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Post by antigua on Feb 20, 2024 1:54:12 GMT -5
Hi Antigua. I have a question about the approach on the flux measurement. I have recently bought a gaussmeter so that i can use that data on my pickup evaluations & my reviews. How do you get only one value like "screw250G/slug 280G" because i read more non uniform values. For example last night i measured those data from my 8,5K Pearly Gates; Slug=from low-E to hi-e 234 - 268 - 270 - 248 - 253 - 227 Screw=from low-E to hi-e 272 - 248 - 250 - 279 - 265 - 265 So do you calculate the arithmetic mean like 250G for slug and 263 for the screw coil? Or measuring on spesific point like "data of the pole piece top of G string only"? Thank you so very much Nothing fancy, I just measure the center of the D and G poles and come up with an average, to the nearest 25G. The edges of the pole pieces often show a higher Gauss value, but I stick with the centers. Based on what you measured I would round it off to 250G. The flux density with a PAF / P-90 sized bar manet is a lot less consistent that people realize. Not only do you get a random assortment of values from the pole tops, but if you remove the magnet, and run the probe along the long edges of the magnet, you will find that the Gauss varies along the magnet itself, sometimes even more than the pole and screw tops do. The screws and poles actually serve to even out inconsistency in the magnet itself, by combining the flux density of weaker and strong parts of the AlNiCo bar into the steel, which has a higher permeability, and better metallurgic consistency than AlNiCo.
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Post by antigua on Feb 20, 2024 1:50:46 GMT -5
I've never had Lace pickups before and I'm wondering if they could be the solution I'm looking for in a neck humbucker that can split to a low-noise Strat-ish single coil tone. I'm having trouble understanding how the Dually's relate to the rest of the Sensor lineup. Lace and others suggest that the Dually's are simply two of the regular single coil models mounted adjacent to each other, but is that true and can they be swapped with the regular single-coil models? antigua are you familiar with the mounting of the coils to the Dually chassis, and are the individual coils really the same geometry and performance? I've never looked at Duallies. The Lace frame is proprietary, and they use epoxy, so you can't even take them apart. I don't think you could swap one for a vintage style coil. The main reason I don't like the idea of the Duallies is that the only think that sets Lace Sensors apart is their inductance values. You would have two single coils side by side for no other reason than to achieve two different inductances, basically two different EQ profiles. Some people might be happy with that, but I'd rather just have one pickup or another, and get the different EQ profiles with an EQ pedal, or even just adjust the tone knob. It's even possible to just add a capacitor in parallel with a switch to drop the resonant peak by some amount.
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Post by antigua on Feb 20, 2024 1:45:01 GMT -5
The Bill Lawrence Q Filter is a non destructive mod. In theory you could wire it up outside of the guitar, between the input jack and the guitar cable, with a little box. The inductance values are so high that I'd consider the dark tone question and open and shut case, regardless of the 1 meg pot or anything else.
When you measure value with the DE-5000, you only need:
Ls at 100Hz (the lowest freq) Cp at 100kHz (the highest freq) Q at 1kHz (a value that is both high, and still below resonance, to measure eddy currents) DCR (plain old DC resistance)
The other values are not needed, either because they're not very useful or they're not applicable.
The resistance at frequency measurements, Rp and Rs, might actually have some use in eddy current determination, but I havent looked into it yet. The thing about a PAF clone is that because they all use mostly the same parts and geometry, the eddy current aspects are usually known, from having observed them in so many other PAF clones. It's mostly useful when you have reason to believe a given pickup will have more or less eddy currents that you would expect, like if the pickup maker claims they're using nickel silver, but you suspect they've used brass, or something like that.
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Post by antigua on Feb 18, 2024 21:53:22 GMT -5
Thanks for the details. The inductance values are very high for the bridge pickup, and rather high for the neck. 9 henries is hotter than a JB. I'm not surprised Robben Ford chucked all of it out.
The only way to add sparkle back once you have pickups with high inductance, aside from split or parallel, would be to install a Bill Lawrence Q Filter, which is an inductor with a cap and resistor added in, which effectively lowers the inductance of the pickups. If you can't dedicate an tone control to a Q Filter, you can wire it as a push pull, so that it's other in circuit or out of circuit.
The single button split with B+N single coil humbucking is similar to how they set up the new Meteora model with the Fireball humbuckers.
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Post by antigua on Feb 14, 2024 21:31:37 GMT -5
I really like "according to Zollner...". I think of prompting with this as a way to get it to go looking in Zollner's book. Not sure if it will delve into translated PDF files. The translations are excellent, but it still might find some way to get confused. I need to think of the right "hook" to introduce this. Hi guys, I read this today and thought I would give this a try, I went on Bing's AI and asked it to look into "Physics of the Electric Guitar" by Zollner and gave it the link to the english translation. It was a question relating to the design of bridges not pickups, but none the less it's said it could not look into the book due to copyright. I did send a note to Dr. Tilmann Zwicker on this for his information. Should it be turned loose to AI? Thanks for trying that and contacting Tilmann Zwicker. I'm sure he'd like for it to be ingested for AI, he translated it in order for the work to reach a wider audience.
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Post by antigua on Feb 13, 2024 17:28:12 GMT -5
Thanks antigua, this is very interesting since we expect the single coils to be getting some induction boost from each other when used singly already, and whatever this boost is is increased further when they're operating in parallel. When in single-coil mode would the inductance be affected at all based on whether the unused coil was open or closed? I saw your write-up here about the damping (and, based on PRS's design changes soon after you wrote that, seems they may have too!): guitarnuts2.proboards.com/thread/7769/damping-caused-unused-splitting-humbuckerMy understanding isn't strong enough to know if there is any relationship here between the damping effects and any changes in induction. I don't really know. The graphs show a higher frequency when the second coils is closed, and that suggests a lower inductance, but that seems counterintuitive. I can do a test later and find out. If you don't already own a DE-5000 I'd recommend picking on up because you seem to have a want for good volume of inductance information, and the DE-5000 makes its fairly effortless.
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Post by antigua on Feb 13, 2024 11:43:34 GMT -5
Thanks! I was on the assumption that two typical humbucker coils in series is about 15% more inductance than the sum, but you're saying that 11% is probably a more typical number? antigua following up with some additional thoughts here: The 11% additional inductance from the coupling, does that apply to parallel wiring as well? I.e. for coils with an inductance of 2H we'd get: ((2*2)/(2+2)) * 1.11 = 1.11H? Also, does this account for the difference in split tones when leaving the other coil out of circuit versus shunting to ground? Other coil out of circuit, remaining coil: 2H Shunted coil to ground, remaining coil: 2*1.11 = 2.22H? Yeah the parallel inductance is greater than (coilA * coilB ) / ( coilA + coilB ) I checked with a couple humbucker that I measured parallel inductance for, a most of the time I don't measure that. Both come out higher than what the math suggests. For the SD 59, the parallel inductance is 13% greater than what the formula suggests for the coils by themselves. guitarnuts2.proboards.com/thread/7763/seymour-duncan-custom-analysis-reviewguitarnuts2.proboards.com/thread/7995/seymour-duncan-duckbucker-analysis-reviewWhen I say coils by themselves, they were in-situ when I measured their inductance, but if I had unscrewed them from the base plate and have them physically far apart, their inductance would drop by some small amount, I'm not sure by how much.
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Post by antigua on Feb 12, 2024 11:43:11 GMT -5
Cool! Feels good to be learning stuff Now I feel like I better understand the focus that PRS has taken around increasing inductance with moderate resistance. That helps get that higher-output higher-clarity humbucking tone they're aiming for while simultaneously creating an inherently better-splitting pickup. Would it be reasonable to say that this approach also helps mitigate the (split-coil) difference between steel poles and magnetic poles? One thing that's important to remember about the higher Q factor is that it's not a desirable sound, usually. You can see here that a no load pot gives the highest Q factor. Guitar makers use 250k or 500k pots intentionally to reduce the Q factor. The two in parallel brings that actual resistance down to 125k or 250k respectively. I don't know what PRS has been saying about inductance and resistance, but to date they've been making a lot of dubious claims about physics and guitar, and that sounds to me like another one. Magnetic pole pieces give you a higher Q factor, because the AlNiCo magnet has higher electrical resistance than steel, so you get less eddy currents, less reduction in both high frequency and less reduction in Q factor. Fender uses 250k pots with their single coils to reduce the shrill sound of the high Q factor. It's true that when you split a humbucker, one reason is sounds anemic is because it has a lower Q factor than what you'd hear with magnetic pole pieces, but also the strength of the magnetic field is only about 25% as strong at the pole tops of the split humbucker. This is because a direct AlNiCo magnet is stronger than an AlNiCo magnet mounted to the underside of a humbucker, having it's magnetism redirected by steel pole pieces. Even a Strat pickup with a ceramic magnet and steel pole pieces (as found on cheap import guitars) is about half the magnetic strength of a vintage AlNiCo 5 Strat pickup. The stronger magnetism also results in more treble response at the pickup, which is why Strats and Telecasters sound so bright, even with 250k tone and volume pots. You can get a pickup with steel pole pieces to have the higher Q factor by simply using 1meg or no load pots, but a lot of people who try this will tell you it sounds bad. The steel pole pieces also drive up the inductance of the pickup a lot, due to high permeability, so they almost always have a lower resonant peak at the same time. For example, a Strat pickup with AlNiCo pole pieces will be 2 henries, with steel pole pieces that same pickup will come out to 3 henries. And if a high Q factor is bad, a high Q factor at a lower audible frequency is even worse. If a person wanted to really fake an AlNiCo pickup with steel, they would have to assure that the inductance is especially low, put a very strong magnet underneath, and use high resistance tone and volume pots... it's easier to just use a real AlNiCo poled pickup than go through that kind of trouble. All together it's a balancing act, but the main point is that there is no reason to strive for a high Q factor if you're going to turn around and reduce it with 500k tone and volume pots.
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Post by antigua on Feb 12, 2024 11:22:56 GMT -5
I'm still impressed that it can BS as well as it does. Is it really worse than the BS pickup makers put out?
A lot of the mistakes become apparent only after you connect the dots, like the distinction between whether voltage causes current or current causes voltage. A lot of times Chat GPT has the ability to come up with the right answer after you inform it of it's mistake. There has also been talk about Chat GPT being "lazy", and this does seem like laziness. I don't understand how the algorithms work, but I wonder if the mistakes are due to a lack of self-checking. Like when it makes up facts, why can't one Chat GPT take the answer of another Chat GPT, and interrogate it's answer before it presents to the end user?
Hopefully at some point it will see Manfred Zollner's work, and we can prompt "according to Zollner..."
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Post by antigua on Feb 11, 2024 16:47:49 GMT -5
I think it's time for me to learn more about this stuff. I finally went over one of your analysis, of the Epiphone 57CH pickup, and it's all extremely interesting. I've never looked into pickups this much, even after all the stuff youve posted at ST since I've been there. But I think it's time to start learning. Now that I've started buying better pickups, I've become a lot more interested in all of it. I know you've tested Seth Lovers and 59s so I'll have to find your analyses and see what I can learn! Edit: apparently your analyses are quite popular. If you type "Antigua pickup" into Google, it finishes it with "...analysis". That's saying a lot! Nice job! That's funny. I often use Google to look up my old info. That's one of the reasons I post it on the internet. This article about how pickups work is pretty good www.buildyourguitar.com/resources/lemme/ , also Manfred Zollner's work is great gitec-forum-eng.de/wp-content/uploads/2020/09/poteg-5-magnetic-pickups-a.pdf At some point AI will ingest Manfred Zollner's work and AI will understand how pickups work better than any human.
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Post by antigua on Feb 11, 2024 16:34:38 GMT -5
antigua this is great! And the Meteora does look interesting. Do you have an opinion on the 22 vs 24 fret neck pickup positioning? I figured 24 positioning is a bit more like an SG. I see the Meteora also leaves a gap at the neck, but not as much as an SG. Going for the "full hot" approach to Strat and Tele inductance levels I think that means for sourcing coils I'd be looking for humbuckers with inductances of 6, 4.8, and 7.6. As to the reverse wind, isn't it possible to simply flip one pickup's magnet and change which leads are treated as ground versus hot? Yeah you can reverse the magnet and the hot and ground of the humbucker to get RW/RP with both outer or inner coils. Based on the numbers, the total inductance of either coil alone is about 45% of both coils in series. So if you want two 2.7 henry coils, you'd have to part out a humbucker that's about 6 henries.
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Post by antigua on Feb 11, 2024 3:26:49 GMT -5
None of their competitors offer those numbers, and no consumers would know what it means except for like 10 people on this forum. Bass Mid Treble approximations are better than what anyone else offers, and it doesn't give their competitors an edge. So many pickup makers don't have any clue what a resonant peak is, they just think that Formvar gives you are airier tone or whatever nonsense. If you start distilling the characteristics of your pickups to measurable values, you can't charge as much either. Keeping things hand-wavy keeps the prices higher. I think the best companies have faith in their customers. I think if Seymour Duncan presumed their customers were smart, a market of smart customers would open up, and they would dominate that market for as long as their competitors played it business as usual. Instead, they underestimate guitarists out of fear and a lack of faith. I think it's still possible to sell a wide offering of pickups, even if their differentiation is more technical and less Lord of the Rings monsters. There's also lots of aesthetic and color options to set them all apart. Speaker companies, especially Jensen and Celestion, provide lots of technical specs for their speakers, many specs with have parallels to these tech specs of pickups that we talk about, such as their electrical resonance and impedance. With rock and roll no longer being the youth cultural keystone that it once was, guitar is being looked at more as an instrument, and less like Thor's magic hammer for pounding out power chords. I think the anti-intellectual perception of guitar and pickups is on the way out.
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Post by antigua on Feb 11, 2024 3:11:42 GMT -5
Fender did something similar with their Fireball humbuckers for the Meteora model, which has coil splitting guitarnuts2.proboards.com/thread/9926/fender-meteora-fireball-humbuckers-analysis , they made the coils imbalanced for better split tones with still decent series tones. Bridge - Measured L: 4.502H (bridge side: 2.077H, neck side: 1.939H) Neck - Measured L: 4.058H (bridge side: 1.683H, neck side: 1.860H) The neck and bridge are wired reverse of one another, so the neck splits neck side, bridge splits bridge side, and center position split is humbucking. I think it sounds really good. If you go with higher inductance values, another thing worth trying IMO might be a ceramic or AlNiCo 8 magnet in the humbucker to give that sharper sound associated with Fender single coils. Since these pickups will have steel pole pieces no matter what, I'd stick with 500k pots and not bother faking the 250k pots. Personally I like HH a lot better than HSS, even though I have some HSS Strats too. The humbucker bridge is always louder and softer, that's right I said softer, than the middle and neck single coils. It almost makes for a guitar that will do one or the other, but you can't switch between humbucker bridge and single coil neck without feeling some sense of let down, in either direction. With an HH, or an HH that splits both pickups at once, the neck and bridge tones are always more friendly with one another, and the HH guitar can have two distinct personalities depending on whether the two humbuckers are series or split.
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Post by antigua on Feb 3, 2024 0:22:05 GMT -5
I know this is a few years old now, but I had some thoughts and questions around this. The results from this study found differences that were measurable, but below the accepted threshold of human hearing. However, when playing a guitar through a tube amp aren't many of the more subtle differences magnified by applying gain, especially as the signal chain response varies widely across frequency ranges? So that even if some changes are inaudible listened to as a neutral signal, a typical guitar rig would make these differences audible? As a tangent, I thought it would be interesting to post a pic of some of PRS's most recent pickups. I may be wrong, but to me this baseplate actually looks plastic! Is that likely or possible? Thanks for actually executing these systematic studies and publishing them when nobody else seems to be doing so! If we're talking about microphonics, then there would be new content added to the signal, acoustic sound, and maybe that acoustic sound adds in a treble that is brought out by clipping of a tube amp. But if you think about how to isolate a single voice on a recording of a crowded room, you get the best results by using an equalizer to raise up the frequencies of the voice you want to hear. I can't imagine that distorting a signal would make any one voice easier to hear, I think it would just make all of the voices harder to hear, and I think that's true in this case. But when talking about eddy currents, this is not like microphonics, there is no new content added to the signal. The eddy currents function as an unwanted electrical filtering. You could do the same thing with a graphic EQ. This raises the question, if a graphic EQ can bring out parts of a signal, and eddy currents are like an EQ, then can they bring out part of a signal? Probably not, because the eddy currents to not emphasize any part of the signal, rather eddy currents bring all the treble down, called a "high end roll off". Eddy currents roll off treble in two ways, 1) by putting inductive resistance across the pickup's coils, and 2) by cancelling out the high frequency magnetic content of the moving guitar string itself (and that's important because it means a bass plates and a covers and pole pieces will all cause these effects to happen in different proportions). If eddy currents were able to push a particular frequency up, then there would be potential for them to help bring out sounds you might not hear otherwise. It so happens that there is a feature of vintage style guitar pickups that does bring out a particular frequency though, the resonant peak of the pickup. Guitar pickups have a resonant peak somewhere between 2kHz and 5 or 6kHz, and the reason a lot of pickup on the market sound different is for no other reason than they have difference inductance values, and therefore different resonant peaks. If a guitar pickup pushes up content around 2.5kHz, it will sound different than if the pickup pushed up content at 4kHz. Eddy currents only serve to lower the Q factor at resonance, so if anything, eddy currents rob a pickup of whatever special voice that is associated with it, and makes it sound more flat and bland. It's because of the resonant peak that electric guitars sound like electric guitars. Without the resonant peak, they would sound a lot more like an amplified acoustic guitar.
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Post by antigua on Feb 1, 2024 16:36:17 GMT -5
Hi antigua Regarding the baseplate in Tele Bridge pickups, I understand that most use a copper plated steel. I tried measuring the magnetic strength of a Tele Bridge pickup at the top polepiece with and without the baseplate. Based on the readings, the Steel baseplate actually lowers/weakens the magnet strength at the top. I think this will make the pickup output level weaker, correct? I'm wondering why not use a Nickel Silver or Brass (non-magnetic) baseplates like in a P-90 or Humbucker? I tried measuring a P-90 with and without a Nickel Silver baseplate and I can confirm that it slightly increase the magnetic strength at the top. Let me know your thoughts if I miss something or what. Thank you I'm surprised the base plate makes the magnetic field weaker, but I probably realized that when I was testing a few years ago, but I had since forgotten about it. The base plate increases the inductance, some associate the lower resonant peak with power, because hotter wound pickups have a both more power and a lower resonant peak, but there's no merit to the idea that a baseplate adds power. A magnetic base plate might have acted as a magnetic keeper, to stabilize the AlNiCo pole pieces and help prevent them from losing magnetization. It was probably considered good practice prior to AlNiCo 5 being available, but AlNiCo 5 is a stable grade of AlNiCo and doesn't require a keeper in a guitar pickup. PAF humbuckers also have what seems to be a keeper bar, which the screws feed through. Some Chinese pickup makers also figured out that they're not needed and many cheap PAF style humbuckers don't have them either. I think in the case of a Tele or Strat, cavity shielding makes a lot more sense than any shielding attached to the pickup itself.
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Post by antigua on Jan 30, 2024 17:40:20 GMT -5
One shift that happens, when assessing a real pickup with eddy effects and damping with bode plots, is a result of integrating. The integration definitely is the best way to present results because it evens out the curve, and where there are no particular effects happening, gives a flat response. But the act of integrating effectively rotates the curve by 6dB per octave. So if the response is a real one with a rounded peak, it's rotating the top of the hill! So the place that was just before the peak pre-integration, is now at the peak, and its a slightly lower frequency. If there was a perfectly undamped peak of very high Q, as predicted for LC resonance by the simple equation, the peak is so sharp that this shift doesn't occur. This is what I was thinking but couldn't put into words. I can set up the integrator later and do two plots, one off and one on, and see how the peaks vary.
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Post by antigua on Jan 29, 2024 22:51:49 GMT -5
Please tell me, do you believe the measurement of f res can be reliable carried in situ? You're using a guitar cable right? I would instead unscrew the jack plate of the guitar, pull it out, and connect alligator clips to the female end guitar jack, so that there is no guitar cable involved. That should produce a much better result.
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Post by antigua on Jan 29, 2024 22:44:57 GMT -5
This is why I started to go down a rabbit hole of pickups research. No specs, useless user opinions, myths, fairytales... Now I have come to the point my measuring do not give me any reliable results or at least comparable with other people measurements, what scares me I came to this forum, hoping for some help. I have hypothesis that my probe still having ferrite core which permability is lower than air is an issue, but why it distorts readings of only a few humbucking pickups to such extent? BTW I tried different probe inductors. Ken suggested fluorescent lights ballast. One of them apeared to be 10nF cap and the second one a coil made of aluminium stripe did not propagate anything to be analyzed. 500mH wah-wah inductors did not work either. I was just lucky to find a small transformer that does a job. I hope there must ba a way to reliably measure pickups in situ and I believe such approach while not offering a great accuracy, is better because one can test the whole RLC network not only a pickup and it is what user is hearing. BTW2 listening to white noise modulated by guitar filter is very nice experience. The DE-5000 can be had for about $100 to $130, depending on where the best deal is. I think it's a good investment. It can also measure capacitance at 100kHz in Cp mode, and that's good for testing cables and other components as well as pickup, and it even has a DCR settings. It's really a one stop shop meter for our needs. I've acquired some pricier LCR meters that do one thing better, but none of them are as well rounded. And then there's the WT10A magnetometer for only $80 on Amazon. The price on that has come down, it used to be over $100. Most electronics from China have increased in price lately, so that's a nice surprise. With those two meters alone you can know most all you want to know about any given pickup. The main thing you lose out on if you forego bode plots is studying eddy currents by seeing how the impedance curve changes, lets say; with or without a metal cover on the pickup, or determine what sort of metal the cover is made of based on the Q factor of the bode plot. That's more about experimentation than gathering data for existing production pickups, because usually the type of metal, and the eddy current profile for a given pickup on the market will be known or easy to guess. The DE-5000 also has a Q measurement, so technically it has the capacity to illuminate about eddy current losses, but that's an ongoing project, trying to figure out what test frequencies and test scenarios result in usable information. Sadly the Velleman USB oscilloscope I like to use is no longer manufactured, and not good replacement exists on the market, except maybe the Digilent Discovery 2. A computer audio interface is probably the best bet now, but I haven't had a need to go that route since my Velleman is still functional. For a probe inductor, you can just buy some fine magnet wire and wrap it around a popsicle stick, here's a pic of mine guitarnuts2.proboards.com/thread/7890/coil-productivity-respect-permeability-proximity , I used some leftover 42AWG wire. You can take off of some cheap guitar pickup. About a hundred wraps will give you a good exciter, but you can wrap it two or three hundred times and have a really good test probe. The self-resonance of the test probe needs to just be much higher than that of the guitar pickup itself. With a DE-5000 you could quickly see what the inductance happens to be of any test probe you create, maybe a hundred henries, but no matter what, it's going to be a small fraction of what you see with the guitar pickup under test. If you are interested in seeing the sound as you hear it, then in situ is good, but you just have to keep in mind that it's a more complicated network than a simple three part RLC model, because you have the capacitance of the cable, and the capacitance of the pickup's own connection cable, and the load resistance of the pots in between those two sources of capacitance. As mentioned above by Yogi B, the math is more complex.
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Post by antigua on Jan 29, 2024 13:45:08 GMT -5
I am lost. If 200mH difference is oversold, 200Hz of f res is too, instead gauss at the strings is relevant which can be adjusted by changing height of a pickup as easy as swapping 300pF cable to 600pF... Yet you publish results suggesting 10Hz accuracy knowing you can not measure with such accuracy. And yes, poeople trying to demonstrate difference between pickups probably use the same pickup height, cable and amp settings. If they were matching f res with capacitances to 50Hz and amp gain to pickup output to 0.5dB, it could end in conclusion there is no difference at all. Back to my Pearly Gates Bridge as Ken Willmot amateur method testing in home studio enviroment. I adapted it to my needs. While I like RMAA I want to keep it simple and real time, this is why I use white noise and RTA, knowing that my accuracy is about 100Hz. Here is RTA reading of PGBL sitting in a strat pickuard eguipped with 500k pots, connected with 300pF cable to HiZ input of my audio interface. I use 300pF cable because the results are close to yours in case of Fender 57/62 and VN pickups. Here are superimposed readings of uncorrected reading and 6dB/oct LP filter. As you may see I cannot determine f res implementing "integrator" this way: You may say that my capacitance load is wrong, but Ken proposes a method for estimatiting pickup inductance by rising load above cable capacitance matters using 100nF cap. I happen to have 47nF tone cap in my circut so after setting the tone pot to 0ohm value, here what I get: Now calculating inductance out of f res 340Hz and 47.5nF load I get 4.6H... and my measured f res is still 500-700Hz above Antigua Pearly Gates Neck reading 4.151H... So what is the conclusion? My Pearly Gates Bridge is not Antiqua Pearly Gates Bridge? Or Ken/My measuring method is wrong? Or something else? I put the values as shown on my LCR meter or the Velleman output. I'm not saying 200mH is irrelevant in terms of pickup testing, more that it's irrelevant when it comes to making a purchase decision about guitar pickups. If you have two pickups and they have an inductance that's within 200mH, then it's effectively the same pickup, because the difference in frequency will fall within a window of variance that you get from varied cable capacitance. If the difference is inductance is more significant, then it will surpass the difference expected from different lengths of guitar cable. For example, 3H and 500pF comes out to 4.1kHz, but change that to 1000pF, the frequency drops to 2.9kHz. But if you start with 3H and 500pF, jump to 3.2H, the frequency only drops from 4.1kHz to 4.0kHz. The precision or lack of is just an artifact of the measuring tools. Even though people test pickups with a given rig, it's never the less the case that it's easier to modify the rig than it is the pickup. At the end of the day I do pickup testing for practical reasons, so I think a lot about whether a difference is audible or not. Almost every pickup I've tested I ended up using in a guitar for some period of time. I've only ever bought two or three solely to measure their values. All of this is a necessity thing for me, the pickup makers don't provide this information so I couldn't make informed buying decisions. I've mostly come to the conclusion that the market is saturated with near identical pickups with trivial electrical variation, and that much of the time the right move was probably not to buy new pickups at all. I personally haven't derived inductances from swamping the pickup with a known capacitance, I almost always use the DE-5000 or the Extech 380193, set to 100Hz or 120Hz, because it's just way faster. I believe you have to unsolder your pickup from your guitar to the unloaded peak frequency, because the guitar cable and the control pots are going to add variables that are harder to account for and lead to confusing errors. I never measure guitar pickups with them still connected to the guitar, too much variability to work around. Add to this that the pot and cap values are nominal, they tend to have a 10% margin for error, so you would have to measure the true values of the pots and caps before solving for them in the peak resonant calculation. Ken knows a lot more about this than I do, both the process of solving for inductance with a known large capacitance, and using an computer's audio interface for testing. I've stuck with USB oscilloscopes and LCR meters myself. Something else I can speak to from testing though is that even though the DC resistance varies easily from one pickup to another, the inductance tends to be very consistent because the pickup manufacturer set their machines to a specific turn count, and the inductance will follow closely with the turn count. If your purpose here is to make sure your Pearly Gates was manufactured correctly, I'd say there's little doubt that it is. I might check the inductance if I though it were a counterfeit, and I wanted to see how close the possible counterfeit's inductance is to the real thing.
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Post by antigua on Jan 28, 2024 16:57:33 GMT -5
It's the same difference that you'd get from lowering the pickups Can we revise that after years? I have calculated f res of various magets in the same pickup from yt video presented in that thread: guitarnuts2.proboards.com/thread/9535/magnet-materials-effect-on-inductanceAt C=600pF A2 4.53H 3.05khz A5 4.37H 3.1kHz A8 4.23H 3.16kHz CER 4.09H 3.21kHz So we can expect audible change at least from changing A2 to ceramic magnet. The second issue I have when I check your measured values using a f res formula. 5.097H, 126pF parasitic and 470pF load capacitances should make 2.89kHz resonant frequency, not 2.64kHz. What am I missing here? Can't I directly sum parasitic and load capacitances? My third problem is I measured f res of my old Pearly Gates Bridge. The same DCR, no cover. I have no inductance meter. All the measuring I have done so far using my magnetic exciter, guitars, about 300pF cable and audio interface HiZ input, complied with your measured Fender 57/62 and Vintage Noiseless pickups. In case of Pearly Gates Bridge f res is 3.5kHz. I can imagine something can be wrong with my approach/expertise but almost 1kHz difference is much too much. All my fellow guitarist making only subjective opinions on pickups consider PG as "humbucker for strat" - much brigter than any "regular PAF". At 2.6kHz it is just regular... I don't think a change in inductance of 200mH should be oversold, because there is a margin for error in the final resonant frequency due to guitar cable and hookup lead capacitance. I suppose if you are already using the lowest capacitance guitar cable possible, and you still want a higher resonant peak, a magnet swap from A2 to A5 would gain a little more treble, but if you're going in the other direction, added capacitance would make more sense than a magnet swap. There is a difference in magnetic strength, and that can't be affected electrically, it's a physical difference. I shouldn't say swapping the magnet has no effect on the resonant peak, but it's not a big difference, it's not a unique difference, and it's not the best way to alter the resonant peak of a pickup, and at the same time it will effect the magnetic strength, which is the primary function of the magnet, which aside from raising or lowing the pickup, is the only way to vary that parameter. A stronger magnetic field results in more treble, because 1) it creates asymmetry in the guitar string, transferring energy away from the fundamental movement and into the harmonic movement, and 2) I just learned recently, if the stronger magnetic field succeeds at saturating the guitar strings, to where they can magnetize no further, the magnetic field of the guitar string become more focused towards the center, also resulting in more treble. I'm not sure how to best explain it, it was explained here music-electronics-forum.com/forum/instrumentation/pickup-makers/pickup-theory/990050-magnets-in-pickups/page2#post991512 There's a magnetic cancellation in the guitar string above the pole piece, but if they steel is magnetized as complete as it can be, that cancellation area will be more narrow, creating a sharper focus that allows higher / narrower harmonics to be picked up by the coils. Regarding the 2.64kHz loaded peak, I got that directly from the bode plot, I don't have a good explanation for why the bode plot doesn't match calculated values. The bode plot from the Velleman is not super precise, it tests in steps, so to some extent it will "step" over the actual resonant peak. It tends to be the case that the bode plot shows lower frequencies. I have seen this happen with multiple test setups using all different components. The oscilloscope or integrator only add about 10pF to 20pF capacitance. I just present the data as it is and that's how it comes out. Maybe the true peak is actually supposed to be a little beyond the plotted peak. There are two models of Pearly Gates, the Pearly Gates and Pearly Gates Plus, which was made for Fender, IIRC Tim Shaw asked Seymour Duncan for the Pearly Gates Plus. I don't think there is anything about it that makes it better suited for a Strat, technically. According to the story, Tim Shaw liked the Pearly Gates, but wanted a slightly hotter version, and the only difference is that the Pearly Gates Plus has an AlNiCo 5 bar. It amounts to nothing more than marketing, IMO. I think people who buy an HSS Strat are looking for a Gibson-like tone from the bridge, so there's no need to do anything beyond placing a generic Gibson-like humbucker in the guitar. Also in that video, he's using a cheap LCR meter that likely has a fixed test frequency of 1kHz. It's better to test with a meter like the DE-5000 which can offer a low test frequency, 100Hz or 120Hz, so that eddy currents won't interfere with the meter's ability to calculate the inductance. Humbuckers in particular have a lot of eddy currents because of the steel pole pieces.
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Post by antigua on Jan 25, 2024 12:45:41 GMT -5
Hi guys, brand new to building and testing pickups. Some great info on here. I watched that video and it’s great to get an insight how the big guys do it. As far as testing goes most of the measurements like RCL is all ok and easy enough to find. I’m honestly still working on how to properly interpret this kind of data for practical purposes and I honestly need to do a lot more testing and reading. He mentioned that the strum test was to test output. On his website he shows a pretty crude scale for output but also a tiny bar graph for Bass Middle Treble, I wondered how exactly the proper figures to produce these would be derived in order to have a purely practical way for comparison. Thanks. The bass/middle/treble values are made up, they have to be because a guitar pickup is one or two coils of wire with no other circuitry ahead of the connection cable. But actually there is other circuitry in the form of unwanted resistance, inductance and capacitance, and it's because of all three that the pickup has a resonant peak frequency and a low Q factor. If it were possible to make a pickup with no R, L and C, there would be technical upsides, like a more broad frequency response and less susceptibility to noise, and that's realized with low impedance pickups and active pickups. Fishman Fluence can claim to have bass mids and treble because they actually do fit their active pickups with a filter circuit, so that they can offer several sound profiles with one pickup. Virtually any passive guitar pickup with a DC resistance over 6k ohms will have a resonant peak that is audible to the ear, and what distinguished almost all the passive pickups on the market is little more than the frequency that high end content is rolled off. More inductance = less treble. Another reason you can't characterize a pickup as having bass middle and treble is because that depends so much on where the pickup is positioned in the guitar. Any pickup in the neck position will have a lot more proportionate bass than any pickup in the bridge position. A guitar pickups functions as a filter, but for marketing purposes, pickup vendors try to portray them as the source of the sound, which is actually the guitar strings. As for strumming, people don't realize how hard it is to strum consistently. It sounds mostly consistent to our ear, but we're often looking for a difference that is much smaller than our ability to strum consistently. Not only do you pick with more or less force, but hit the strings with different angles of attack, and pluck in slightly different places, which all add together to make for a different result, strum for strum. But that's why guitar sounds alive and synthesizer music sounds robotic. It's very hard to play guitar in a way that seems robotic, and that's good for music but a problem for pickup or general guitar testing. That's probably why there is so much magical thinking around guitar, it's very difficult to objectively test guitars without fancy equipment. For practical comparison, I just need to see the inductance of a pickup most of time time, the treble response is inversely proportionate to the inductance. The perception that a pickup has a lot of bass or mids is just an byproduct of lacking some amount of treble. For a given style of pickup, the amount of resistance represented by eddy currents will be inherent to the style of pickup, Fender single coils very low, anything with steel pole pieces will have a higher resistance, and therefore a low Q factor. That's why Fender uses 250k pots, but most other pickups are paired with 500k pots, it's a lot more trivial than inductance. The fact that Seymour Duncan provides BMT, but not inductance, tells me that they want customers to be confused. It makes it easier for them to offer new products that are very similar to existing products, without having to make it so obvious, and it creates the impression that the creative input of their product designers is more substantial than it really it. Almost all the pickup makers want to be seen as artisans, but there's just not that much dynamic and dimension to a coil of wire mounted to some kind of frame.
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Post by antigua on Jan 9, 2024 17:30:37 GMT -5
Here, incidentally, is an example of a guitar equipped with an active EQ circuit intended to simulate a neck pickup. But you cannot do that with a single EQ circuit. The location of a pickup determines the relative intensities of the string harmonics. But the actual frequencies are different for each string (because the harmonics are the same). Therefore each string would have to have its own pickup and equalizer. Technically this is true, we're talking about a difference in harmonic timbre versus amplitude by frequency, but I think if you cut out a portion of the frequency out, you get a result that is sonically similar to the altered timbre, I think because the neck pickup timbre is defined by particular harmonics being greatly reduced, and with the EQ you are taking away amplitude that roughly overlaps with the missing harmonics of the neck pickup. The reason I'm as confident about this as I am is because I made my own Veritone control, and chose my own cap values, and notices some cap values did make the bridge seem a lot closer in sound the the neck or middle pickup, depending on the value of the cap. The bridge pickup has relatively even harmonic amplitudes compared to the neck and the middle, so it can serve as a good base signal to be reduced into other timbres. With active EQ, the RLC filtering would be a lot more robust than what a Veritone control can do.
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Post by antigua on Dec 29, 2023 0:37:25 GMT -5
I considered starting a new thread for this, but I've always found it more useful to have as much information as possible about a given topic in the same thread — it's much more user-friendly for people who arrive here via Google. A company called Blue Cat Audio make a plugin called Re-Guitar: a "pickup simulator" for DI guitar, including emulations of both hollow-body electric guitars and steel-string acoustic guitars. Here's a screenshot, from their website, of the user interface: ... I got this plugin at a steeply discounted price a while ago, but I haven't had much time to play around with it. If anybody wants to hear how it sounds, I can easily run a DI guitar recording through it for you. That's interesting. The difference between single coils and humbuckers, and even acoustic guitar, seems to be accomplished with relatively simple EQ, and it's possible to approximate different pickup positions with more complex comb filtering profiles. it's actually possible to make a bridge pickup sound a lot like a neck pickup with a Varitone style inductor/cap RLC filter, and I'm surprised that's not more common with single pickup guitars. I'm not sure what technique they use, but I'd guess plugins are still mostly keeping it simple, but the new audio AI processing will probably blow the lid off digital processing in the next few years.
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Post by antigua on Dec 29, 2023 0:17:59 GMT -5
So if you're going for a PAF tone you prefer the lower inductance such as the Chopper, but a higher inductance in parallel does a better single coil tone? I guess the higher inductance in parallel will have a higher resonant frequency than the lower inductance. Is the frequency doubled when you go from series to parallel? This one says alnico, they also have a ceramic version that's a bit cheaper. I think I remember you saying you preferred ceramic anyhow with these? (Thanks for the reply btw, I didn't get an email about it and am new to the forum. Now i've found the setting) > So if you're going for a PAF tone you prefer the lower inductance such as the Chopper, but a higher inductance in parallel does a better single coil tone? I guess the higher inductance in parallel will have a higher resonant frequency than the lower inductance. Yeah, for a PAF you want a final inductance around 4 to 5 henries, maybe 6 at the most, certainly not 8. For a good single coil tone, 2 to 3 henries. The problem is that no humbucker will do 4 to 5 in series, but 2 to 3 in parallel. A variable split is the best bet, or just buy one that prioritizes one sound or the other. > Is the frequency doubled when you go from series to parallel? The frequency doesn't double, because while the inductance drops to about a quarter of the series value, while the capacitance doubles. Interestingly, the parallel peak frequency is often very close to the split frequency. > This one says alnico, they also have a ceramic version that's a bit cheaper. I think I remember you saying you preferred ceramic anyhow with these? Yeah, ceramic is definitely better. I think it would be interesting to see neodymium magnets used in that type of pickup.
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Post by antigua on Dec 23, 2023 13:04:49 GMT -5
This is a question I could have posted in various places, so it’s not exactly specific to this set, but I’ve been meaning to ask: given most people set strat pickups higher on the treble side, why do “five-two” style strat pickups put the stronger alnico 5 magnets under the bass strings? According to their marketing, in order to soften the shrillness of the treble strings and increase the treble harmonics of the bass strings. IME most people set the pickups rather flat, Strats come that way from the factory most of the time. I think there's merit to it, the stronger magnetic pull induces more harmonics, and vice versa, in a way that's more interesting than what can be done with EQ alone. It's a pretty subtle difference though.
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Post by antigua on Dec 3, 2023 21:39:48 GMT -5
I was a little confused by this. You seem to say you prefer lower inductance rails, but you find higher inductance ones are more useful, and sound more like a single coil in parallel or split. So which do you really prefer? ;D Or am I misunderstanding. It depends on if you want it to sound best as a humbucking Fender single coil sound, or more like a Gibson PAF. There's no good way to get both, unless you take a lower inductance rail, inductance from 5 to 6 henries, and then partially split it with a trim pot in series with the wire that splits the pickup, so that it's not 100% split. I suspect the reason they make these rails often have a high inductance of 8 henries is because the bridge pickups are angled closer to the bridge in Strats and Teles, so even if they have the same inductance as a PAF clone, they sound brighter because of how they're angled. So maybe they lower the resonant peak even more just to offset that brightness. Even though the overall sound might make you think "Gibson humbucker", they lose the clarity of a real Gibson humbucker due to the lower resonant peak. So I prefer to have a rails pickup with the higher resonant peak, and just put up with the fact that the bridge pickup is closer to the bridge in a Strat or a Tele. I suspect that if you put a rails pickup in a Fender with straight aligned pickups, like a Jazzmaster or a Jaguar, it would sound more like a Gibson guitar without having to do anything special. Also curious if you've specifically tried the Fleor rails that seem most available on amazon right now. I've seen you say a few places that these cheapos are the perfect pickup. Makes me curious what is actually different about all the Dimarzio models when Fleor just gives you 3 different resistance levels to pick from. I don't think I tried Fleor specifically, but I've tried a few similar rail pickups in that price range. They're all the same layout as the DiMarzio style rails, but cost a fraction of the price. In general if rails pickups have a DC resistance of about 9k or less, they will sound thick and reasonably clear, like a PAF, and that tends to be called a "neck" pickup, so I'd use "neck" rails for all the positions, if I wanted the guitar to be versatile and not a shredding guitar. This one claims its DC resistance is 6k to 7k www.amazon.com/FLEOR-Alnico-Humbucker-Single-Coil-Sized-Pickup/dp/B09YCRHQ7Z/ref=sr_1_1?crid=O2LP6MJ696Z2&keywords=fleor%2Brails%2Bpickups&qid=1701657167&sprefix=fleor%2Brails%2Bpickup%2Caps%2C172&sr=8-1&th=1 , I'm interested in what the inductance of that pickup is, and how it sounds. Customers seem to be very satisfied. 6k to 7k, using the DiMarzio Chopper as a point of comparison, if theu use same size of wire, and I suspect they have to because of how small the coils are, then the inductance would be around 4 to 5 henries, and have a loaded resonant peak closer to 2.7kHz. It looks really promising.
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Post by antigua on Nov 13, 2023 2:02:24 GMT -5
Gibson recently made and sold 57 Classics, a PAF replica, with two cream bobbins. Since 1979 or so, DiMarzio has had a trademark on that color scheme for PAF replica pickups. In fact they even trademarked the letters "PAF", because they really wanted to make sure nobody mistook their intentions with these trademark applications. For the past forty years they would threaten legal action against pickup makers who made and sold this pickup in the U.S. And then out of nowhere, Gibson started selling this pickup, which they called "Double Classic White". How Gibson has done this without apparent worry of legal action from DiMarzio is anyone's guess. Although as of now this pickup is out of stock on Gibson's website and has been for a few months now, so it might not come back. I have two sets of double cream Donlis in two guitars, so I bought two of these 57 Classics in order to swap out in one of the two guitars, and get a little more variety between the two guitars. The marketing copy says www.gibson.com/en-US/Product/57-Classic-Exclusive/PU57DCW2 : Introduced in 1990, the '57 Classic provides warm, full tone with a balanced response, packing that classic Gibson Patent Applied For humbucker™ crunch. They are made to the same specs as the originals, including Alnico 2 magnets, nickel-plated pole pieces, nickel slugs, maple spacers, and vintage-style, two-conductor braided wiring. The ’57 Classic humbucker features balanced coils for a smoother, creamier tone and excellent hum cancelation. The pickups are also wax potted to remove all internal air space and any chance of microphonic feedback. Position: Any Magnet: Alnico 2 Wiring: 2-Conductor Cover: None Double Classic White Bobbins Wax Potted Average DC Resistance: 8K Details: Vintage vibes with rich, warm tones and balanced coils.I measured a 57 Classic a few years ago guitarnuts2.proboards.com/thread/7748/gibson-classic-stock-epiphone-humbucker , the values I measured this time are comparable. I measured the inductance at 1kHz in that old review, so the value there is different, but the DC resistance is right at 8k ohms. It kind of looks like Gibson decided the DC resistance should be 8k and left the other values up to chance. With an inductance of 4.8H, a loaded resonant peak of 2.6kHz and a DC resistance of 8k, it's more of a bride pickup in typical aftermarket humbucker language, but not such a high inductance that it's not good for the neck also. The capacitance reads high at 226pF, but that should really be ignored, there's nearly two feet of braded wire hanging off the pickup. The true capacitance is probably around 50pF, like most other PAF clones. Gibson Double Classic White - DC Resistance: 8.012K ohms - Q @1khz: 2.18 - Measured L: 4.819H - Calculated C: 225.6pF - Gauss: 350G (AlNiCo 2)
unloaded: dV: 6.6dB f: 4.89kHz (black) loaded (200k & 470pF): dV: 2.4dB f: 2.58kHz (blue)
I placed a Donlis beside the Gibson to compare the shades of cream, the Donlis has a more true cream shade, similar to the mounting rings you see on a Gibson or Epiphone Les Paul, where as the Gibson 57 Classic's bobbins have a more pinkish shade, but it's still plenty close.
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Post by antigua on Nov 13, 2023 1:37:58 GMT -5
I recently got ahold of an EMG-60, so I wanted to measure that response curve just to see how it compared with the 81 and 85. The EMG site www.emgpickups.com/60.html says The 60 humbucker packs plenty of output with a balance of thick, boosted mids, big lows and singing highs. Featuring close aperture coils, similar to a mini-humbucker, this model produces rich harmonic overtones. Due to its ceramic magnets, the EMG 60 has a full treble response and loads of output great for distinct single-note solos. The 60 provides clarity and character to your guitar and works very well in the neck position.
I haven't put this pickup into a guitar yet in order to hear it for myself, I have to rewire a whole Les Paul copy from passive to active value pots, so it's going to take a minute. The interesting thing is that it says it has close aperture coils, luckily I have magnet film on hand to "see" under the covers what they're talking about, it does look like maybe a Firebird sized humbucker is under the cover, centrally placed. I plotted the 60, 81 and 85 all at once. I have normalized the outputs: Based on the bode plot with the Ken Willmott integrator, all of them are very nearly the same, with the EMG 81 having more of a mid bump, and the 60 and 85 almost overlapping, except that the EMG-60 have a little more response in the treble. I think in practice these three pickups are effectively the same in terms of EQ, because the curves are so broad that a guitar amp's EQ three band EQ can probably approximate these differences, unlike a the more specific resonant cut-off of a passive pickup. Due to the high sensitivity of the output in relation to the placement of the exciter coil, I can't measure their relative outputs reliably, but overall they seem to all be about the same. According to EMG, the 81 and 85 supposedly had the same circuitry, and the main difference was that the 81 had a ceramic magnet, and the 85 an AlNiCo magnet. According to the copy, the EMG-60 has a ceramic magnet. In summary, if I had to guess what really sets the EMG-60 apart from the EMG-81, it's that it's using smaller Firebird-like coils, and the difference between the two of them with respect to the 85 is that the 85 has an AlNiCo magnet. I have a couple guitars with Firebird sized humbuckers, I have a Sheraton I with minis and a Sheraton II with full sized, almost the same guitar with these different sizes of humbuckers, and I do think the mini humbuckers sound more single-coil like in the timbre, with a sharper bridge sound a more chime-like neck sound. I'd expect the EMG-60 might sound a bit more single coil-like as well. This EMG-60 / EMG-81 set also happens to come with a polished nickel cover. This is the first time I've seen active pickups with a metal cover, but there doesn't appear to be any eddy current loading of consequence.
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Post by antigua on Oct 24, 2023 11:38:29 GMT -5
Ableton has a spectrum analyzer . You might have to try some different sound recordings to see the effect of the tone cap clearly, I think playing a single note in several octaves might work well, for example the high E and the low E at the same time, which should show a harmonic series in the output.
> Additonally, it is my understanding that there are different types of frequencies, so what would be the difference between sound frequencies and, lets say, simple harmonic motion frequency?
Sound is changes in air pressure happening at rates between 20Hz and 20kHz, which is the range detectable to ears, but realistically most people have an upper limit closer to 15kHz. Harmonics are fractions of a fundamental wavelength, so when you play a low E, the lowest frequency 82.4Hz is the fundamental, and then when you perform a pinch harmonic at the 12th fret, it divides the length in half, so you hear it's 1/2 harmonic that has a frequency of about 165Hz, double of 82.4Hz. If you pinch at the 7th fret, you divide the length by three, the frequency triples to 249Hz, and so on.
The thing to remember is that all of those harmonics can be heard when you pluck the string, but they're not all equally loud. So when you pluck the low E with a pick, you hear 83Hz, and 165Hz and 249Hz, and up and up, all at the same time. When you do a pinch harmonic at the 12th fret, you mute the fundamental of 83Hz, so all you hear is 165Hz and upwards, it essentially becomes the new fundamental note, and all the harmonics are now harmonics of 165Hz.
When you apply the tone cap to the circuit, what you're doing in effect is removing the harmonics from the output signal. If the cap rolls off all frequency beyond 1000Hz, then any harmonic above 1000Hz is removed from the sound output. The reason higher value tone caps make the guitar sound muddy is because the fundamental note all by itself, without any harmonic content mixed in, sounds "muddy", there's no treble in the sound, it's like the sound of the floor vibrating.
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Post by antigua on Sept 22, 2023 17:45:35 GMT -5
Hey, thanks for your reply, I really appreciate this. I used your reply to do my entire experiment, with a few minor changes. Firstly, the input jack method did not work, so instead I took apart the pick guard and soldered a wire on the tone caps. I then managed to "peek" out these wires for each tone cap so I could manually attach alligator clips to them and just swap out caps. Now, I do have a few questions. Firstly, I think a big mistake I did was I set the tone caps to 10 for all the experiments. Does this actually result in any perceived tone change or did I just waste my time? I can simply just swap out the cap values again because they're outside my guitar so it's no big deal, but I would prefer an explanation. Next, how do I keep this experiment as variable free as possible? I'm referring to the strumming. I tried to keep it as similar as possible but it's hardly precise. Lastly, how do I process the data and show mathematically that the produced sound is different? Does that involve frequencies or what. Any app a pro like you would recommend? Thank you very much for your help, and I hope you have the time to respond. If the tone control is set to 10, then you won't hear a difference with the tone cap. You hear the biggest difference at 0, all the way "down". If the tone control is not at zero, then you have some variable amount of resistance in between the pickup and the capacitor. Here are a couple plots that show the idea: this shows how the response changes with the tone knob: this shows how the response changes with the caps in parallel with the pickup, meaning the tone control is at zero: As you use higher value caps, you will hear the pronounced treble part of the signal move downwards in frequency, almost identical in sound to a wah wah pedal. When it comes to strumming, if you are recording the sound and comparing waveforms, then strumming is a big issue because you can hardly get a constant sound with a plectrum. It's really difficult even with a mechanical device. But if you are just listening with your ears, just strumming consistently is enough. In the same way that the sound difference of a wah wah pedal is obvious no matter how you strum, so will be the difference with various caps. Just for show, you can put a piece of tape on the guitar, and only strum the strings where that piece of tape is located. For the math, to show how the resonant peak changes, you take the inductance of the pickup (what kind of pickup is it?) , and then take your capacitance value and plug the values into here www.omnicalculator.com/physics/resonant-frequency-lc to get the resonant frequency. You just have to make sure you get the units right, henries for the inductance and microfarads for the capacitors, so that the peak frequency calculates correct. This ignores the pickup's capacitance and cable capacitance, but for demonstration purposes, you can just make a notes that you've ommited that, and omit it.
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