timtam
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Post by timtam on Jan 21, 2022 0:09:00 GMT -5
I don't keep a close eye on pickup manufacturers' websites. But other than seeing inductance quoted somewhat more often these days, and the occasional near-meaningless bar chart showing treble/mids/highs, I don't recall seeing any pickup manufacturers publishing bode plots before. So I was pleasantly surprised to come across one small UK winder who started putting bode plots (without integration) on his Facebook page recently:
And he's just started them putting them on his product website, at least for his own single coil winds so far: www.axesrus.co.uk/ARUL60sSC-p/late60s-uk-sc-set.htmLook under the "More Tech Stuff" tab. It's difficult to compare them as is (more comparisons on his FB). Are there any other manufacturers publishing bode plots ? |
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Post by gckelloch on Jan 21, 2022 2:49:36 GMT -5
You can find some examples of Bode plots plus a lot more relevant & accurate information from Dr. Scott Lawing on the Zexcoil site. FI, the magnetized string doesn't so much "excite" the magnetic field around the pickup as the flux lines coming from it simply oscillate through the coil. It's also not the sharper peak (higher Q) of AlNiCo V that makes it sound more snappy/brighter than AlNiCo II, III or IV, but the effect on the string harmonics from the stronger pull combined with how the lower permeability doesn't attract the flux lines as much into the coil. Scott covers all that and more in his Blog. Worth reading if you want the real story.
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Post by antigua on Jan 21, 2022 12:36:38 GMT -5
It's good to see, but also unnecessary to some extent. If you wind PAF replicas, for example, and the only thing that varies from one to the next is the amount of wire and the magnet type (and that's the business model for dozens of sole proprietors making and selling pickups) , the bode plot will look nearly identical for all of them, because so much of the plot line owes to the eddy currents, and if you're using a PAF platform for all your pickups, then the eddy currents are about the same in all cases. The same goes with making Fender style pickups.
The bode plot would make most sense if you were making a new kind of noise cancelling pickup, or a new Gretsch style pickup, and you wanted to demonstrate that the new pickup design wasn't weighed down by eddy currents, or that the design otherwise resulted in an interesting response curve. TV Jones would be a good one to have bode plots for, because they have such a wide variety of pickup constructions. It's also good to plot various "noise cancelling" pickups, because sometimes the noise cancelling parts result in a lower Q factor, and it's good to be aware, you can use 500k pots instead of 250k, or 1med instead of 500k if you know the pickup is lossy before-hand. Sometimes the manufacturers will say to use 250k or 500k pots, just so that the customer won't be scared away by the prospect of having to change out all the control pots in the guitar.
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Post by ms on Jan 22, 2022 5:56:54 GMT -5
You can find some examples of Bode plots plus a lot more relevant & accurate information from Dr. Scott Lawing on the Zexcoil site. FI, the magnetized string doesn't so much "excite" the magnetic field around the pickup as the flux lines coming from it simply oscillate through the coil. It's also not the sharper peak (higher Q) of AlNiCo V that makes it sound more snappy/brighter than AlNiCo II, III or IV, but the effect on the string harmonics from the stronger pull combined with how the lower permeability doesn't attract the flux lines as much into the coil. Scott covers all that and more in his Blog. Worth reading if you want the real story. Are you sure you have all that right? There is no doubt that a higher Q gives a brighter sound. I am not saying that a stronger field does not have do it, too by increasing harmonics. Lower permeability can lead to a brighter sound by lowering inductance and raising the resonant frequency. |
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Post by gckelloch on Jan 22, 2022 6:53:56 GMT -5
You can find some examples of Bode plots plus a lot more relevant & accurate information from Dr. Scott Lawing on the Zexcoil site. FI, the magnetized string doesn't so much "excite" the magnetic field around the pickup as the flux lines coming from it simply oscillate through the coil. It's also not the sharper peak (higher Q) of AlNiCo V that makes it sound more snappy/brighter than AlNiCo II, III or IV, but the effect on the string harmonics from the stronger pull combined with how the lower permeability doesn't attract the flux lines as much into the coil. Scott covers all that and more in his Blog. Worth reading if you want the real story. Are you sure you have all that right? There is no doubt that a higher Q gives a brighter sound. I am not saying that a stronger field does not have do it, too by increasing harmonics. Lower permeability can lead to a brighter sound by lowering inductance and raising the resonant frequency. The Q makes much less difference when the total resistance on the pickup is factored in. There may then be less than 1dB difference in the peak of a coil going from A5 to A3, but less than half the Gauss has a big affect on how string pull affects the harmonics and how the attack hits the amp input stage. The higher permeability of A3 would only slightly increase inductance, but the affect of drawing the string flux lines down more into the coil is likely what increases lower harmonic strength. It should be akin to raising the coil closer to the string in a respect. I don't know if anyone has a definitive answer on that. I'd ask Scott. |
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Post by ms on Jan 22, 2022 7:17:19 GMT -5
Are you sure you have all that right? There is no doubt that a higher Q gives a brighter sound. I am not saying that a stronger field does not have do it, too by increasing harmonics. Lower permeability can lead to a brighter sound by lowering inductance and raising the resonant frequency. The Q makes much less difference when the total resistance on the pickup is factored in. There may then be less than 1dB difference in the peak of a coil going from A5 to A3, but less than half the Gauss has a big affect on how string pull affects the harmonics and how the attack hits the amp input stage. The higher permeability of A3 would only slightly increase inductance, but the affect of drawing the string flux lines down more into the coil is likely what increases lower harmonic strength. It should be akin to raising the coil closer to the string in a respect. I don't know if anyone has a definitive answer on that. I'd ask Scott. I am confused. If there is a significant difference in Q, you hear it. But why should there be very much difference in Q between A5 and A3? It is the conductivity of the material that matters for the Q, and I suspect that it is not all that different. I do not understand how drawing flux lines into the coil increases lower harmonic strength. Why should it have any effect on the frequency response? |
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Post by gckelloch on Jan 22, 2022 8:58:01 GMT -5
The Q makes much less difference when the total resistance on the pickup is factored in. There may then be less than 1dB difference in the peak of a coil going from A5 to A3, but less than half the Gauss has a big affect on how string pull affects the harmonics and how the attack hits the amp input stage. The higher permeability of A3 would only slightly increase inductance, but the affect of drawing the string flux lines down more into the coil is likely what increases lower harmonic strength. It should be akin to raising the coil closer to the string in a respect. I don't know if anyone has a definitive answer on that. I'd ask Scott. I am confused. If there is a significant difference in Q, you hear it. But why should there be very much difference in Q between A5 and A3? It is the conductivity of the material that matters for the Q, and I suspect that it is not all that different. I do not understand how drawing flux lines into the coil increases lower harmonic strength. Why should it have any effect on the frequency response? I think the Q of a coil is a bit lower with A2 or A3 than A5, but I don't know if permeability or Gauss is the cause. Again, the relative difference in the resonance peak is much less after it's damped by the total resistance load. It's not the freq response, but the relative difference of the stronger vs weaker string vibrations for each note that is accentuated by coil proximity. I'm speculating that roughly the same thing happens when the flux lines are pulled deeper into the coil, but it might just increase overall output for a given Gauss level. Scott Lawing might know a definitive answer. |
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Post by ms on Jan 22, 2022 9:51:33 GMT -5
I am confused. If there is a significant difference in Q, you hear it. But why should there be very much difference in Q between A5 and A3? It is the conductivity of the material that matters for the Q, and I suspect that it is not all that different. I do not understand how drawing flux lines into the coil increases lower harmonic strength. Why should it have any effect on the frequency response? I think the Q of a coil is a bit lower with A2 or A3 than A5, but I don't know if permeability or Gauss is the cause. Again, the relative difference in the resonance peak is much less after it's damped by the total resistance load. It's not the freq response, but the relative difference of the stronger vs weaker string vibrations for each note that is accentuated by coil proximity. I'm speculating that roughly the same thing happens when the flux lines are pulled deeper into the coil, but it might just increase overall output for a given Gauss level. Scott Lawing might know a definitive answer. The strength of the magnetic field affects the operating point on the hysteresis curve, and thus the permeability, and therefore the inductance and the resonant frequency. The Q is a function of the losses in the resonant circuit, and one factor in that is the conductivity of the pole material. But the Q has little to do directly with the permeability or the strength of the permanent field. Yes, the strength of the permanent field affects the relative levels of the string harmonics, and thus the frequency response of the instrument. (Here I am using "frequency response" in a more general way than just the response of the electronic filter made by the pickup circuit. Sorry if that is confusing.) More flux from the vibrating string through the core does not do that. (I do not think that Scott Lawing can give you a more definitive answer.) A stronger magnetic field affects how the string vibrates; that is the source of the change in harmonics. There is no analogous effect in the core. |
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timtam
Meter Reader 1st Class
Posts: 53
Likes: 24
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Post by timtam on Jan 22, 2022 9:58:50 GMT -5
It's good to see, but also unnecessary to some extent. If you wind PAF replicas, for example, and the only thing that varies from one to the next is the amount of wire and the magnet type (and that's the business model for dozens of sole proprietors making and selling pickups) , the bode plot will look nearly identical for all of them, because so much of the plot line owes to the eddy currents, and if you're using a PAF platform for all your pickups, then the eddy currents are about the same in all cases. The same goes with making Fender style pickups. I think it's a necessary step towards the buying public better understanding all pickups. If you're saying that most PAF replicas are sonically similar, then that's not something that your average pickup-buying Joe knows. So if seeing similar bode plots at least raises that possibility in their mind - if standardized plots became more commonly published - and buyers thus approached buying a supposedly "better" PAF with a bigger grain of scepticism, then that's a good thing I think. But the pickup companies might lose sales by fewer unnecessary purchases that way, if some of the smoke and mirrors they use to distinguish between their products and their competitors' was replaced by something more objective. So bode plots are probably not something that most are going to publish voluntarily (assuming some?/most? measure them internally). Buyers will need to demand bode plots from them. Incidentally the axesrus guy did a FB post on PAFs recently, making a distinction between the vintage-correct parts and the much smaller number of things that actually makes them sound vintage. He seems to approach the whole industry with a good dose of scepticism. |
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Post by gckelloch on Jan 22, 2022 11:31:13 GMT -5
I think the Q of a coil is a bit lower with A2 or A3 than A5, but I don't know if permeability or Gauss is the cause. Again, the relative difference in the resonance peak is much less after it's damped by the total resistance load. It's not the freq response, but the relative difference of the stronger vs weaker string vibrations for each note that is accentuated by coil proximity. I'm speculating that roughly the same thing happens when the flux lines are pulled deeper into the coil, but it might just increase overall output for a given Gauss level. Scott Lawing might know a definitive answer. The strength of the magnetic field affects the operating point on the hysteresis curve, and thus the permeability, and therefore the inductance and the resonant frequency. The Q is a function of the losses in the resonant circuit, and one factor in that is the conductivity of the pole material. But the Q has little to do directly with the permeability or the strength of the permanent field. Yes, the strength of the permanent field affects the relative levels of the string harmonics, and thus the frequency response of the instrument. (Here I am using "frequency response" in a more general way than just the response of the electronic filter made by the pickup circuit. Sorry if that is confusing.) More flux from the vibrating string through the core does not do that. (I do not think that Scott Lawing can give you a more definitive answer.) A stronger magnetic field affects how the string vibrates; that is the source of the change in harmonics. There is no analogous effect in the core. Check out his blog on pickup function. He specifically models the string flux line paths of an A5 vs higher permeability pole. There will simply be more V If more of the lines from the string pass though more of the coil. How is that controversial? I can't say if that will increase stronger vibrations more than weaker ones, but it seems like it might. |
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Post by ms on Jan 22, 2022 12:04:25 GMT -5
The strength of the magnetic field affects the operating point on the hysteresis curve, and thus the permeability, and therefore the inductance and the resonant frequency. The Q is a function of the losses in the resonant circuit, and one factor in that is the conductivity of the pole material. But the Q has little to do directly with the permeability or the strength of the permanent field. Yes, the strength of the permanent field affects the relative levels of the string harmonics, and thus the frequency response of the instrument. (Here I am using "frequency response" in a more general way than just the response of the electronic filter made by the pickup circuit. Sorry if that is confusing.) More flux from the vibrating string through the core does not do that. (I do not think that Scott Lawing can give you a more definitive answer.) A stronger magnetic field affects how the string vibrates; that is the source of the change in harmonics. There is no analogous effect in the core. Check out his blog on pickup function. He specifically models the string flux line paths of an A5 vs higher permeability pole. There will simply be more V If more of the lines from the string pass though more of the coil. How is that controversial? I can't say if that will increase stronger vibrations more than weaker ones, but it sems like it might. Yes, there is more voltage when the relative permeability of the core increases from unity (more changing flux, more voltage: law of magnetic induction), although if you continue to increase the permeability, the increase slows down and stops. But you seem to be saying you think that when the permeability goes up the ratio of different harmonics might change. I do not think that this possible. Maybe I am misunderstanding what you mean? |
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Post by gckelloch on Jan 22, 2022 16:07:48 GMT -5
Check out his blog on pickup function. He specifically models the string flux line paths of an A5 vs higher permeability pole. There will simply be more V If more of the lines from the string pass through more of the coil. How is that controversial? I can't say if that will increase stronger vibrations more than weaker ones, but it seems like it might. Yes, there is more voltage when the relative permeability of the core increases from unity (more changing flux, more voltage: law of magnetic induction), although if you continue to increase the permeability, the increase slows down and stops. But you seem to be saying you think that when the permeability goes up the ratio of different harmonics might change. I do not think that this possible. Maybe I am misunderstanding what you mean? What if one of the stronger inner flux lines passes through the top of the coil only with the higher permeable pole? Might not the stronger string vibrations be more emphasized if the weaker ones don't cause that stronger flux line to pass through the top of the coil? Just speculating on that, but it seems possible. It just so happens Scott recently added a blog entry on pickup Q. The effects of permeability are covered in a previous entry: lawingmusicalproducts.com/dr-lawings-blog |
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Post by antigua on Jan 22, 2022 23:53:23 GMT -5
I am confused. If there is a significant difference in Q, you hear it. But why should there be very much difference in Q between A5 and A3? It is the conductivity of the material that matters for the Q, and I suspect that it is not all that different. They're slightly different, I've tested this in the past guitarnuts2.proboards.com/thread/9039/alnico-pole-piece-comparison and it shows A2 / A3 having a lower Q factor than A5. I'd guess that there is a slight difference in conductivity between A2 and A3 versus A5. I've also seen this pretty consistently when testing Strat pickups with A2 / A3 versus A5. Some people seem to believe A4 should behave like A5, but my sample was very similar to A2 and A3, and I've never IIRC seen an Strat pickup with A4 pole pieces, so I'd concede that my A4 pole pieces might not be proper examples of AlNiCo 4. |
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Post by antigua on Jan 23, 2022 0:06:14 GMT -5
It's not the freq response, but the relative difference of the stronger vs weaker string vibrations for each note that is accentuated by coil proximity. I'm speculating that roughly the same thing happens when the flux lines are pulled deeper into the coil, but it might just increase overall output for a given Gauss level. Scott Lawing might know a definitive answer. I think you have to understand the nature of permeability to figure this out. The steel has magnetic domains that will move in accordance with the magnetic field that they are immersed in, but that immersion of magnetism is not merely from the guitar strings, but all of the magnetism of all the neighboring magnetic domains throughout the steel pole piece. So the guitar string magnetizes the top of the pole piece, and then the magnetic domains at the top of the pole piece that have reacted to the guitar string influence the magnetic domains further down in the steel pole piece to take on their own magnetic polarity. Therefore the magnetism transmits from the top of the pole piece, downwards. They call this the reluctance path, analogous to a conductivity path, because the magnetic field "flows" along the steel "permeable" path similar to how electrical current flows along a low resistance path. But because all magnetic fields extend outwards to infinity, all of these interactions have to be thought of as gradients, not hard cut-offs with hard boundaries. |
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Post by antigua on Jan 23, 2022 0:27:51 GMT -5
It's good to see, but also unnecessary to some extent. If you wind PAF replicas, for example, and the only thing that varies from one to the next is the amount of wire and the magnet type (and that's the business model for dozens of sole proprietors making and selling pickups) , the bode plot will look nearly identical for all of them, because so much of the plot line owes to the eddy currents, and if you're using a PAF platform for all your pickups, then the eddy currents are about the same in all cases. The same goes with making Fender style pickups. I think it's a necessary step towards the buying public better understanding all pickups. If you're saying that most PAF replicas are sonically similar, then that's not something that your average pickup-buying Joe knows. So if seeing similar bode plots at least raises that possibility in their mind - if standardized plots became more commonly published - and buyers thus approached buying a supposedly "better" PAF with a bigger grain of scepticism, then that's a good thing I think. But the pickup companies might lose sales by fewer unnecessary purchases that way, if some of the smoke and mirrors they use to distinguish between their products and their competitors' was replaced by something more objective. So bode plots are probably not something that most are going to publish voluntarily (assuming some?/most? measure them internally). Buyers will need to demand bode plots from them. Incidentally the axesrus guy did a FB post on PAFs recently, making a distinction between the vintage-correct parts and the much smaller number of things that actually makes them sound vintage. He seems to approach the whole industry with a good dose of scepticism. It seems like more pickup enthusiasts are catching on, and some new entrants into the pickup making game seem to be more receptive to taking a technical view of pickups, where as makers who are more established and have been operating more wholly on subjectivity, are mostly adamant about remaining subjective, and in some cases seem to have become even less technically objective than they had been prior. One pickup maker who is no longer in the business tried to tell me that he took down technical specs because they confused his customers too much, causing them to ask too many questions which cost him his time. So far none of the new pickup makers who I've seen embracing objective specs has seemed to establish a noteworthy market share, but hopefully that will change in the coming decade. I think as cheap pickups from China become more popular, domestic winders will have better luck drawing a more objective distinction between their product and whatever can be had on Amazon for dirt cheap. |
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Post by gckelloch on Jan 23, 2022 1:47:06 GMT -5
It's not the freq response, but the relative difference of the stronger vs weaker string vibrations for each note that is accentuated by coil proximity. I'm speculating that roughly the same thing happens when the flux lines are pulled deeper into the coil, but it might just increase overall output for a given Gauss level. Scott Lawing might know a definitive answer. I think you have to understand the nature of permeability to figure this out. The steel has magnetic domains that will move in accordance with the magnetic field that they are immersed in, but that immersion of magnetism is not merely from the guitar strings, but all of the magnetism of all the neighboring magnetic domains throughout the steel pole piece. So the guitar string magnetizes the top of the pole piece, and then the magnetic domains at the top of the pole piece that have reacted to the guitar string influence the magnetic domains further down in the steel pole piece to take on their own magnetic polarity. Therefore the magnetism transmits from the top of the pole piece, downwards. They call this the reluctance path, analogous to a conductivity path, because the magnetic field "flows" along the steel "permeable" path similar to how electrical current flows along a low resistance path. But because all magnetic fields extend outwards to infinity, all of these interactions have to be thought of as gradients, not hard cut-offs with hard boundaries. Regarding the effect of the magnetized string on the pole piece: I don't think there is a significant effect compared to the permanent magnetism within the pole piece. The dipole is emanating from within the pole (or below it if that's where the magnet is). The mass of and gauss of the relevant magnetized portion of the string is also many x's lower than that of most pickup pole pieces (or the magnet below them), so how much variance in pole piece flux could there be compared to the fluctuation from the vibrating string? Scott showed an example of how it doesn't make an audible difference if the magnet is located below or above the string using a pickup that had only unmagnetized pole pieces. I think the old V being derived from the magnetized string causing the entire field to oscillate belief has been sufficiently debunked by him, and others b4 him. If that's what you are referring to, I suggest abandoning it. In short, it sounds like you are proposing a sort of perpetual motion machine. If the string flux were to increase the flux in the pole, then the increased pole flux would then increase the string flux, and so on. Surprisingly, I think Scott makes too much of the Q-factor, when lower to upper note harmonic balance can be at least as effective to achieve the desired warmth or clarity per string and pickup position. Turn the tone knob down a notch or two with a higher Q pickup, and you'll achieve the same result as a lower Q pickup, assuming the same Gauss. Controlling note timber with polepiece height and wire gauge makes more sense. Use the thinnest wire gauge you can to get the most wraps within the tightest space closest to the top of the pickup, and adjust pole piece and coil height for note timber. He could do that specifically for each string with his designs. |
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Post by antigua on Jan 23, 2022 3:30:53 GMT -5
Regarding the effect of the magnetized string on the pole piece: I don't think there is a significant effect compared to the permanent magnetism within the pole piece. The dipole is emanating from within the pole (or below it if that's where the magnet is). The mass of and gauss of the relevant magnetized portion of the string is also many x's lower than that of most pickup pole pieces (or the magnet below them), so how much variance in pole piece flux could there be compared to the fluctuation from the vibrating string? Scott showed an example of how it doesn't make an audible difference if the magnet is located below or above the string using a pickup that had only unmagnetized pole pieces. I think the old V being derived from the magnetized string causing the entire field to oscillate belief has been sufficiently debunked by him, and others b4 him. If that's what you are referring to, I suggest abandoning it. In short, it sounds like you are proposing a sort of perpetual motion machine. If the string flux were to increase the flux in the pole, then the increased pole flux would then increase the string flux, and so on. The voltage comes from flux *change*. The static flux, which is to say the permanent magnet, generates zero voltage, because it is unchanging. I've done a test, I can find the link if you want, measuring the output voltage of steel versus AlNiCo pole pieces, and the steel pole pieces have a higher output, somewhere around 2dBV higher. So the changing magnetic field of the guitar string generates a voltage per Faraday's law, the steel pole piece reacts to that changing magnetism, and it's own magnetism also changes, resulting in a greater overall change, generating yet more voltage. But it's not perpetual motion, it's a redirection of more energy away from the guitar string than you'd others have, because technically, the more magnetism the pickup receives, the more the strings are damped, it's actually loading on the guitar string, due to Lenz's law. The energy that a guitar pickup puts out is not free energy, the higher the pickup output, the less the guitar string moves, but this loss is small that's imperceptible. If guitar pickups were so efficient that they could somehow capture a larger portion of the moving string's energy, only then would the loss of kinetic energy in the moving guitar string be noticeable. The steel pole pieces increases the efficiency with which the pickup takes energy from the guitar string and transfers it to the guitar amplifier. It's the same idea as how steel laminations in a transformer, further enables the transfer of power across the transformer. Guitar pickups without steel pole pieces are, in some sense, a flawed design for the fact that they don't do more the enable the transfer of energy from string to coil. When Leo Fender put the big metal shield around the Jaguar pickups, it functioned as shield, but it was also so thick that we could assume the intention was to reduce the magnetic reluctance in his pickups, but gave up on the idea when it didn't prove to make enough of a difference in terms of shielding or output. Not to keep drifting too far off topic, but a lot of people also seem to think that magnetic pull "dampens" the strings, but that's not mostly what happens either. It's true that a tiny bit of heat is generated and energy escapes the system that way, but mostly what happens is the magnet is ever so slightly bending the string, not only making it stiffer, but asymmetrically stiffer, shifting kinetic energy away from fundamental string movement into harmonic movement, and that's what underlies the characteristic difference between, not only stronger and weaker magnets, but pickup height with respect to the strings. Surprisingly, I think Scott makes too much of the Q-factor, when lower to upper note harmonic balance can be at least as effective to achieve the desired warmth or clarity per string and pickup position. Turn the tone knob down a notch or two with a higher Q pickup, and you'll achieve the same result as a lower Q pickup, assuming the same Gauss. Controlling note timber with polepiece height and wire gauge makes more sense. Use the thinnest wire gauge you can to get the most wraps within the tightest space closest to the top of the pickup, and adjust pole piece and coil height for note timber. He could do that specifically for each string with his designs. He's been talking about Q factor for as long as I can remember, and yeah, guitars have tone and vol pot values chosen specifically to destroy the Q factor. To be honest, I've probably made too much of the Q factor at times, when talking about the difference between A2 and A5 for example, but Q factor remains important when talking about abnormally low Q factors due to eddy current losses. The big debate about brass and nickel silver involves Q factor, and it is rather important in that context. |
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