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Post by antigua on Sept 20, 2023 2:49:01 GMT -5
It blows my mind that there still aren't many USB oscilloscope options, let alone ones with bode plotting built in. Searching for "usb oscilloscope" and "bode plot" or "response curve" or "network analyzer", and some new stuff comes up, but it seems to generally be more expensive and not even as useful as what we had in the Velleman. The Syscomp CGR-101 was pretty good too for the price point, but they also stopped producing that. Aside from the Velleman and Syscomp, I've also tried using the Digilent Analog Discovery with the WaveForms software www.amazon.com/Analog-Discovery-Systems-Kit-Oscilloscope/dp/B07G8LG3JX/ref=sr_1_4?crid=WAE73A14ZRHJ&keywords=analog+discovery&qid=1695193508&s=industrial&sprefix=analog+discovery%2Cindustrial%2C123&sr=1-4&ufe=app_do%3Aamzn1.fos.c3015c4a-46bb-44b9-81a4-dc28e6d374b3 , and that is a really high quality hardware and software pair, but it was less useful to me, just because the Velleman software seemed almost purpose built for doing quick and dirty overlapping plots and labelling on the fly, so I could test lots of pickups in not a lot of time. The WaveForms software is very powerful and it can even do the response curve integration mathematically, but there's a learning curve to it, and it still not quite as convenient as the Velleman software was. I think with this and other USB oscilloscopes, it's going to be necessary to export the data, maybe a CSV, into Excel and manually graph the results. I'm thinking I might make a simple Javascript interface to allow several plot's worth of data to pasted in, and then presented with the Google Charts API and allow for some labelling, because what we really want to do most of time is compare two or more pickups, or compare the outcome after tweaking a pickup or a circuit. A few people use the Rightmark audio software and then test the pickups with their computer sound card. As far as I know, that works well and is potentially free, but since the Velleman worked so well for me, I didn't use that method. I think you have to wait a minute or two for it to perform the sweep, and then only after you can see what the outcome was, that process made it harder for me to correct errors in the test setup. There have been the Hantek and Picoscope USB oscilloscopes on the market for a few years and are still available, but they don't seem to have very full feature bode plot support in the software. I'm sure they offer a data export feature, which is probably the most I can hope for from these devices going forward.
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Post by antigua on Sept 15, 2023 9:43:22 GMT -5
Yesterday I had the privilege to work on some of Les Paul's personal pickups and one of his guitars. The guitar is a (most likely) 1954 Les Paul Custom previously owned by Les Paul himself. One of his crazy Frankenstein LPs. The pickups were also his, but I don't know if they were previously installed in this guitar or not. I had to design and make a mounting plate to work with the pickups as to not alter the guitar. I tested the pickups with my Integrator, and made some comparison plots. The Integrator I had set to 0db assuming that would be better for the low as hell impedance / low output pickups. The pickups are nearly flat across the audible spectrum, and pretty closely matched. Both are done with heavier gauge wire using scatter winds. I had to repair/replace the leads coming from the pickups. The following tests were done with my new leads connected: Ls @ 1kHz, Rd @ 1kHz, Cp @ 100kHz, Q @ 3kHz, 10kHz LP SB 1:
Ls 4.06 mH
Rd 4.0926 Ω
Cp Nope! (tried up to 200kHz, couldn't do it) Q @ 3kHz: 12.94 Q @ 10kHz: 12.13 LP SB 2:
Ls 3.8 mH
Rd 4.056 Ω
Cp Nope! (tried up to 200kHz, couldn't do it) Q @ 3kHz: 11.987 Q @ 10kHz: 12.26 Thanks for sharing this info. If someone wants to create replicas of these pickups, they can use this info. I see you have Ls at 1kHz, if your meter can do 100Hz, that's usually necessary for pickups with steel cores, because the eddy currents present a resistance, but since these are AlNiCo staples, the higher frequency probably didn't hurt too much in this case. I usually do Q at 1kHz just because there are times when 3kHz can approach the resonant peak of some high inductance pickups, but in this case that's a non issue of course. I'm surprised the capacitance didn't measure, but I'd guess it's because the pickup is of such a low impedance that it doesn't look capacitive to the meter. It's kind of funny that all that can be said about the resonant peak is that it's somewhere north of 100kHz. The loaded plot in this context is probably not too useful, since with low impedance pickups you'd use smaller pot values, but for all intents and purposes the response is flat, and only are not flat if you do like EMG or Fishman and attach a filter circuit to the pickup.
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Post by antigua on Aug 19, 2023 13:36:54 GMT -5
When I bought the set, they said it was AlNiCo 5. The gauss reading of 250G, which is more often associated with AlNiCo 5, but that's not a very reliable way of distinguishing AlNiCo bars in PAFs. It's a lot easier to tell the AlNiCo properties of single coils, because the difference in Q factor and gauss strength is immediately apparent, but with bar magnets, the Q factor and gauss strength barely changes at all from one to the next. If you for sure want a particular grade, it's probably easier to just buy the magnet and swap the magnets out. Also for AlNiCo 2 double cream, Gibson is now offering the 57 Classic in this color www.gibson.com/en-US/Product/57-Classic-Exclusive/PU57DCW2 there's a lot of talk on the forums about how they are doing this without getting sued by DiMarzio, whether there's a license deal or not. They're not as cheap as Donlis, but much of the purchase cost is retained in the value of name brand guitar parts. I just noticed under "bobbin" it says "AlNiCo 2", I didn't notice that before. Maybe Donlis' listing was messed up, but even if they claimed it were AlNiCo 2, I don't really trust that you would get AlNiCo 2. I'm impressed with what you get for the money, but assurance over the AlNiCo grade is not one of those assurances IMO. It's probably better to buy the magnets outright and swap them if you want to have certainty. Personally I think the magnet grade in PAF's is blown out of proportion, it makes a much bigger difference in Fender single coil type pickups.
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Post by antigua on Aug 14, 2023 19:25:53 GMT -5
If they are squealing, wax potting will work a lot better than taping the coils.
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Post by antigua on Aug 10, 2023 3:45:39 GMT -5
9k would usually indicate a hotter humbucker, but we don't know what gauge of wire they used. The one I measured showed 3.6H inductance for 7.4k DC resistance, by comparison an SD 59 measure 4.4H for 7.4k DC resistance, that's a much lower inductance for the same DC resistance, suggesting that there are fewer turns of wire on the FLEOR coils despite the higher DC resistances. If you measure 9k, I suspect it will end up sounding like an average PAF, and not an "overwound" one.
I hadn't heard of "white copper", apparently it's also called "cupronickel", but looking it up, it seems to be like something in between brass and nickel silver. Cupronickel has copper and nickel, which is like nickel silver without zinc. It's less conductive than brass, but more conductive than nickel silver. The proportions of metal in the alloys can vary though, knowing that Fleor is a budget Chinese pickup, it's usually safe to assume that they're putting cost before performance with their metal alloys.
For the base plate, the conductivity isn't really that important, it makes no audible difference in the resonance, especially with volume and tone control pot loads present. Some baseplates, I think from Fleor, were made of aluminum though, and that was bad if for no other reason than you can't solder anything to it.
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Post by antigua on Aug 8, 2023 18:38:19 GMT -5
I just wonder why a company that has been around for forty years would care about pickup analysis, ever so slightly at the twenty year mark, and then finally live by it at the forty year mark. Well there's nothing I can say about PRS that I haven't said before.
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Post by antigua on Jul 11, 2023 13:33:19 GMT -5
Thanks for sharing, that's interesting. It also just cool to see an electronic good being manufactured in America this day and age. They way they find the peak frequency is almost exactly how I used to do it, plug the exciter into a signal generator, turn the frequency up and watch the oscilloscope for the voltage peak, then just write down the frequency. I think the black box might just be putting a resistor across the pickup in order to measure the impedance, like this but in a shielded enclosure guitarnuts2.proboards.com/thread/7775/pickups-resonant-peak-usb-oscilliscope , I can't imagine what more would be required in between the pickup and the scope. Hearing him talk about AlNiCo from the perspective of a pickup mfg was interesting also. I'm glad to hear they take the details into consideration, although when it comes to actual production, it's hard to say whether or not that detail takes a back seat to cost efficiency. Would they order a special formulation of AlNiCo just to create a perfect Joe Bonamasa pickup replica? That strumming device looks well thought out, and I wonder why they do for the plectrum, because I made a setup similar to this, and I got a lot of variation in the outcome depending on the plectrum type and how it was attached to the arm. It's annoying to hear that they collect data such as inductance and Q factor but apparently refuse to share it. It just goes to show the adversarial relationship between the pickup makers and the customers which people have hated on me for in the past, but in both the case of PRS and Seymour Duncan, evidently they have the info, but put customers in a position of having to choose a product without the benefit of that info. I bet they would try to protect it as a trade secret if it were so trivial to gather with an LCR meter.
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Post by antigua on Jul 1, 2023 3:08:55 GMT -5
You'd probably want to put capacitors with value between 1nF and 100nF in parallel with the pickup to lower the frequency to an audible extent, as shown here www.buildyourguitar.com/resources/lemme/ down in the section titled "Altering Pickup Characteristics". Probably the most straight forward way to demonstrate for a school project would be to get assorted caps on Amazon, a couple alligator clip leads, a guitar and an amp. Then somehow expose the positive side of the circuit somehow, such as unscrewing the end of the guitar cable so that you can access the solder joints, then connect the alligator clips to the positive and ground of the guitar cable. If the guitar cable doesn't unscrew, on some guitars such as a Strat or a Les Paul, you can take out the screws holding the input jack into the guitar, pull it out and connect the alligator clips to the input jack of the guitar. When you hook up cap values such as 2nF, 10nF, 33nF and 47nF (or anything in between), with the alligator clips, putting the cap in parallel with the guitar, you should hear a distinct difference in the tone when the higher cap values causes the peak frequency of the pickup to drop. You can plug the guitar into the amp, turn it on, strum a few chords, change the cap, strum a few chords and show how the sound changes. This would work best with a Strat or Tele, because the Fender single coils tend to start with a high peak frequency which you can then drop down with caps. Guitars with humbuckers tend to have a lower frequency to begin with, so the caps make a difference but it's not as pronounced. That's a quick and dirty presentation, if you wanted to get sophisticated you could change the cap value with a dial or switches. If you want to show the actual plot, you could try using the Rightmark audio software and use a computer soundcard and a small exciter coil to make frequency plots without spending much money, but that might still be a lot of work.
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Post by antigua on Jun 29, 2023 13:44:31 GMT -5
The Filter'tron screws are definitely larger than the PAF screws, and that seems like a plausible reason for it to have stronger eddy current losses. The idea that the wider cross section causes a stronger eddy current roll-off seems plausible, but neither PAF or Filter'tron screw is as wide as the slugs in a PAF. I'll have to think of a good test to perform with some disposable humbuckers to get more clarity.
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Post by antigua on Jun 23, 2023 1:24:33 GMT -5
Here's a different question. I made a third pickup at the same time as those two, but it's much different. I'm guessing it's junk and I should salvage the reusable stuff, but please let me know if I'm wrong: This plot is funny. I was wondering for a second why there was a callout at 183Hz, and then I realized that was the peak Excel chose. 🤣 That double hump is odd. I see noise spikes at 120Hz, 180Hz and 300Hz, harmonics of 60Hz, so that must be AC mains noise. The double dip in the loaded plot is very strange, but I notice the second peak matches the frequency of the unloaded plot, which it makes me wonder if the wiring of the humbucker is/was messed up somehow, maybe one of the coils became shorted, something like that.
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Post by antigua on Jun 22, 2023 20:06:19 GMT -5
It's hard to compare the output amplitudes of pickups to a fine degree, because such a small variation in the driver coil distance from the pickup can impact it, but moreover the thickness of the bobbin can impact it, and would it be right to say a pickup has higher output just because it has a thinner bobbin? In any event, the difference of about 1dB is not perceptible. Personally I won't say it's perceptible until the difference is 3dB, and even then it can't be oversold, considering how much this difference is overshadowed but how near or far the pickup is mounted from the strings. To say a pickup is hotter seems to not just mean is has a higher output, but also features the the tonal difference of a lower resonant peak as well, and sometimes more the latter than the former.
One thing that would really help, if you can do this with Excel somehow, is show the dB difference, rather than the absolute value, for example, for the Yellow unloaded, the absolute difference of -4.60dB and -0.71dB is 3.89dB , so that's the overall amplitude increase at resonance, and that's good info to have when you're comparing pickups based on numbers alone.
The Yellow pickup has a very slightly higher unloaded Q factor, suggesting that the eddy current loss or DC resistance is slightly higher. The pickups are identical for all intents and purposes, though if one of them has a strong magnet, it will interact with the guitar strings differently at a given height.
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Post by antigua on Jun 21, 2023 15:08:14 GMT -5
That's a little abstract for me, but do you have any theory why the Filter'tron shows the effect so dramatically compared to the PAF type? They have the same overall layout, but the proportions of the parts are a lot different. IIRC, the filister screws are mostly what is responsible for the scoop, but it's not clear why the effect is much different as compared with APF screws and slugs. Are you sure it is the fillister screws? It makes more sense to me that the "scoop" (not part of the resonance) is caused by metal outside of the coil itself, such as a cover that can block signal at higher frequencies. I played around with a Filter'tron recently, and thought that it was the thick brass cover that did it. (Perhaps you made some measurements on a Filter'tron a while ago, but I did not find the discussion in order to review your results.) Yeah, this is an old test, there is no cover in this test, from here guitarnuts2.proboards.com/thread/7785/tv-jones-classics-analysis-review
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Post by antigua on Jun 21, 2023 12:36:11 GMT -5
I think I'm pretty close here with setting up my template: Can anybody tell me the point of the inductance test line? That doesn't represent the actual inductance. Is that used to calculate the inductance somehow? The inductance test plot is not really needed once you determine the inductance through one means or another, it's just for calculating the inductance of the pickup based on the resonant peak with a large know value for C, which is 4.7nF according to the schematic. Here's some javascript I for from chatgpt to do the work (and it seems to work): function calculateInductance(fr, C) {
let L = 1 / (4 * Math.PI**2 * fr**2 * C); // formula to calculate the inductance
return L;
}
let fr = 944.06; // Replace with the resonant frequency (in Hz) with known capacitance
let C = 4.7e-9; // Capacitance in Farads (4.7nF = 4.7e-9 F)
console.log(calculateInductance(fr, C)); // L = 6.047045154479244 henries
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Post by antigua on Jun 20, 2023 18:12:56 GMT -5
I would say that pretty well every pickup response can be considered as made up of two cascaded filter responses. There is a 2nd order low pass with some sort of a peak and also a more or less first order low pass shelf. The low pass shelf is caused by the eddy current losses and is essentially unaffected by loading. The 2nd order low pass is very much affected by loading. If the low pass shelf starts well before the 2nd order part starts a steep rise to the peak, the pickup will show the scoop in the response.
That's a little abstract for me, but do you have any theory why the Filter'tron shows the effect so dramatically compared to the PAF type? They have the same overall layout, but the proportions of the parts are a lot different. IIRC, the filister screws are mostly what is responsible for the scoop, but it's not clear why the effect is much different as compared with APF screws and slugs.
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Post by antigua on Jun 19, 2023 22:24:38 GMT -5
So now that we've got the above info, what is it telling me? Why do we want to compare the loaded and unloaded traces? What do you see when you look at the above plot? From the above plot I can see that the pickup would pair well with 500k pots, with the loaded peak only rising by about 2dB, and the loaded resonant frequency of 2.3kHz is sort of "hot PAF" territory for a humbucker, and if it's a single coil pickup, it's going to be a bold sounding pickup without much high end presence, like a hotter Tele bridge pickup or a hotter ceramic pickup from an import guitar. Most of the time, the overlapping plots are interesting when you have two pickup that are supposedly alike, but end up being different, and the overlapping plots show the extent to which they are different. Or less often, they're supposed to be different but are actually the same. The nice thing about the loaded and unloaded plot lines in one image is partly just that it keeps the data together in one place. The contrast between the two doesn't say much other than allow you to guess how much intrinsic capacitance is present, where the farther apart the frequencies are, the less capacitance there is. But there is something interesting about your plot with the loaded and unloaded in one view, the unloaded plot has a faint dip in output ahead of the resonant peak, but if you look at the loaded plot, that dip is not there. We see that dip with Filter'trons, and I'm still not entirely sure why it happens with Filter'trons and not with PAF style humbuckers (although it has been successfully modeled with LT spice as a three coil transformer, pickup, string and eddy current metal). To see that happen here adds a data point that might be useful later.
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Post by antigua on Jun 18, 2023 11:56:44 GMT -5
That's looking pretty good. Having them overlap in usually a must, because so many of these tests are comparing one thing to another. That's why I like the Velleman, even though it's crude, it doesn't require much work to create comparison plots. Only a few times have I had to take the screen shots and manually put them together with an image editing program. Another useful feature of the Velleman is overlaying text on the plot, so that if I only have the plot image, I can tell what pickup or test I was doing. I've found a lot of my own experiments with Google Images just going off of the text on the image itself. I could do all this with Photoshop, but that would increase the time required to test a given pickup and post the information by a lot.
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Post by antigua on Jun 9, 2023 14:12:48 GMT -5
That's true, most of the LCRs meters I have and have seen don't offer 3kHz, otherwise it might be a good test frequency for most pickups. I was able to use 1kHz effectively for telling apart nickel silver and brass covers. It seems to be useful when comparing pickups that are like for like. I can test at any of these points on my TH2830: 50Hz, 60Hz, 75Hz, 100Hz, 120Hz, 150Hz, 200Hz, 250Hz, 300Hz, 400Hz, 500Hz, 600Hz, 750Hz, 1kHz, 1.2kHz, 1.5kHz, 2kHz, 2.5kHz, 3kHz, 4kHz, 5kHz, 6kHz, 7.5kHz, 10kHz, 12kHz, 15kHz, 20kHz, 25kHz, 30kHz, 40kHz, 50kHz, 60kHz, 75kHz, 100kHz. If there are some other tests you'd like me to run, let me know. The Q value is mostly useful in situations where you have two pickups that look the same, but you're not sure if one has different metallurgy properties than the others, such as different covers or pole pole pieces (and probably not much else tbh), and the main reasons it matters in guitar pickups is because it's nice to know what the eddy current production is, or the type of pole pieces. If the eddy currents are high, it means the pickups will have a more aggressive roll off of treble. So the LCR meter subjects the pickup to the test frequency and causes eddy currents, and it causes an apparent resistance which lowers the Q factor. Generally, the lower the Q factor, the higher the conductivity of the metal, the more loss of high end. Also keeping in mind that the geometry of the metal will make a difference, because eddy currents are an electromagnetic effect: ... so measuring like for like pickups works out best, like Filter'tron to Filter'tron or Strat pickup to Strat pickup, but not Filter'tron to Strat pickup, because the different in physical geometry means that the Q factors will be different without necessarily saying much or anything about how the pickups will sound different, in this case because the Filter'tron's large steel filister screws are unique to that pickup. The two use main use cases I've tried to apply this to is telling apart nickel silver from brass covers with Tele an PAF style pickups, and the other is trying to figure out if a Strat pickup has AlNiCo 5 magnets, or AlNiCo 2 or 3 (which are very similar). I think 1kHz is a good one to test just because meters like DE-5000 and the Extech and in a lot of people's hands already, so they could compare notes, but 3kHz or 4kHz is good as a second or third value, because one you gather enough data you can probably start making new observations about pickups at this test frequency that have not been made before, but also as prices of LCR meters come down over time, 3 or 4 kHz Q measurements might become common place. I actually got a meter for Christmas that does arbitrary frequencies, but it cost around $300, and I'm hoping that meters of this sort will eventually fall below $100 so that more casual pickup enthusiasts can justify the purchase. On a similar note, you might want to measure C at two or three frequencies when you test, 50kHz, 60kHz, 75kHz and 100kHz, and make sure that they're all in agreement, because with a lot of pickups, I've found secondary resonances at higher frequencies, and if you happen to land on one, it will give you a bad reading. The secondary resonance appears to come from imperfections in the coil, that create a "coil with a coil" sort of formation, so they're common with hand guided Strat pickups, where the turns of wire are scattered about, but not at all common with machine wound pickups, which have more uniform layering of wire. Here's an example of a bode plot showing secondary resonances around 70kHz and 150kHz, so a test frequency close to those would give a bad capacitance reading, because the pickup is inductive at those frequencie, but at 40kHz or 100kHz it is capacitive and will give good values.
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Post by antigua on Jun 8, 2023 18:55:24 GMT -5
Antigua, I think Q should be measured at a higher frequency, such as three KHz, because this is in the range of frequencies that one hears as most affecting the brightness of the sound, and so the Q near that frequency is a good indication of the brightness that the pickup can produce. That's true, most of the LCRs meters I have and have seen don't offer 3kHz, otherwise it might be a good test frequency for most pickups. I was able to use 1kHz effectively for telling apart nickel silver and brass covers. It seems to be useful when comparing pickups that are like for like.
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Post by antigua on Jun 7, 2023 19:04:13 GMT -5
Fishman created this plot below in order to show potential customers how their Fluence model accurately modeled the EQ curve of vintage and active pickups... and interestingly if you see how the humbucker lands around 2kHz, and the Strat 3kHz to 4kHz, it's likely they used a 470pF load, or something close to it, otherwise the frequencies would have a larger spread. The Q factors depicted don't make sense though, under almost no circumstances will a Gibson type humbucker have a higher Q than a Strat pickup. In this case I don't think Fishman was trying to be informative so much as just provide evidence that they took a technical approach to recreating the voicing of passive pickup, probably the same in the case of PRS.
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Post by antigua on Jun 7, 2023 18:50:46 GMT -5
It's awesome that everybody here has a consistent comparison based on those arbitrary values, however... What about trying to compare to data from manufacturers? Are they adding the same, or some other arbitrary load, or testing the pickups directly? I ordered a board to make the Integrator because it looked like it would be entertaining, I'll see how the measurements look with it. From another post I made, I compared my direct to pickup measurements: Hemi Neck
Lace website: Resistance: 7.0k Peak Frequency: 2750 Inductance: 3.5 henries My TH2830 LCR: Ls: 3.69066H @ 100Hz Hemi Bridge
Lace website: Resistance: 10.0k Peak Frequency: 2600 Inductance: 4.6 henries My TH2830 LCR: Ls: 4.99706H @ 100Hz My measurements were series inductance at 100Hz with kelvin probes connected directly to the pickup. Other frequencies, or using parallel inductance didn't come nearly as close to Lace's measurements. I haven't seen many bode plots from manufacturers to compare with. Thanks, Josh I don't think arbitrary is the right word, it's more like a standard, and standards are often arbitrary, but the fact of them being a standard is more meaningful than the fact of if being arbitrary, like the precise length of a foot in the English system... who's foot? The 470pF capacitive load was previously used by Helmuth Lemme as far back as 2009. I'm sure 470pF was chosen because it's a standard cap value that comes close to a 10 to 15 foot guitar cable, which is a typical length. As far as pickup manufacturers go, it seems clear that they prefer to just sell pickups based on description of how the pickup might sound in your guitar. About the most they provide spec-wise is DC resistance and in a few cases, inductance. I suppose a lot of guitarists wouldn't understand what a bode plot is, but speaker manufacturers like Celestion and Jensen provide lots of specs and plots. If ever there was evidence that there is a lot of snake oil in how pickups are marketed, that would be it, IMO. Fender provides inductance values for a lot of their pickups, but often the values they state are flat out wrong, suggesting inductance values that aren't believable for a given pickup. In the case of Lace, if they don't tell us how they measured the inductance, we can't know, so it just has to be regarded as semi-reliable information. Your inductance measurements don't seem to be overly deviated from Lace's, looks like its within 10%
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Post by antigua on Jun 6, 2023 17:18:28 GMT -5
Hi, I recently got into messing with (making) pickups. I've read up quite a bit about how people are testing, and adding things in to make their measurements appear "more realistic." That's where the whole thing seems messed up to me. The first problem is that that test rig will never exactly match every guitar, so what's the point? It seems to me like it's just skewing the numbers arbitrarily. The second problem is that measuring any DUT is already modifying the DUT. Adding arbitrary values via another DUT to the original DUT doesn't guarantee realistic comparisons, it simply requires you to continue using those same modifications to make future comparisons. There are usually two measurements, loaded and unloaded, loaded is with 470pF and 200k ohms parallel added, and unloaded is measured without anything added. I guess you're saying that 470pF and 200k are arbitrary, it is, but what matters is that it's consistent. The 200k resistance is lower than with a Les Paul of two 500k pots, and lower than a Strat or Tele with two 250k pots (when a single pickup is selected that also has a tone control), so as said, you can sort of mentally adjust the values based on the guitar you plan to use. So if you see a Q factor of "2", you know that in a Gibson it will be a little higher, and in a Fender it will be a little lower. The 470pF represents a guitar cable, and of course they come in all lengths, so you have to look at the outcome, suppose it's 3kHz, you have to think of it as a range, where a lower C cable will get you maybe 3.3kHz and a really long cable can drop it way down to 2kHz, but at least you know when comparing pickups that there's a 470pF baseline. One of the problems of using a real pick guard to test is that potentiometers are notorious for having imprecise resistances, they tend to be up to 10% off of the nominal value. And of course, you'd have to use a real guitar cable, and there again, there's probably no good candidates for a "standard guitar cable", even if you suppose a standard 10 foot length, the capacitance per foot for guitar cables varies by a lot. So maybe what has gone unsaid is that even when two guitarists compare the same pickups, they're hearing something very different from one another, but when people talk about what they hear, it's all very subjective, and at best you get an average consensus. There's still a lot of interesting observations to come out of it though, like why is a JB called a bright pickups by so many guitarists, even though it has a loaded peak of 2kHz? Why is a Little '59 described as being "PAF-like" if it has a resonant peak that is 1kHz below that of a typical PAF clone? I'm happy to say that we've gathered so much information in the past few years that lots of hypothesis can be made about these things, where it wasn't possible before due to a lack of data to draw from.
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Post by antigua on Jun 6, 2023 16:14:26 GMT -5
I have a nice Siglent scope (SDS2X04XP) with a built in AWG, and bode plotting. I'm new to testing pickups, so I'd love some feedback to see if I'm setting this up correctly, or if there's something I need to change. Here's how I set it up comparing it to your bode plots: Here's the results on a Lace Hemi Bridge pickup: I also tested that pickup on my TH2830 bench LCR meter: Lp: 5.79834H Rd (DCR): 10.2243KΩ Cp: 147.358pF Cs: 148.069pF Q Factor: 2.49549 (Is this useful?) Q, L, R @ 1kHz C @ 100kHz Thanks, Josh That's a nice looking device. Measuring Q at 1kHz is good because it's below the resonant peak but high enough to cause eddy current losses, but the L and R are better measured at 100Hz in order to reduce eddy current losses in the calculation made by the meter, and you want it in series also, to tell the meter that the resistance it sees is in series with the inductor. For capacitance it's the opposite, the capacitance is in parallel with the resistance, and you choose a high frequency in order to not only measure above the pickup's resonant peak, but to maximize the capacitive effects over the inductive and resistive. I've never measured a Lace Hemi, so I can't compare, but I suspect the values will be somewhat different if you measure series at 100Hz.
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Post by antigua on May 4, 2023 10:56:44 GMT -5
The purpose of the conductive shield is to be a direct path to ground for capacitively coupled noise, so all that is required is that it have low resistance relative the overall circuit impedance. For magnetically inducted noise, the permeability, conductivity and thickness factor into how much dissipation occurs, so the metal allow would matter a lot more in that case, but the audio frequency noise is low frequency, so the metal would have to be thick, and would block out the guitar string signal if it were in between, and this is the kind of noise that humbucking addresses anyhow. I guess humbucking doesn't address capacitive noise because it will hit one coil more than the other most of the time, but that's just a guess, I'm fuzzy on that.
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Post by antigua on May 3, 2023 19:19:56 GMT -5
I gave it a try, I loaded this video on my phone and held the speaker up to the pickups, and observed the difference between series / parallel, as well as neck and bridge pickups having different inductances, and wow, you can hear the difference, plain as day. You can hear the resonant cut off very clear, similar to when you cup your hands over your ears. It seems like a easy way to determine if neck and bridge models are much different without need a multimeter to measure DC resistance. It's all around good way to get a specific read on the resonant peak of a pickup without any special equipment aside from a phone and YouTube video. If a person did this a lot they might develop the ability to guestimate the resonant peak by ear alone.
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Post by antigua on May 3, 2023 11:59:21 GMT -5
The same spurious confidence and lack of any understanding. I wonder where the idea of power lines being a source of high frequency noise comes from, and also a sheet constituting a cage.
Neither of the systems has picked up the difference between electric and magnetic sources of interference.
This is probably an unfair test. There are other systems of this sort that are trained on scientific data; presumably one of those could give a better answer.
To kind of cut to the chase though, is it simply true that if guitar pickups were intended to receive RF instead of audio range, that the ratio of noise blocking provided by conductive shielding would be higher than it is? I think the question that drives people mad, even if they don't know it, is why conductive shielding is so important in various electrical applications, but not with electric guitar. I know that per FCC regulation, part of the purpose of the shielding is to prevent an electrical device from emitting noise, and becoming an EMI/RFI pollution source. Could it be that shielding is meant to keep the noise in, more so than block noise out, and so the shielding is added expecting it to do reduce noise, when we're really just making our guitars more FCC compliant? As for ChatGPT predicting the next word, I think it's more complicated than that, it weights importance/relevance of ideas, like it takes in a sentence and algorithmically cuts it up in order to find the important parts, so a lot of the mistakes I've seen it make seem to be related to me asking it one thing, and it thinking I want or need to know something else. Like I ask it about humbucking versus shielding, but it doesn't understand why that's important, so it takes related ideas that are deemed important otherwise, and presents that instead. I've seen people get the info they need by just changing the way they ask the question, because doing so gives the AI model a different clue as to what information is important to you.
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Post by antigua on May 2, 2023 22:14:11 GMT -5
While experimenting for different tones, I've had the guts of working guitars laid out on the table. I've enclosed the guts in a Faraday cage, and compared the noise when the cage is grounded versus when it's ungrounded, and I can definitely hear a difference. I don't have any absolute measurements, but toiling for long periods with the guitar's innards on the table, grounding the cage and reducing the noise makes life a little more bearable. The only refinements I can offer on my observations: -the noises reduced by shielding seem higher in frequency when compared to the noise that's reduced by humbucking -the amount of reduction by shielding seems less than the amount of reduction by humbucking That's good to know, although I've had unexpected things happen when the wiring was external to the guitar, when there's more distance between the components. I know that when I test my wiring changes with alligator clips for example, it seems much noisier than when it's all soldered down and closed up, even when the guitar in question has no shielding.
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Post by antigua on May 2, 2023 19:37:55 GMT -5
My understanding to date has been that humbucking blocks alternating magnetic field noise, where as conductive shielding blocks noise that arrives in a capacitive manner, an alternating electric charge that causes unwanted voltage interaction with the pickup. But my understanding of this is still somewhat loose. So I tried asking ChatGPT version 4, to see what sort of answer it would give, and this is what it spit out:
what is the difference between the type of noise that is blocked by humbucking versus the type that is blocked by conductive shielding?
ChatGPT
Humbucking pickups and conductive shielding are both used to reduce noise interference in electric guitars and other instruments, but they target different types of noise.
Humbucking pickups: Humbucking pickups are designed to eliminate or "buck" hum caused by electromagnetic interference (EMI), specifically the 50/60 Hz hum that comes from power lines, transformers, and other electrical sources. This type of noise is also called "single-coil hum," as it mainly affects single-coil pickups. Humbuckers use two coils with opposite polarity and wound in opposite directions. The hum picked up by each coil is out of phase with the other, so when the signals from both coils are combined, the hum is canceled out, while the desired guitar signal is preserved.
Conductive shielding: Conductive shielding is used to protect against radio frequency interference (RFI) and other high-frequency electromagnetic noise. This type of noise can come from various sources, such as radio stations, Wi-Fi routers, cell phones, and fluorescent lights. Conductive shielding involves enclosing the electronic components, such as the pickups, control cavities, and output jack, in a conductive material like copper or aluminum foil. The shielding creates a Faraday cage that prevents high-frequency noise from entering the electronic components, thus reducing interference.
In summary, humbucking pickups are designed to eliminate low-frequency electromagnetic interference (EMI), specifically the 50/60 Hz hum, while conductive shielding is used to protect against high-frequency radio frequency interference (RFI) and other electromagnetic noise sources. Both techniques can be used together for comprehensive noise reduction in electric guitars and other instruments.
I've seen ChatGPT be wrong about all sorts of things, so I'm not implying what it's saying here must be correct, but it seems to basically be saying that the conductive shielding differs from humbucking in that it target high frequencies. It seems that humbucking works a lot better than shielding in the electric guitar context, is this simply because humbucking is more effective in the audio range, while conductive shielding is more effective in the high frequency range? The capacitance across the guitar's circuit is obviously high enough that audible sound is rolled off, let's say around 3kHz to 4kHz, isn't that filtering action grounding out high frequency noise, even if the shielding is omitted, or fails to block the noise?
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Post by antigua on May 2, 2023 15:10:30 GMT -5
Surprisingly, the 10k Lil' killer he got had an unusual freq response when tested with white noise through an earbud. As I recall, holding the earbud over one blade had a much higher freq, yet lower level, peak than the other. Using my 160pF cable and the earbud between both blades, the peak centered between 4-4.5kHz with an extended high freq shelf below the peak. I haven't seen that in any other pickups I've tested. Incidentally, the other two pickups had peaks very close to that one. That's a cool idea to test the pickups with a white noise signal. I suppose you were using an audio program to get a frequency measurement, but I wonder if white noise into the pickup would make it's EQ profile audible to the ear, especially if you have bridge and neck pickups that are different inductances. It's often hard to compare them in situ because they're in different positions of the guitar. I'll have to give that a try later.
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Post by antigua on May 1, 2023 19:35:56 GMT -5
If the DC resistance of the Lil Killers are 6k and 10k and wired in series, then it sounds like they probably have inductances in the range of steel poled Strat pickups, 3H to 4H, but they sound like they were made "Stratty" where as the Vintage Rails and Duckbuckers seem to be Cool Rails or a Little '59 just wired in parallel instead of series. It's a waste of wire to design a humbucker that is meant to be wired in parallel, because get the same end result by using less wire and connecting them in series, but Seymour Duncan probably has a marginal cost on a coil that is used for multiple pickups. I like the Vintage Rails in my Fender Aerodyne, they're modern looking pickups for a modern looking Strat. I added a little push toggle, similar looking to the button on the Deluxe Strat, that gives me B+N and B+M+N. I played 90's rock with this guitar for about an hour with a drummer, I actually ended up using the bridge in series a lot, because in parallel it's a mighty thin tone, when you need some creamy power chords, the series mode is very good to have, but the clean parallel bridge tone with the tone rolled down a way sounds really awesome, very vintage, like how Strats were often heard in the 50's. I also used the neck in series a few times, to get more of a piano like bang out of it, still rather clear. I like how the dramatic drop of the resonant peak between series and parallel really changes the overall voice of the pickups quite a bit. The pole pieces don't have to line up with the string because the magnetic fields are not that focused for one thing. The neighobring pole pieces also slightly magnetize the stings also, so you would get more of a drop if the string were on the outside of the pole piece, where there is no neighbor. That's why you can perform string bends with virtually no drop in volume, but in the special case where the pole pieces are of different polarizations, there is instead a dramatic drop in output when you bend the string in between the pole pieces. The Seymour Duncan single coil sized humbuckers all have the same pole piece spacing, no matter if it's a neck or bridge model, so if you were to buy three bridge pickups and use them as a set you'd have the same string alignment situation with that guitar.
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Post by antigua on May 1, 2023 1:10:48 GMT -5
I love the look of that guitar, with the black and pearl. The sophisticated look of the pickups goes well with the sophisticated look of the toggle switches. It looks like a guitar that could land on the moon. Also that's cool that you diagram it all out, with good looking graphics.
I'm a little surprised you didn't hear a difference between parallel and split, because you really hear a difference with full sized humbuckers. This is an educational experiment though, because it goes to show that the reason split and parallel is because you have two coils reading the strings instead of one, but in this case the two coils are so close together that it doesn't matter, they're effectively reading the same harmonics from the string, and this is further proof that a single coil sized humbucker doesn't have the potential to sound like a full sized humbucker.
When the humbuckers are split, you have half the inductance about about double the capacitance as compared to series, but in parallel you have about a quarter the inductance and quadruple capacitance, so the proportions of L and C get re-arranged, but the resonant peak ends up remaining nearly the same, although the impedance changes a bit for each wiring mode, similar to how it is speakers are wired in series or parallel.
Tonight I finished putting Vintage Rails into the blue guitar that originally had the Duckbuckers, and I wired it the same way with three push pull pots, parallel down series up. It's a bit like having the same guitar twice, but they look and feel different. An mildly interesting difference between Vintage Rails and Duckbuckers is that Vintage Rails like a second order harmonic because the string vibrates across a magnetically homogenous "rail", where as with a Duckbucker and all other pickups with discrete pole pieces, the reluctance increases and decreases as it passes across the pole piece, but that second order harmonics which is caused by that fact is very faint and doesn't really have any impact on the sound. I think the stronger magnetic field afforded by the more solid metal of the "rail" makes a bigger difference in how they sound.
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