’s quite difficult to communicate. I can only give advice on magnet performance, but I can't translate it into data at all. This is completely different from my other types of clients.

[Brian W.]

Not having a chart nearby makes it impossible to site any percentages of aluminum, cobalt, etc. etc. that make up the different rod magnets for Fender pickups but how do the differences in A5 , A4, A3, A2 manifest in the sound of the particular pickup?
Would a higher percentage of cobalt impart more treble ??