Measuring the Electrical Properties of Guitar Pickups

[straylight]

If the ground side of the coil is on the inside close to the magnets, grounding the magnets like that does very little. If the ground side of the coil is on the the outside grounding the coils like this gives you some inductive coupling to earth, and drops the Q, it's measurable on one coil of a 4+shield humbucker more readily.

[wayne]

I realize this is an old post, but hoping someone is still paying attention to it.  I love the idea of measuring the frequency response of pickups, but am a complete newbie to it and have some very basic questions that I was hoping someone could assist with:

1.) For the driver coils made out of an old pickup, if you remove the pole pieces, whats left to hold the bobbin together? Isn't it just the pole pieces that hold the top and bottom together? EDIT:  Opps, I saw on an earlier post that you had a special pickup with plastic connecting the top and bottom of the Bobbin. Also, I’m assuming the brass eyelets need to be removed or they interfere with the measurements?
  I suppose I could just super glue the top and bottom of the bobbin to a small smooth blank of wood and wind it as described?
2.) Also, where was the tiny driver coil on a Popsicle stick used?


Thanks for any advice you can offer.

[antigua]

Jun 12, 2020 18:56:41 GMT -5 wayne said:

I realize this is an old post, but hoping someone is still paying attention to it.  I love the idea of measuring the frequency response of pickups, but am a complete newbie to it and have some very basic questions that I was hoping someone could assist with:

1.) For the driver coils made out of an old pickup, if you remove the pole pieces, whats left to hold the bobbin together? Isn't it just the pole pieces that hold the top and bottom together? EDIT:  Opps, I saw on an earlier post that you had a special pickup with plastic connecting the top and bottom of the Bobbin. Also, I’m assuming the brass eyelets need to be removed or they interfere with the measurements?
  I suppose I could just super glue the top and bottom of the bobbin to a small smooth blank of wood and wind it as described?
2.) Also, where was the tiny driver coil on a Popsicle stick used?


Thanks for any advice you can offer.

The brass eyelets are too small to have any impact.

The Popsicle stick coil replaced the pickup sized coil. Technically the guitar string is better represented by a tiny coil. If you're doing general purpose bode plots of a pickup, it doesn't matter how large the driver coil is, but if you try to do more specific testing, such as shading a particular pole piece with foil, you have to use a small driver coil in order to limit the magnetic field to that one particular pole piece. 

[phildefer]

Hello,

I used the provided method to make some measurement on different stratocaster pickups (bridge) and then I wanted to improve the response of one of my pickup (the E string was a little weak), so I decided to increase magnetics strengh of the pickup magnet passing it between two neodyme magnet (north-south).

The result is displayed in the following picture. 

I have some questions. What is impact of such magnetics increase on the sound ? Is there any risk for the pickup magnet ? Is there some normative values for stratocaster pickups. How to restore the initial situation coming back to the intial curve.

Thanks in advance for your comments.

[antigua]

Oct 4, 2020 15:15:49 GMT -5 phildefer said:

Hello,

I used the provided method to make some measurement on different stratocaster pickups (bridge) and then I wanted to improve the response of one of my pickup (the E string was a little weak), so I decided to increase magnetics strengh of the pickup magnet passing it between two neodyme magnet (north-south).

The result is displayed in the following picture. 

I have some questions. What is impact of such magnetics increase on the sound ? Is there any risk for the pickup magnet ? Is there some normative values for stratocaster pickups. How to restore the initial situation coming back to the intial curve.

Thanks in advance for your comments.

Charging the magnets doesn't increased the coupling efficiency of the pickup, so the higher output voltage much be due to something else changing between tests, either the test coil being in a different position in relation to the pickup, or the test voltage was changed, or maybe the 1x / 10x switch on the meter probe got bumped. The only conceivable change you would observe from charging the magnetic is that the inductance would drop very slightly (because charging the magnet locks a portion of the magnetic domains into a particular orientation, therefore unable to react with the coil), and move the peak frequency to a higher value, but that would probably be barely noticeable, given the lower resolution of the plotter. 

There's no risk to the magnets, the worst you might do is charge them with the wrong magnetic orientation, and then when you installed the pickups, the hot and ground wires would have to be reversed in order to keep it "in phase" with the other pickups. If you have a compass on hand, you can note the initial polarity of the magnets, and make sure it's returned to that polarity after testing. 

It's most likely the case that the pickups were fully charged to begin with, unless they were very old or had been demagnetized on purpose. In general, if the magnet is stronger, the tone will be brighter. The magnetic string pull promotes higher harmonic amplitudes at the expensive of lower harmonics. That distribution of harmonic shift is uneven, since the pickup is in an arbitrary location below the strings, and that constitutes a change in the overall timbre, so the say that it increases treble is an accurate but incomplete description.

[phildefer]

Thank you very much for the analysis, further to some checking,  the issue came from measurement error (10 x probe option changed by inadvertance). So the final plot is the following with two pickup hand wound which are quite similar and another one from a mexican strat. it confirms that magnetic changes I did has almost no effects.

[pablogilberto]

Hey Gnuts!

I've been measuring PAF style pus and wanted to get your insights.
Based on my collected data, the Inductance of typical PAF is around 4 to 5 Henry.
But I do get a few which are as high as 8 Henry.

My question is, in your experience, what is the best electrical parameter value combination for a Neck and Bridge pickup to get a similar response and output level? Is it safe that both pickups should have a similar RLC values?

Is there good reason for having a Neck that is just around 4 Henry and then a Bridge that is 8 Henry (or vice versa).
Will the output level drastically differ?

Thanks

[roadtonever]

Apr 22, 2021 7:14:54 GMT -5 pablogilberto said:

Hey Gnuts!

I've been measuring PAF style pus and wanted to get your insights.
Based on my collected data, the Inductance of typical PAF is around 4 to 5 Henry.
But I do get a few which are as high as 8 Henry.

My question is, in your experience, what is the best electrical parameter value combination for a Neck and Bridge pickup to get a similar response and output level? Is it safe that both pickups should have a similar RLC values?

Is there good reason for having a Neck that is just around 4 Henry and then a Bridge that is 8 Henry (or vice versa).
Will the output level drastically differ?

Thanks

It depends on how you set the height of each position. In commercial sets with a hotter bridge I've seen everything from +40% to +100%. It also depends on if each position uses the same or different designs.

[antigua]

Apr 22, 2021 7:14:54 GMT -5 pablogilberto said:

Hey Gnuts!

I've been measuring PAF style pus and wanted to get your insights.
Based on my collected data, the Inductance of typical PAF is around 4 to 5 Henry.
But I do get a few which are as high as 8 Henry.

My question is, in your experience, what is the best electrical parameter value combination for a Neck and Bridge pickup to get a similar response and output level? Is it safe that both pickups should have a similar RLC values?

Is there good reason for having a Neck that is just around 4 Henry and then a Bridge that is 8 Henry (or vice versa).
Will the output level drastically differ?

Thanks

The distance between the pickups and the strings makes the biggest difference in the voltage output, and the distance-to-output ratio isn't linear, so there's probably multiple solutions on a curve. I know that 5 henries isn't enough to get volume parity with 4 henries, you would still have to set the bridge pickup closer to the strings to get the same voltage output. 8 henries, like a JB, can probably do it. I think the true benefit of the 5 henry bridge is just that it reduces the treble slightly, so that it sounds less harsh, and the distorted sound is a little smoother. 

[lowberg]

Hello everyone. Over the past year I've ventured into building my own guitar pickups, I found this thread and it was of great interest to me as naturally I would love to measure the frequency response of my pickups.

I decided to purchased the Velleman USB Oscilloscope, and give the tutorial in this thread a shot. Unfortunately I am not having success getting a reading. I will try to explain my steps, and would be hugely grateful if anyone could chime in and help me figure out where I went wrong...



I've never used a scope before but I was able to verify it's operational by hooking up the generator to channel 1 and playing around with the settings to get a reading.



When I followed the tutorial on page 1, I tried creating two driver coils to : one out of a humbucker bobbin with about 250 winds of 42awg magnet pickup wire, and one with the popsicle stick method. Both got a small resistance reading on my multimeter so pretty straight forward I don't think there's any issue there.


First I connected channel 2 and generator positive leads to exciter coil start wire, and the grounds of channel 2 and function generator to the finish of the coil wire



I then connected the single coil pickup to be tested connected to channel 1.




I set up the scope with the same settings as the original post





Then proceeded to Circuit Analyzer tab, made sure I had the same settings checked as well. Freq start 100hz, range 30khz, disable Log Freq steps,  made sure the proper audio view settings were correct ect.
When I ran the bode plot, nothing showed up. In the log it was showing a dBV of around -50 at every frequency range with a message like "Trace is below display area"



Lastly I noticed with Automatic Voltage scale enabled, it was instantly dropping V range to 0.1V, possibly a symptom of whatever issue I have with the configuration.
When I disable automatic voltage scale and run at 30V range, I do get a bode plot but it's a flat line more or less along the frequency spectrum.




Feeling pretty stumped after trying to follow the tutorial verbatim. I tried both versions of my driver coil, the bobbin and the popsicle stick with no success.

Any insight into where I may have gone wrong or might be missing, would be very appreciated!   

[antigua]

Jul 9, 2021 23:00:28 GMT -5 lowberg said:

Hello everyone. Over the past year I've ventured into building my own guitar pickups, I found this thread and it was of great interest to me as naturally I would love to measure the frequency response of my pickups.

I decided to purchased the Velleman USB Oscilloscope, and give the tutorial in this thread a shot. Unfortunately I am not having success getting a reading. I will try to explain my steps, and would be hugely grateful if anyone could chime in and help me figure out where I went wrong...

...

The amplitude setting in the main panel of the software shows 0.59Vpp, I think it can max out at 8Vpp, and I usually set mine to 4Vpp. 0.59Vpp might be too low.



Also I see you're using a probe with the function generator instead of a lead with alligator clips on the ends, I think that will work fine, but you'd have to make sure the probe is not set to 10x, because that adds a large series resistance to the probe. 

In your picture, the popsicle stick exciter is laid flat on the pickup, but you want the coil if the exciter to be along the same axis as the single coil, and when laying flat, it's perpendicular to the pickup coil. You'd want to clip off all of the stick below the coil, so that you can stand the stick upright over the pickup. 






For a humbucker, you'd lay it like this, so that the field intercepts both coils at once. If will give you a different reading if you treat it like a single coil, because the magnetic interaction will only involve one coil or the other. 



Any of these three things could plausibly cause the errors you're seeing. 

[lowberg]

Thank you so much! I spent the afternoon playing around and familiarizing with the Velleman and I actually found your other thread about the simplified version using a 1 meg resistor rather than exciter coil and was successful in plotting with that method! I will check my settings and try the exciter coil again tomorrow, my Velleman did not come with the alligator clip bcn lead, so likely the 10x setting on the generator probe is my main issue!

THANK YOU SO MUCH for the photos with the orientation for the popsicle stick method! You are a goldmine of info sir I will be busy reading all of your threads! 

[lowberg]

So thanks to antigua's help I was able to get up and running with the exciter coil method.

I was intrigued by phildefer's test with magnet strength changes from a few posts up so I decided to try the following:

I did a bode plot of a humbucker with a strong ceramic bar magnet (black line), and then removed the bar magnet completely with the pickup materials having barely any magnetic influence on the coil (maybe some very faint residual charge on the steel components, but wouldn't be functional in a guitar).... and got basically the same exact plot (blue line)





I was pretty surprised honestly. So would it be safe to say this method can't really give us much insight on the tonal effects the magnet type & charge contribute to in a pickup?

I would love to be able to get measurable data on that for example like swapping from a lower gauss Alnico 2 bar magnet to a stronger ceramic magnet in a humbucker. 

[antigua]

Jul 11, 2021 15:57:29 GMT -5 lowberg said:

So thanks to antigua's help I was able to get up and running with the exciter coil method.

I was intrigued by phildefer's test with magnet strength changes from a few posts up so I decided to try the following:

I did a bode plot of a humbucker with a strong ceramic bar magnet (black line), and then removed the bar magnet completely with the pickup materials having barely any magnetic influence on the coil (maybe some very faint residual charge on the steel components, but wouldn't be functional in a guitar).... and got basically the same exact plot (blue line)




I was pretty surprised honestly. So would it be safe to say this method can't really give us much insight on the tonal effects the magnet type & charge contribute to in a pickup?

I would love to be able to get measurable data on that for example like swapping from a lower gauss Alnico 2 bar magnet to a stronger ceramic magnet in a humbucker. 

The effects of the magnetic pull caused by a stronger or weaker magnets, upon the guitar strings, is not represented by this sort of test, but the magnet still is or is not a conductive or permeable metal part, so it still has an effect on the RLC properties of the pickup, and that can be seen with this test. The extent to which the magnet is conductive, it will lower the peak amplitude at the resonance, and the extent to which it's permeable, it will lower the resonant peak.

You won't see much difference from swapping a magnet in a humbucker, but you see a large difference with a Fender style single coil, since the magnets are in the core of the coil, where the coil's flux density is the highest. If you test humbucker magnet swaps with an LCR meter, like the DE-5000, you can see the the inductance of the pickup vary by around 30mH, and if you swap magnets in a Strat style pickup you can see the inductance vary by as much as 300mH, or 1 henry if you remove the magnets all together, or somehow found a ceramic pole piece (because ceramic magnets have no permeability). The 30mH variation with humbucker magnet swaps technically moves the resonant peak slightly, but the resolution of the Velleman plotter isn't high enough to show it clearly, so in that case I think it makes more sense to just consider the inductance readings from an LCR meter. With Fender style single coils, you can see the plot change by a lot. I made a plot like that here guitarnuts2.proboards.com/post/82822/thread

As for magnetic string pull effects, such as wolftones or vibration damping, that's distinct from the RLC properties of the pickup, and it's another kind of inquiry. I've tried raising and lowering pickups and seeing how it affected the string vibration with a spectrogram in another thread, and I can say that when the string pull increases, is causes the string movement to become more asymmetrical, which shifts the amplitude upwards, towards higher harmonics, in a very subtle way. In the same way that a pinch harmonic shifts amplitude to a higher harmonic, so to due magnetic string pull, but I haven't been able to detail which specific harmonics are increased based on the location and intensity of the string pull, because the effects are so subtle and hard to observe in the spectrogram. One take away though is that raising and lowering a pickup has the same general effect as a stronger or weaker magnet, because the difference is the same, string pull either increases or decreases. The upside of a weaker magnet is that you can set the pickup closer to the string, which improves magnetic reluctance and therefor output voltage, without also causing string pull.

[VT]

Sept 24, 2016 12:22:48 GMT -5 antigua said:

there is not a linear relationship between voltage and remnant flux density, but rather the voltage owes to the rate of flux change through the coil, as the string moves, and these two things don't have a linear relationship. Doubling the magnetic flux might only increase the voltage by about 15%, based on observational data.

Antigua, do you mean flux density on top of magnets/rods or flux measured on strings height? I thought that string itself becomes small magnet proportionally flux around.. But if string become twice stronger as magnet - it will produce double voltage in coil, no?
 

[antigua]

Aug 28, 2021 13:09:07 GMT -5 VT said:

Sept 24, 2016 12:22:48 GMT -5 antigua said:

there is not a linear relationship between voltage and remnant flux density, but rather the voltage owes to the rate of flux change through the coil, as the string moves, and these two things don't have a linear relationship. Doubling the magnetic flux might only increase the voltage by about 15%, based on observational data.

Antigua, do you mean flux density on top of magnets/rods or flux measured on strings height? I thought that string itself becomes small magnet proportionally flux around.. But if string become twice stronger as magnet - it will produce double voltage in coil, no?
 

Yeah, the magnetic strength of the pole pieces. I suppose if the flux in the strings doubled, the magnitude of flux change, and the induced voltage would also double, but the guitar string seems to be limited in how much flux it can obtain from the magnetized pole pieces. For example, if you hold a second magnet over the string and pole piece, having the same polarity, so that the sum of flux around the guitar string doubles (or more), and then you pluck the guitar string, the volume will not have doubled. The volume hardly changes at all. Either the string is magnetically saturating, or it's approaching saturation.

If you turn the magnet over, so that the poles are apposing, it neutralizes the magnetic flux to a large extent and the output becomes very quiet.  

[VT]

Hi,
antigua, you mean saturation? may be.. - strings core made from very special,  even uniq steel - with such tensile strength.. and not hardened in the same time.  But winding of wounded strings may be from any steel. Are you sure that second magnet will double magnetic flux on strings height on guitar and output increased just a bit? may be flux also was increased a bit? 
============
P.S. - designing low (this is restriction of guitar) profile pickup for own project.
Found this site. Found here "microcoil")) and a lots other. Very interesting place.   





 
 

[antigua]

Aug 30, 2021 5:32:19 GMT -5 VT said:

Hi,
antigua, you mean saturation? may be.. - strings core made from very special,  even uniq steel - with such tensile strength.. and not hardened in the same time.  But winding of wounded strings may be from any steel. Are you sure that second magnet will double magnetic flux on strings height on guitar and output increased just a bit? may be flux also was increased a bit? 
============
P.S. - designing low (this is restriction of guitar) profile pickup for own project.
Found this site. Found here "microcoil")) and a lots other. Very interesting place.   

If the guitar pickup had no magnet, or if the AlNiCo had no charge, the output level will be just as high (or very nearly) if you hold a magnet above the guitar string and the pickup. That goes to show that the magnetic field doesn't have to originate from the pickup, the field of flux just has to correctly intersect with the guitar string in order to magnetize it. So if the pickup is magnetized, and you hold a second magnet over the guitar strings, the sum of flux will roughly double (assuming the second magnet is similar to the pole piece and held at a similar distance from the string). I held a neodymium magnet over the guitar string, so the flux density around the guitar string will have more than doubled, but it didn't make the output noticeably louder than it already was.

You are correct in suggesting that if the magnetic field were twice as strong, that the output should double, since the amount of magnetic change through the coil would also double. Since that does not happen, this must mean that the guitar string is magnetically saturated. Even though the static magnetic field is much more dense, which is to say that it's much stronger, the moving magnetic field of the guitar string, which is what produces the voltage, is remaining the same. 

[VT]

I held a neodymium magnet over the guitar string, so the flux density around the guitar string will have more than doubled

 antigua, it looks like it is your  assumption that flux doubled  or more,  but I am i doubt.  did you mesured flux in moment?  unfortunatelly my education left somewhere in 198x and now I have some problems with theory.  so trials my way again(. ))
=================
P.S. I have handmade uncalibrated gaussmeter based on SS49 (about +-1000G). Now order simple bridges HG106C and will do a bit better tester for this my "hobby". I also have some handmade equipment to measure  pickup more or less to compare. result looks like:
docviewer.yandex.ru/view/7527192/?*=WyFM1DfPE%2Bk7%2FP%2FRmjxrRZThGW97InVybCI6InlhLWRpc2s6Ly8vZGlzay9GaXNobWFuIEZsdWVuY2Uv0JDQp9ClL1ZULCAgRmlzaG1hbiBGbHVlbmNlIFZvaWNlIDEgJiAyLCBGZW5kZXIgU0NOIG5lY2sucGRmIiwidGl0bGUiOiJWVCwgIEZpc2htYW4gRmx1ZW5jZSBWb2ljZSAxICYgMiwgRmVuZGVyIFNDTiBuZWNrLnBkZiIsIm5vaWZyYW1lIjpmYWxzZSwidWlkIjoiNzUyNzE5MiIsInRzIjoxNjMwMzgyNTUwMTIxLCJ5dSI6Ijk4MDQyODI3MTYyNzY0NTExNSJ9
but lots of questions about left.)

[antigua]

Aug 30, 2021 22:55:28 GMT -5 VT said:

I held a neodymium magnet over the guitar string, so the flux density around the guitar string will have more than doubled

 antigua, it looks like it is your  assumption that flux doubled  or more,  but I am i doubt.  did you mesured flux in moment?  unfortunatelly my education left somewhere in 198x and now I have some problems with theory.  so trials my way again(. ))
=================
P.S. I have handmade uncalibrated gaussmeter based on SS49 (about +-1000G). Now order simple bridges HG106C and will do a bit better tester for this my "hobby". I also have some handmade equipment to measure  pickup more or less to compare. result looks like:
docviewer.yandex.ru/view/7527192/?*=WyFM1DfPE%2Bk7%2FP%2FRmjxrRZThGW97InVybCI6InlhLWRpc2s6Ly8vZGlzay9GaXNobWFuIEZsdWVuY2Uv0JDQp9ClL1ZULCAgRmlzaG1hbiBGbHVlbmNlIFZvaWNlIDEgJiAyLCBGZW5kZXIgU0NOIG5lY2sucGRmIiwidGl0bGUiOiJWVCwgIEZpc2htYW4gRmx1ZW5jZSBWb2ljZSAxICYgMiwgRmVuZGVyIFNDTiBuZWNrLnBkZiIsIm5vaWZyYW1lIjpmYWxzZSwidWlkIjoiNzUyNzE5MiIsInRzIjoxNjMwMzgyNTUwMTIxLCJ5dSI6Ijk4MDQyODI3MTYyNzY0NTExNSJ9
but lots of questions about left.)

I have a gaussmeter, an WT10A, and I could place the probe beside the guitar string and see if the flux doubled, but I know it would, magnetic fields add together. The sum of flux at the location of the guitar string would include the flux from the existing magnet in the pickup, PLUS the external magnet held over the top of the pickup. If the steel string had a higher saturation point, then the string would become increasing magnetized, but that's not the case. In a sense, the pickup itself is acting as a "magnetic strength sensor" (as well as velocity), and by not producing a stronger output despite a more intense magnetic field (given the same velocity), it's apparent that the string is magnetically saturated. I might be missing something, but this seems self evident to me, since it can be observed through direct experimentation.   

Anecdotally, I've also degaussed AlNiCo 5 pole pieces, so that their flux drops from 1050G down to around 500G, and the result is a softer sound, but not a much quieter sound. I attribute the softer sound to the magnet not pulling as intensely on the guitar string. Magnetic pull on the guitar string causes asymmetric vibration, which promotes harmonics, and a harsher treble sound in turn. 

[VT]

Aug 31, 2021 1:26:00 GMT -5 antigua said:

The sum of flux at the location of the guitar string would include the flux from the existing magnet in the pickup, PLUS the external magnet held over the top of the pickup.

yes, you are right, superposition rule, my mistake. I just did not expect that saturation of string steel may have such dramatical effect. And if string core made from quite unig steel for 1st string - winding can be made from any..
And no need provide flux around string as much as possible but before 3rd or 6th string will produce wolftone..

  

[antigua]

Aug 31, 2021 5:53:37 GMT -5 VT said:

Aug 31, 2021 1:26:00 GMT -5 antigua said:

The sum of flux at the location of the guitar string would include the flux from the existing magnet in the pickup, PLUS the external magnet held over the top of the pickup.

yes, you are right, superposition rule, my mistake. I just did not expect that saturation of string steel may have such dramatical effect. And if string core made from quite unig steel for 1st string - winding can be made from any..
And no need provide flux around string as much as possible but before 3rd or 6th string will produce wolftone..

  

Yeah decades of experimentation has seems to suggest that there is an optimum flux that saturates the guitar string without causing excess pull, most have a measurement of 300 to 600 guass at the pole tops, except AlNiCo 5 Strat pickups measuring over 1000 gauss. Nevertheless a lot of people like the sound of the AlNiCo 5 Strat pickup, and I suspect that is' because the harsher sound (short of causing wolf tones) in that particular context has become familiar and appreciated after years of being heard on famous recordings. On the other hand, humbuckers with ceramic magnets have not been especially popular, and historically they've not been common in recordings, so there's no reason for people to feel accustomed to, or nostalgic over, that sound. Pickups involving neodymium magnets have also fell flat in the market. 

[ms]

Aug 31, 2021 11:48:51 GMT -5 antigua said:

Yeah decades of experimentation has seems to suggest that there is an optimum flux that saturates the guitar string without causing excess pull, most have a measurement of 300 to 600 guass at the pole tops, except AlNiCo 5 Strat pickups measuring over 1000 gauss. Nevertheless a lot of people like the sound of the AlNiCo 5 Strat pickup, and I suspect that is' because the harsher sound (short of causing wolf tones) in that particular context has become familiar and appreciated after years of being heard on famous recordings. On the other hand, humbuckers with ceramic magnets have not been especially popular, and historically they've not been common in recordings, so there's no reason for people to feel accustomed to, or nostalgic over, that sound. Pickups involving neodymium magnets have also fell flat in the market. 

So the string is saturated, or nearly so, from a field pointing along the string, resulting from the component of the field in that direction from the magnet. (A long thin piece of permeable material magnetizes much, much more easily along its axis than perpendicular to it.)  The sign of the axial field flips as you move from the neck side of the pole piece to the bridge side, since the field from the magnet points in opposite directions on the two sides.  This means that there is a transition region over the pole piece where the string is not saturated.  aquin observed that the pickup works the same if the magnet is below the string or rotated around 90 degrees so that the field comes from the side rather than below.  This means that the source of the field that makes the signal is the axial directed magnetization, which has the implied symmetry.  A significant component of the field from the string perpendicular to the axis (that is, that passes through the coil along its axis) occurs only where the magnetization changes rapidly with distance, that is, centered over the pole piece.

The length of the transition region should be an inverse function of the magnet field strength, but the strength of the field through the coil  should be a linear function.  The product of the two is roughly constant. Thus, I would expect that the output level of the pickup is nearly independent of the magnet field strength when it is strong enough to cause saturation except at  or near the pole piece.

[antigua]

Aug 31, 2021 13:08:36 GMT -5 ms said:

Aug 31, 2021 11:48:51 GMT -5 antigua said:

Yeah decades of experimentation has seems to suggest that there is an optimum flux that saturates the guitar string without causing excess pull, most have a measurement of 300 to 600 guass at the pole tops, except AlNiCo 5 Strat pickups measuring over 1000 gauss. Nevertheless a lot of people like the sound of the AlNiCo 5 Strat pickup, and I suspect that is' because the harsher sound (short of causing wolf tones) in that particular context has become familiar and appreciated after years of being heard on famous recordings. On the other hand, humbuckers with ceramic magnets have not been especially popular, and historically they've not been common in recordings, so there's no reason for people to feel accustomed to, or nostalgic over, that sound. Pickups involving neodymium magnets have also fell flat in the market. 

So the string is saturated, or nearly so, from a field pointing along the string, resulting from the component of the field in that direction from the magnet. (A long thin piece of permeable material magnetizes much, much more easily along its axis than perpendicular to it.)  The sign of the axial field flips as you move from the neck side of the pole piece to the bridge side, since the field from the magnet points in opposite directions on the two sides.  This means that there is a transition region over the pole piece where the string is not saturated.  aquin observed that the pickup works the same if the magnet is below the string or rotated around 90 degrees so that the field comes from the side rather than below.  This means that the source of the field that makes the signal is the axial directed magnetization, which has the implied symmetry.  A significant component of the field from the string perpendicular to the axis (that is, that passes through the coil along its axis) occurs only where the magnetization changes rapidly with distance, that is, centered over the pole piece.

The length of the transition region should be an inverse function of the magnet field strength, but the strength of the field through the coil  should be a linear function.  The product of the two is roughly constant. Thus, I would expect that the output level of the pickup is nearly independent of the magnet field strength when it is strong enough to cause saturation except at  or near the pole piece.

I agree that the magnetization of the string is modeled as perpendicular to the coil(s), and not co-axial, the fact that a permeable material supports itself better along it's axis is a good explanation for why that ends up being the case, but we agree that the guitar string is saturated, if you add more complimentary flux, and the output doesn't increase any further? 

It sounds like you might be saying that if you hold a magnet over the pickup, then the guitar string's magnetic exposure is more uniform, since it's always moving away from one magnet and towards another at the same points in time, but if the string is saturated, I take it to mean that this doesn't really matter. And then there's the hysteresis to consider, that even if the guitar string moves into a less magnetized point in space, that it still retains some fraction of the magnetic charge from when it was in the stronger magnetized point of space. 

Yet another experiment I've tried was putting those little tiny neodymiums buttons on top of the AlNiCo pole pieces, and again I didn't hear the volume increase much if at all, and that experiment comes about as close as possible to increasing the magnetic strength of the field in situ, without altering any other factors. I was surprised by how little difference it made, even to the overall tone. 

[gckelloch]

Very interesting stuff here. Yeah, the hysteresis of the strings probably nulls magnetic asymmetry (or whatever the correct term is) to a large extent. The vintage Fender pole stagger has the high E pole closer than the B, but would that really make any difference if the high E (being the most readily saturated string) is already saturated? Lowering the pole and raising the coil up a bit for the thinnest string makes more sense to me. Fender supposedly used a softer/weaker form of AlNiCo V in the early 60's so the poles could be cut without chipping. That's the "coveted" Fender SC sound, although kids today may have gotten used to the full strength AlNiCo V pole sound, tin ears...withstanding ;-). How Nd magnet powered pickups sound depends on the strength of the Nd magnet, the core mass and permeability, etc. Both Wilde and Zexcoil use Nd magnets along with various core alloys resulting in less string pull than AlNiCO V poles.

[antigua]

Aug 31, 2021 20:07:37 GMT -5 gckelloch said:

Very interesting stuff here. Yeah, the hysteresis of the strings probably nulls magnetic asymmetry (or whatever the correct term is) to a large extent. The vintage Fender pole stagger has the high E pole closer than the B, but would that really make any difference if the high E (being the most readily saturated string) is already saturated? Lowering the pole and raising the coil up a bit for the thinnest string makes more sense to me. Fender supposedly used a softer/weaker form of AlNiCo V in the early 60's so the poles could be cut without chipping. That's the "coveted" Fender SC sound, although kids today may have gotten used to the full strength AlNiCo V pole sound, tin ears...withstanding ;-). How Nd magnet powered pickups sound depends on the strength of the Nd magnet, the core mass and permeability, etc. Both Wilde and Zexcoil use Nd magnets along with various core alloys resulting in less string pull than AlNiCO V poles.

It's definitely most efficient to have the coil and the pole pieces at the same height. Fender's decision to make pole pieces stick far above the coil doesn't make much sense, but technical benefit gave way to nostalgia sometime in the 80's and 90's.

The main thing to consider, regardless of the magnet, is the permeability of the pole piece. If the pole has a higher permeability, it will transmit more magnetism from the strings down to the coil. Since the string is probably saturated, that permeability becomes very important, since it becomes the weakest link in the chain. AlNiCo 5 has a lower permeability than AlNiCo 2 or 3, therefore you can say that AlNiCo 2 or 3 pole pieces are more magnetically sensitive than AlNiCo 5, so the stagger will sound more dramatic with AlNiCo 2 or 3 than with AlNiCo 5. 

I'd never heard of Fender using a chip resistant form of AlNiCo 5, but the trend seems to be with AlNiCo, the higher the remnant flux (Br) the more brittle it is, so if it's true that they used a less brittle formulation, that it would have had a lower remanence and a higher permeability, something in between AlNCio 2 and AlNiCo 5.

[gckelloch]

Sept 2, 2021 13:10:39 GMT -5 antigua said:

Aug 31, 2021 20:07:37 GMT -5 gckelloch said:

Very interesting stuff here. Yeah, the hysteresis of the strings probably nulls magnetic asymmetry (or whatever the correct term is) to a large extent. The vintage Fender pole stagger has the high E pole closer than the B, but would that really make any difference if the high E (being the most readily saturated string) is already saturated? Lowering the pole and raising the coil up a bit for the thinnest string makes more sense to me. Fender supposedly used a softer/weaker form of AlNiCo V in the early 60's so the poles could be cut without chipping. That's the "coveted" Fender SC sound, although kids today may have gotten used to the full strength AlNiCo V pole sound, tin ears...withstanding ;-). How Nd magnet powered pickups sound depends on the strength of the Nd magnet, the core mass and permeability, etc. Both Wilde and Zexcoil use Nd magnets along with various core alloys resulting in less string pull than AlNiCO V poles.

It's definitely most efficient to have the coil and the pole pieces at the same height. Fender's decision to make pole pieces stick far above the coil doesn't make much sense, but technical benefit gave way to nostalgia sometime in the 80's and 90's.

The main thing to consider, regardless of the magnet, is the permeability of the pole piece. If the pole has a higher permeability, it will transmit more magnetism from the strings down to the coil. Since the string is probably saturated, that permeability becomes very important, since it becomes the weakest link in the chain. AlNiCo 5 has a lower permeability than AlNiCo 2 or 3, therefore you can say that AlNiCo 2 or 3 pole pieces are more magnetically sensitive than AlNiCo 5, so the stagger will sound more dramatic with AlNiCo 2 or 3 than with AlNiCo 5. 

I'd never heard of Fender using a chip resistant form of AlNiCo 5, but the trend seems to be with AlNiCo, the higher the remnant flux (Br) the more brittle it is, so if it's true that they used a less brittle formulation, that it would have had a lower remanence and a higher permeability, something in between AlNCio 2 and AlNiCo 5.

Yeah, I just learned about the efficiency benefit of permeability from the Zexcoil blog. I'd think it would also disproportionately increase fundamental strength and assymetry, but I dunno. That's a good point about it making a difference even when the string is saturated. John Suhr mentioned on Tonetalk that an old Fender employee told him about the softer/weaker AlNiCo V, and that the only reason the earlier poles where beveled was to remove the chips. My guess is it was just AlNiCO IV. It is more efficient to have the top of the poles at the same height as the coil, but Willi L Stich pointed out that the weaker/angled flux lines from the top edges of the pole can create some cancellations (and I believe it). A little above the coil produces a more true string sound.

[VT]

Sept 2, 2021 13:10:39 GMT -5 antigua said:

Fender's decision to make pole pieces stick far above the coil doesn't make much sense,

Winding of Strat coil is located under fiber bobbin flatwork and plastic cup of pickup, but Alnico rods can go up several millimeters higher then winding, by design. So why not use this possibility to increase level?

I'd never heard of Fender using a chip resistant form of AlNiCo 5

there was another alloy - CuNiFe - it allows even treaded rods. They say that its magnetic specs are close to AlNicCo2. Was used in   Fender Wide Range pickups

[antigua]

Sept 2, 2021 19:48:55 GMT -5 VT said:

Sept 2, 2021 13:10:39 GMT -5 antigua said:

Fender's decision to make pole pieces stick far above the coil doesn't make much sense,

Winding of Strat coil is located under fiber bobbin flatwork and plastic cup of pickup, but Alnico rods can go up several millimeters higher then winding, by design. So why not use this possibility to increase level?

The output level also depends on how close the coil is to the strings. Making the pole pieces taller means that the coil can't be raised as close to the strings as possible.

[VT]

Sept 2, 2021 22:35:07 GMT -5 antigua said:

The output level also depends on how close the coil is to the strings. Making the pole pieces taller means that the coil can't be raised as close to the strings as possible.

I mean in Strat pickup there are quite thick, looks like 3-4mm, fiber-airgap-plastic "sandwich" between copper wire and top surface of pickup. It could be reduced to ~1mm discarding decorate plastic cup and using bobbin made from polycarbonat instead of fiber. So coil could be 2-3mm closer to strings than it is, independent from pole pieces position.