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Post by antigua on Jan 5, 2017 17:01:37 GMT -5
That's very interesting, thanks. I didn't realize you also had worked picking position into it as well.
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Post by antigua on Jan 5, 2017 22:30:55 GMT -5
Yes indeed, and here is a "'fer instance": ... Someone on another forum was asking about voltage output, and it got me to thinking, is it possible to tell, for a Strat or Telecaster, what inductance value is required of a bridge pickup in order to match the output voltage of a neck pickup, due to the difference in displacement amplitudes? Say you have a typical 2.6H Strat neck pickup, and you want a bridge pickup that perfectly matches the output level. |
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Post by JohnH on Jan 5, 2017 23:07:05 GMT -5
Yes indeed, and here is a "'fer instance": ... Someone on another forum was asking about voltage output, and it got me to thinking, is it possible to tell, for a Strat or Telecaster, what inductance value is required of a bridge pickup in order to match the output voltage of a neck pickup, due to the difference in displacement amplitudes? Say you have a typical 2.6H Strat neck pickup, and you want a bridge pickup that perfectly matches the output level. What Ill do is take one pickup, maybe the Fat50 neck, and plot the output in the B and N positions, with all the modelling switched on. Each trace could be an envelope across all strings being strummed. Tben you can judge how many extra db's would be desirable for the bridge. Relating that to extra inductance would be a further step. |
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Post by JohnH on Jan 6, 2017 7:34:52 GMT -5
This is an envelope of the loudest harmonics at each frequency, for an equal SSL1 strummed across all strings, all strings open, in neck and bridge positions:  There is apparently about 8db of difference in the fundamentals, though the bridge PU has more energy in the high harmonics Here is it at fret 6:  The difference is a bit less. This is just string 1 E, showing envelopes and also individual harmonics (see key):  |
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Post by antigua on Jan 6, 2017 11:04:06 GMT -5
So, in general, would it be fair to say that you need enough of inductance increase in the bridge in order make the fundamental 6dB to 8dB greater?
It might be useful to some pickup winders out there (who appreciate this sort of thing) to have a calculator or a table that answers the question: if my neck pickup, and perhaps middle pickup, are inductance X, then what inductance is needed to make the bridge pickup roughly as loud at the fundamentals, to the nearest extent it can be approximated?
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Post by Charlie Honkmeister on Jan 6, 2017 12:42:39 GMT -5
(deleted) If I understood correctly, if, for example, I had a Strat and I were in the classical situation where I wanted that growly PAF tone at the bridge, but without going for a HSS pickguard, this thread should suggest that I definitely wouldn't find that exact tone if I only chose a single coil bridge pickup with the same resonant peak of that humbucker. It wouldn't be the same thing as installing a real PAF there, I mean, because of the different harmonics sensing. Now, I don't know how that angled bridge single coil translates as far as harmonics sensing, but I guess that's still different from a full size humbucker, because of the lack of comb filtering and narrow geometry of the single coil, isn't it? It is, but if you are talking about a full sized humbucker type loaded resonant frequency, a lot of the harmonic content differences are irrelevant because they are buried in the weeds above 3 KHz or so, because of the steep rolloff above resonance. Single coil sized bridge humbuckers can be very successful in a Strat. I remember the first one I put into a Strat -- a Seymour Duncan JB Junior. It had a really great lead voice under crunch and distortion - humbucker growl with just a little bit of squawk. Not identical to a Gibson Les Paul bridge HB crunch (your point) but hot, fluid, and expressive. The only problem (common) is that you could never get it to sound really "Strat single coil-like" either split or parallel coil, and as a result, in the notch position 2, the "quack" didn't sound right for cleaner playing in either HB or single coil mode, although it was fairly close with some height adjustments. Some folks on Harmony Central back in about 2002 or so were saying that the DiMarzio Fast Track 1 had a good single coil voice when split and good distortion tone when in HB series mode. Not to overly toot my own horn, but the variable resonant frequency tone control I have been working on was put in a Strat for the first demo. The bridge PU resonant frequency can be dialed from about 1.5 Khz to about 5 KHz - good HB midrange sound at one end of the pot, to super bright Strat/Tele sound at the other end of the control. I've written a post where you can duplicate this with just off the shelf parts including a commercial buffer module, and cheap Ebay Chinese single coil sized humbucker rail pickups that go for about $8.50 each. |
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Post by Charlie Honkmeister on Jan 6, 2017 13:29:46 GMT -5
And it quacks like a duck on crystal meth.  |
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Post by Charlie Honkmeister on Jan 6, 2017 13:44:37 GMT -5
So, in general, would it be fair to say that you need enough of inductance increase in the bridge in order make the fundamental 6dB to 8dB greater? It might be useful to some pickup winders out there (who appreciate this sort of thing) to have a calculator or a table that answers the question: if my neck pickup, and perhaps middle pickup, are inductance X, then what inductance is needed to make the bridge pickup roughly as loud at the fundamentals, to the nearest extent it can be approximated? Only problem with that is, that if you want to maintain the "same" tonality and increase the inductance to get more output for the bridge, you also have to decrease the capacitive part of the RC load, on a per-pickup basis. This is surely doable, but is starting to argue for onboard buffering the instrument, and then doing anything we want for RC loading, including custom loading per pickup, before the high-Z buffer, and getting rid of dependency on cable capacitance. |
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Post by antigua on Jan 6, 2017 15:09:09 GMT -5
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Post by JohnH on Jan 6, 2017 19:21:27 GMT -5
So, in general, would it be fair to say that you need enough of inductance increase in the bridge in order make the fundamental 6dB to 8dB greater? It might be useful to some pickup winders out there (who appreciate this sort of thing) to have a calculator or a table that answers the question: if my neck pickup, and perhaps middle pickup, are inductance X, then what inductance is needed to make the bridge pickup roughly as loud at the fundamentals, to the nearest extent it can be approximated? Although that is what numbers would suggest, Id expect that most players would find that to be too much if they were wanting a subjective volume balance across the set. The bridge, although lower in the fundamental, is a couple of db higher across the upper harmonics. Also, I think a B pickup can be set higher than a neck one. My guess would be about 3db would be enough of a correction. I have an HSS Strat, and I like that the bridge is definitely louder. But measuring it as carefully as I can by trying to record consistent strums, it is about 6db more than the neck, suggesting that 6db is more than required just to match volumes. |
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Post by antigua on Jan 15, 2017 14:36:01 GMT -5
We were talking about pickup distance, which related to magnetic field width, on another forum. I'm posting a summary here of what was discussed in order to combine all the observations together in this thread. The fun starts here. This looks to me like theoretical and observational confirmation that a more dispersed magnetic field, a consequence of distance in this particular case, results in a roll off of harmonics that doesn't become real audible until the 4th or 5th harmonic, but of course the specific harmonic and comb filtering depends on the position of the pickup, the distance, the pitch of the string, etc. Below is a cut an paste of the practical results and the theoretical correlation: I think you're seeing the effect of a more distributed window. You see the same thing with Tillman's harmonic amplitude calculator www.till.com/articles/PickupResponseDemo/index.htmlIt appears that, in general, the wider the window, the more the harmonics cancel themselves out. The same thing should happen when using magnets of lower flux density, such as AlNiCo 2 or 3, because like a magnet that is further away from the strings, having less flux for a given geometry of magnet will result in a more evenly distributed magnetic field. This is in contrast to having a smaller magnet with the same flux density, like if you were to make a tiny AlNiCo 5 magnet, for example. Here is the harmonic makeup with 0.5" distance:  Now here it is with 1"  Here is an overlap of the two, for easier viewing:  If we take things to the extreme and pretend the pickup was like a foot or two away from the string, it might look like this:  And here's a razor thin pickup:  |
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Post by ms on Jan 15, 2017 17:40:56 GMT -5
"The same thing should happen when using magnets of lower flux density, such as AlNiCo 2 or 3, because like a magnet that is further away from the strings, having less flux for a given geometry of magnet will result in a more evenly distributed magnetic field. This is in contrast to having a smaller magnet with the same flux density, like if you were to make a tiny AlNiCo 5 magnet, for example." --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- I don't think so. Think of the magnet as made up of a huge number of very small identical magnets. Their distribution determines the geometry of the field. To make the magnet weaker, make each of the tiny magnets weaker by the same amount. The geometry of the field stays the same; all that changes is the strength. |
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Post by antigua on Jan 15, 2017 19:11:35 GMT -5
I don't think so. Think of the magnet as made up of a huge number of very small identical magnets. Their distribution determines the geometry of the field. To make the magnet weaker, make each of the tiny magnets weaker by the same amount. The geometry of the field stays the same; all that changes is the strength. Is it possible instead that a weaker pole piece magnetically charges the steel guitar string more evenly over a greater width, due to the BH curve of the steel string ?
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Post by ms on Jan 16, 2017 6:35:49 GMT -5
Is it possible instead that a weaker pole piece magnetically charges the steel guitar string more evenly over a greater width, due to the BH curve of the steel string ?
I think the magnetization of the string is not strong enough to move to a different slope on the curve. Maybe this is not a real effect, but results from not adjusting the volume back to the same level with the weaker magnets. |
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Post by antigua on Jan 16, 2017 14:36:55 GMT -5
Is it possible instead that a weaker pole piece magnetically charges the steel guitar string more evenly over a greater width, due to the BH curve of the steel string ?
I think the magnetization of the string is not strong enough to move to a different slope on the curve. Maybe this is not a real effect, but results from not adjusting the volume back to the same level with the weaker magnets. Are you suggesting then that the magnetization of the steel string has an effectively linear relationship with the magnetic moment that intersects it? In other words, that the steel string is a linear reflection of the magnetization imposed upon it? That just doesn't seem right to me for some reason. Do you happen to know how much H it would take to max out the B of the steel? AlNiCo 5 is somewhat strong in close proximity. Is it safe to assume that it's too weak to saturate the steel string? I think it's a question worth asking, though I don't think the answer would necessarily validate the observations in this case. --- There are some Seymour Duncan pickups that are virtually the same, aside from one set using AlNiCo 2, and another using AlNiCo 5. The AlNiCo 2 produces a higher inductance, but I think the observed difference goes beyond overall amplitude. This can be tested, but it will have to wait until someone can fashion two pickups with either magnet and ensure that the inductance and resonance are equivalent. I did find that a couple of my pickup sets had similar inductance and resonance, but different magnets, A5 vs A3, and they were both in separated guitars. I compared how they sounded. I went back and forth between them, and I observed the usual differences you see people say about them, the AlNiCo 5 having a seemingly more prominent treble and bass. I don't like to trade in vague perceptions, but it motivates me to find an whole explanation for the difference. |
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Post by ms on Jan 16, 2017 16:17:31 GMT -5
I think the magnetization of the string is not strong enough to move to a different slope on the curve. Maybe this is not a real effect, but results from not adjusting the volume back to the same level with the weaker magnets. Are you suggesting then that the magnetization of the steel string has an effectively linear relationship with the magnetic moment that intersects it? In other words, that the steel string is a linear reflection of the magnetization imposed upon it? That just doesn't seem right to me for some reason. Do you happen to know how much H it would take to max out the B of the steel? AlNiCo 5 is somewhat strong in close proximity. Is it safe to assume that it's too weak to saturate the steel string? I think it's a question worth asking, though I don't think the answer would necessarily validate the observations in this case. --- There are some Seymour Duncan pickups that are virtually the same, aside from one set using AlNiCo 2, and another using AlNiCo 5. The AlNiCo 2 produces a higher inductance, but I think the observed difference goes beyond overall amplitude. This can be tested, but it will have to wait until someone can fashion two pickups with either magnet and ensure that the inductance and resonance are equivalent. I did find that a couple of my pickup sets had similar inductance and resonance, but different magnets, A5 vs A3, and they were both in separated guitars. I compared how they sounded. I went back and forth between them, and I observed the usual differences you see people say about them, the AlNiCo 5 having a seemingly more prominent treble and bass. I don't like to trade in vague perceptions, but it motivates me to find an whole explanation for the difference. Saturating steel usually requires a closed magnetic circuit, that is, one in which the flux completes a loop with high permeability material. It is easy to change magnets in hum buckers. If you do not want the effect of the steel for this test, then use ferrite for the pole pieces. |
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Post by antigua on Jan 16, 2017 16:22:03 GMT -5
It's true that humbuckers can have their magnets swapped with ease, but that would also impact the inductance and damping values a bit, which just taints the test results, but now that you mention steel poles pickups, it occurs to me that I could use neodymium buttons to alter the flux density of a ceramic/steel pickup without altering the reactance at all. I'll move this higher up in my long to do list.
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Post by ms on Jan 16, 2017 18:36:21 GMT -5
It's true that humbuckers can have their magnets swapped with ease, but that would also impact the inductance and damping values a bit, which just taints the test results, but now that you mention steel poles pickups, it occurs to me that I could use neodymium buttons to alter the flux density of a ceramic/steel pickup without altering the reactance at all. I'll move this higher up in my long to do list. Sounds like a good plan. Yes, the magnet in a hum bucker affects things. Here are impedance plots of an SD SH1N with and without the magnet. The other thing that can happen is that a stronger field alters how the string vibrates due to the magnetic force. Not sure this is really what people mean when they say that different kinds of magnets sound different.  Attachments:
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Post by ms on Jan 17, 2017 19:04:29 GMT -5
So I measured the impedance with A5 and A3. The results are here:   There is not a lot of difference. The differences in magnitude are 100Hz: .05db, 1000Hz: .15 db, 5000Hz: .12 db, at peak: .06 db I do not think that factors relating to the impedance (conductivity, permeability) from the two magnets are audible. That leaves differences from field strength. |
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Post by antigua on Jan 17, 2017 19:29:23 GMT -5
So I measured the impedance with A5 and A3. The results are here: There is not a lot of difference. The differences in magnitude are 100Hz: .05db, 1000Hz: .15 db, 5000Hz: .12 db, at peak: .06 db I do not think that factors relating to the impedance (conductivity, permeability) from the two magnets are audible. That leaves differences from field strength. That's good data. I just wanted to rule it out completely. Speaking of small differences, I've seen it suggested that, say a 0.5 dB difference, usually not audible, might be audible with gain, due to the non linear transfer function. I don't know enough about it to confirm or deny that, but if true, it would add some eliminating the variable completely. |
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Post by antigua on Feb 7, 2017 13:10:27 GMT -5
Earlier I was getting hung up on how having the magnets closer of farther from the string might make the "view" of the string wider. I've seen some people say that a stronger magnet is a more focused one, but others have said that the focus, or the shape of the magnetic field, is the same regardless of how strong the magnet is. According to FEM, the shape is the same no matter the strength.
So it gets me to thinking that when you raise of lower a pickup, the important difference might not be the proximity between the magnet and the string, but rather the proximity between the coil(s) and the string. A greater distance between the string and coil should increase the sensing width, for the same reason that when you stand further away from something, you see more of it. But then again, eyesight and magnetic lines don't follow the same rules, so I'm not sure if the analogy holds water.
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Post by wgen on Feb 28, 2017 13:29:28 GMT -5
Hello,
I'm writing here again because I was toying with the Tillman guitar pickup response demonstration, when I started thinking about one thing;
when I'm simulating a full size humbucker, shouldn't I select two pickups of 1 inch of width, instead of a single pickup of 2.5 inches? Shouldn't I put the two pickup apertures closer together, with one a little above the other?
I was thinking that both the coils of a humbucker are sensing the string harmonics, so I thought about this.
Hope that was clear enough, thank you very much!
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Post by antigua on Feb 28, 2017 14:08:30 GMT -5
Hello, I'm writing here again because I was toying with the Tillman guitar pickup response demonstration, when I started thinking about one thing; when I'm simulating a full size humbucker, shouldn't I select two pickups of 1 inch of width, instead of a single pickup of 2.5 inches? Shouldn't I put the two pickup apertures closer together, with one a little above the other? I was thinking that both the coils of a humbucker are sensing the string harmonics, so I thought about this. Hope that was clear enough, thank you very much! You're right, two side by side pickups would be a better approximation, but it doesn't really matter, because the distinction only effects higher frequencies. If the difference is above 4kHz, you're not really going to hear it, and if it's over 5kHz, you definitely won't hear it, because electric guitar specific speakers suppress frequencies above that point. The comb filtering of one pickup, or of two smaller pickups, doesn't become readily audible until they're a few inches wide, or a few inches apart, then you see scooping in the 1 to 3 kHz range, where the comb filtering will really start to color the tone. IMO, 2.5 inches is too wide of an aperture for a humbucker model. The pickup itself is only 1.44" wide overall, and the sensing width is mostly related to the pole piece. The flux is highly concentrated in the string over the pole piece, and past that point it becomes "return path" flux, which actually serves to cancel out the primary flux, to a small degree. The segment of string that shares polarity with the pole pieces depends on how far away the string is from the pole piece, further = wider. The string also moves nearer and further when plucked, so it becomes sort of an average distance, but for every moment it's further from the pole piece, there's likely an equal moment when the string is closer to the pole piece, so it's a wash. |
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Post by wgen on Feb 28, 2017 20:23:30 GMT -5
Thanks a lot man! I was now thinking if, because of the fact that "the sensing width is mostly related to the pole piece. The flux is highly concentrated in the string over the pole piece, and past that point it becomes "return path" flux, which actually serves to cancel out the primary flux, to a small degree", I would better select a pickup width of 0.25 of an inch only, which would, maybe, better approximate the pole pieces.
But, I was thinking also if there is some flux around the coil, too, so that the typical compression effect of overdrives and tube amplifiers, even when mostly clean, would somehow sort out the difference of harmonics sensing between the pole pieces width and the coil width, making the 1 inch reference a more appropriate selection for a single coil in the Tillman model.
Don't know if this doubt is clear enough, it's just that I was imaging a situation where you have this ceiling at the top, which would be represented by the limit of the tube amp/pedal that are compressing the signal...this limit is immediately reached by the harmonics just above the pole pieces, but then, it is also touched by the "other" harmonics, because, even if these are lower in output volume in respect to the ones just above the pole pieces, they would reach that ceiling, anyway.
I don't know if this makes sense, but I was imaging a situation similar to the forward voltage drop of the clipping diodes in a Tube Screamer, which is around 600 mV, so that, no matter how loud your signal is, it would be chopped off at 600 mV max anyway. This pedal would squash a high output humbucker monster just like a lower output single coil, so that they would both be reduced at that same level of max output voltage of 600 mV. Of course the high output humbucker would be compressed more, but I was mainly interested in the transient peak only here.
So, I was thinking if the harmonics sensing, even if this is certainly not equal for all the surface of a pickup itself, but perhaps it is "homogenized" at the subsequent stages of a signal chain.
I really don't know if this reference applies here.
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Post by antigua on Feb 28, 2017 23:49:01 GMT -5
Thanks a lot man! I was now thinking if, because of the fact that "the sensing width is mostly related to the pole piece. The flux is highly concentrated in the string over the pole piece, and past that point it becomes "return path" flux, which actually serves to cancel out the primary flux, to a small degree", I would better select a pickup width of 0.25 of an inch only, which would, maybe, better approximate the pole pieces. But, I was thinking also if there is some flux around the coil, too, so that the typical compression effect of overdrives and tube amplifiers, even when mostly clean, would somehow sort out the difference of harmonics sensing between the pole pieces width and the coil width, making the 1 inch reference a more appropriate selection for a single coil in the Tillman model. I'm not sure what you mean entirely. It doesn't matter too much, because you won't see a meaningful difference by adding or removing half an inch in the audible realm, below 5kHz. Here's a pic I took with some magnet film, it only costs about $15 for a 4x6" piece. As far as comb filtering is concerned, they all might as well be the same width. Aperture is like focus; the smaller the aperture, the tinier the harmonic that is visible, but there comes a point where the harmonic is so high, that you can't hear it anyway. It's like having a 50 megapixel camera that is higher resolution than your eyes could ever make out. In the Tillman demo, everything beyond 5kHz is academic.  Don't know if this doubt is clear enough, it's just that I was imaging a situation where you have this ceiling at the top, which would be represented by the limit of the tube amp/pedal that are compressing the signal...this limit is immediately reached by the harmonics just above the pole pieces, but then, it is also touched by the "other" harmonics, because, even if these are lower in output volume in respect to the ones just above the pole pieces, they would reach that ceiling, anyway. I don't know if this makes sense, but I was imaging a situation similar to the forward voltage drop of the clipping diodes in a Tube Screamer, which is around 600 mV, so that, no matter how loud your signal is, it would be chopped off at 600 mV max anyway. This pedal would squash a high output humbucker monster just like a lower output single coil, so that they would both be reduced at that same level of max output voltage of 600 mV. Of course the high output humbucker would be compressed more, but I was mainly interested in the transient peak only here. So, I was thinking if the harmonics sensing, even if this is certainly not equal for all the surface of a pickup itself, but perhaps it is "homogenized" at the subsequent stages of a signal chain. I really don't know if this reference applies here. I understand what you mean. It's hard to visualize exactly what the magnetic field of the guitar string looks like, and how it changes as the string moves, and how it does or does not induce flux change through the coil, so it's tough, maybe impossible to answer the question, whether distinction brings out harmonics that are at the far reaches of the aperture. One experiment you can try, if you have a spare single coil, is hook the coil up to an amp by itself, and then hold it over guitar strings, and see how the amplitude and sound changes when the pickup is beside the strings, versus over the strings, with distortion and without. You might be able to intuit an answer. |
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Post by wgen on Mar 1, 2017 4:55:28 GMT -5
I'm not sure what you mean entirely. It doesn't matter too much, because you won't see a meaningful difference by adding or removing half an inch in the audible realm, below 5kHz. Here's a pic I took with some magnet film, it only costs about $15 for a 4x6" piece. As far as comb filtering is concerned, they all might as well be the same width. Aperture is like focus; the smaller the aperture, the tinier the harmonic that is visible, but there comes a point where the harmonic is so high, that you can't hear it anyway. It's like having a 50 megapixel camera that is higher resolution than your eyes could ever make out. In the Tillman demo, everything beyond 5kHz is academic. I understand what you mean. It's hard to visualize exactly what the magnetic field of the guitar string looks like, and how it changes as the string moves, and how it does or does not induce flux change through the coil, so it's tough, maybe impossible to answer the question, whether distinction brings out harmonics that are at the far reaches of the aperture. One experiment you can try, if you have a spare single coil, is hook the coil up to an amp by itself, and then hold it over guitar strings, and see how the amplitude and sound changes when the pickup is beside the strings, versus over the strings, with distortion and without. You might be able to intuit an answer. Thank you very much man, very helpful! I guess that when it comes to the magnetic field it all becomes pretty bizarre. However, I remember that once we already talked about strings being more or less firm at the pick and the relative harmonics...I guess that now I understand that a higher gauge string will have more overall tension, so the harmonics at the far reach of the aperture will be less than with a more "flabby" string, because the high gauge string will stay more firm, "in the window" of the pole piece. Is it correct? A light gauge string will move more so it will have more of that "return path" flux which will cancel some more primary harmonics. |
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