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Post by stratotarts on May 2, 2021 16:05:20 GMT -5
Specs can also be used to baffle brains... you mentioned something there that reminded me of that right away - I've seen the resonant peak given as a specification. By itself, unloaded resonant peak frequency is a relatively unimportant spec because of the fact that it is mainly influenced by inductance and capacitance, inductance is not altered by the guitar circuit very much but capacitance definitely is. But the capacitance is always significantly overshadowed by the guitar circuit capacitance. Hence inductance by itself, although it is a much simpler data point, is a far more revealing aspect that tells you far more about how it will operate in situ than resonant frequency ever will. But it sounds really knowledgeable and technical so someone can pretend to be giving out specs when in fact almost nothing useful can be learned from it.
If there is ever a useful "lingua franca" that everyone could use to characterize pickups technically, besides the general construction and type, it would be inductance, loaded resonant frequency and loaded Q. A standard load doesn't exist in the industry, around here we kind of settled on 200k/470pF because it's pretty close to most guitar circuits. That would be a problem in an industry that has no governing body or professional association to organize standards (such as IEEE). It's the 2 dimensional map produced by loaded resonant frequency and Q that mainly defines pickup tone differences. Most other specifications and details are inputs into those characteristics. Thus there are often many ways to target the same data point in that space.
But it would be a huge step, really the first step, if manufacturers would begin listing the inductance and preferably also the frequency at which that is measured (ideally 100/120 Hz, whichever doesn't pick up line noise 50/60 Hz in their country).
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Post by stratotarts on May 1, 2021 20:58:07 GMT -5
There can never be too many testers. Also robust discussions have not generated a "right way" to test. Instead, a field consisting of different programs and investigative focii has evolved. It is like a smorgasbord of concepts and techniques that you can use. When I started my investigations in 2014, it was apparent that such work existed, but was fairly rare and isolated (meaning not much feedback and interaction amongst researchers), also scantily published. Here we are in 2021 and I see a tremendous interest in the subject, not just from people approaching it from technical interest or curiousity, but also from pickup manufacturers. I never reveal any specific information about individual customers, but I can tell you that many commercial pickup makers now have my device. In my conversations with them, it's clear to me that they accept the validity of the tests and want to engage in the technical aspects of testing that will assist them in design and manufacturing. Before my device came along, some of the big ones had the Lemme integrator. I've seen one in a published photo taken on a factory tour.
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Post by stratotarts on May 1, 2021 20:40:08 GMT -5
Yes, it all makes sense. The area directly between the poles and strings is particularly sensitive to differences because it is where the time varying magnetic field from the string is concentrated. So while metallic differences make a difference anywhere in the pickup, that difference is usually quite small unless it is actually near the string field. It is only the magnitude of the difference that surprises me a little bit here. But all plating is not equal. Since your samples come (I assume) from completely different supply chains, one can not perfectly eliminate certain variables. The "unplated nickle silver" vs. "nickel plated nickel silver" may not be a clear look at the plating, due to the fact that each German silver base material might not be the same. Of course, the only place you could really do a perfectly clean test would be in a factory, or to plate them yourself. So it's still interesting to make close comparisons.
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Post by stratotarts on May 1, 2021 20:30:56 GMT -5
Another thing about the stock inductors - I haven't cracked one open yet, but it's likely to have a bit of potting and case plastic between the outside surface and the inductor core. That should help isolate it magnetically also. I bought some smaller inductors to test, but I've been swamped and haven't had time. I did get a chance to measure my "standard coil" - 50 turns on a humbucker bobbin. I came up with 105 uH and 24nF, which if I'm not mistaken would make it resonate around 32 kHz. I'm also too swamped to test that directly. If that is the case, I would consider it too close to the upper end of the audio test range to increase the number of turns very much. That is with AWG#30 wire, I previously used #26 and I didn't have a chance to measure that. But it's probably not far off. At the moment there is plenty of headroom for testing, I usually use the low gain setting on the integrator and if I need more, I can just flip the switch and add 20dB.
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Post by stratotarts on Apr 25, 2021 8:05:46 GMT -5
I notice that the additional clearance needed for tall bobbins, compared with the steel pole version, comes from the absence of permanent bar magnets and screw retainer bar. In spite of that, they also appear deeper, as the cover seems to not extend all the way to the bottom. Am I right about that?
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Post by stratotarts on Apr 20, 2021 16:40:46 GMT -5
When things like this happen, there are so many real world variables that can enter into it, it's hard to troubleshoot remotely because I can't see your exact setup. First of all you should check and re-check your connections. If that all looks good, you might check resistance values. Sometimes resistors get mixed up, and the manufacturers can't agree on paint colours which breaks the resistor colour code. Often orange and red get mixed up, red is painted with an orange-y red, or orange is painted with a reddish orange. Best to check values with a DMM. Any capacitors should have the value checked. Check your ground connections and make sure they're not reversed.
Honestly, the best thing would be if you could post images...
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Post by stratotarts on Mar 30, 2021 9:26:36 GMT -5
Isn't there a risk that the potted inductor's permeability will interfere with the measurement? Generally, there could be, since inductors are constructed with different core materials. But this type uses a ferrite core, which has an exceedingly high permeability and so is effectively transparent as far as the measurement is concerned. I also A/B tested it with a full sized air-core test coil using the same pickup. The alignment of results was almost perfect, I can't find the plots right now because of all the PC swapping around I had to do recently. As I recall, as near perfect as two consecutive plots using the same test coil.
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Post by stratotarts on Mar 29, 2021 22:35:56 GMT -5
More on the wind count later, but I am now building exciters based on off the shelf potted inductors such as this one:
I can buy these components inexpensively at the local electronics store. There is a 100 ohm resistor in series under the shrink wrap tubing. The ruler shows centimeters.
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Post by stratotarts on Mar 27, 2021 12:36:38 GMT -5
The demand for test coils increased enough to make it important for me to refine the assembly techniques a bit. I realized that it was an opportunity to document it for anyone who wants to build one themselves. I was going to attach the document but it seems not to work for some reason. So I will just post a link to the file:
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Post by stratotarts on Mar 7, 2021 10:19:21 GMT -5
Cool and interesting. I wondered about the aluminum pickguard on my Squire Jazzmaster, no time to look into that yet. I can't see the whole process for your slot cutting, but it appears that you are using the humbucker slot configuration, that's not quite right for the single coil. Although the slots across the top probably do provide some improvement, the really effective cuts have to extend from the center line across the poles, longitudinally across (so half of the slots that you have cut there) and completely down one side. If the sides are not cut, the sides of the cover become an active circuit.
Secondly, it might be a sacrilege with such a nicely decorated pickguard, but you could also slot it with a small cut between the pickup and the neck, right in front of the truss rod adjustment screw.
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Post by stratotarts on Sept 15, 2020 20:09:36 GMT -5
All the very first pickup coils had thick wire by modern standards. I wonder if the underwound aspect was somewhat compensated for by (I'm guessing here) a low resistance volume pot, maybe no tone pot? Into a very high impedance vacuum tube input. Then the amp itself probably had very low cutoff frequency for its working bandwidth. I think the simple amp tone circuit from back then was practically the same as the guitar one. A jazz player would dial it down.
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Post by stratotarts on Sept 15, 2020 19:50:45 GMT -5
That's great news, I thought right away I would even purchase a hard cover, but I couldn't make out how to do that on the German order page. Actually, I would purchase an ebook if there was a way. I guess it will take some time for all the options to be available.
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Post by stratotarts on Jun 29, 2020 9:53:50 GMT -5
Note that the degaussed A5 did not change in the direction that would make them similar to the other alloys. So, if anyone suggests that degaussed A5 is an alternative to A2 or something, they would be wrong.
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Post by stratotarts on Jun 3, 2020 21:58:57 GMT -5
In the frequency domain: There are three recognizable regions of the pickup response - the low end which is always extremely "flat", the peak which depends not only on pickup construction but damping, and the rolloff which is a natural result of the RLC response of the pickup. To your question, the low end is both theoretically and practically linear, to the point where it can be taken as a reference level. When I plot various pickups, the expected level between 100Hz and just before the pickup resonance, is less than 0.5 dB or so.
The amplitude of the resonant peak, compared with the rest of the signal, can be tweaked as desired in various circuits and guitars.
In the time domain: Have any practical experiments been done? I don't know. But consider that the result of non-linearity would definitely be visible in the frequency domain also, because of the presence of harmonic overtones indicating distortion. But those typically haven't been noticed.
The hysteresis part you might explain further, as it is mostly believed that the threshold of any magnetic hysteresis is far greater than any string signal. That is based on existing measurements of magnetic hysteresis of materials that designers use for many purposes besides this one.
It's actually a simple test that you could do - inject a clean fundamental sine wave with an exciter coil. Look for harmonics. Try a few frequencies and plot if desired. But I don't think you'll actually see much there.
Further, there may be a distinction between hysteresis and non-linearity, however in practice hysteresis inevitably introduces non-linearity and therefore harmonics in the frequency domain.
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EMG-81
Mar 8, 2020 15:25:46 GMT -5
Post by stratotarts on Mar 8, 2020 15:25:46 GMT -5
Yes, it's due to the smallish capacitor values between the coil and the op amp input inside the pickup (input DC blocking capacitor). It's unlikely to be a design mistake, someone thought it sounded good.
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Post by stratotarts on Feb 25, 2020 12:10:44 GMT -5
What are the coils wound on? Directly on the magnets, or are there bobbins?
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Post by stratotarts on Feb 7, 2020 15:12:04 GMT -5
I have seen this strat pickup with copper taper shielding below the fiber plate. DO you have any experience about this? Will this be a good shielding practice? I think this will make the polepieces connected to the ground. Will it introduce Eddy Currents that might affect the tone? thanks! I haven't seen it on a Strat before. It seems like a good idea. It will not introduce significant eddy currents because it is distant from the string field, and not relatively very conductive because of the thin-ness of the copper tape. Even when a coil is wrapped externally with copper tape, the losses are not huge (although in that case, they may be considered significant, e.g. a few dB).
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Post by stratotarts on Jan 12, 2020 8:08:46 GMT -5
The pole pieces having reversed polarities on each side of the pickup, three north and three south, which isn't actually necessary since there are no "in between" positions. You only need reverse magnetic phase when any given string is sense by two pickups, but with the pre-wired pick guard, every string is sensed by one pickup at a time, in all five positions, so all that is required is reverse phase, but the reverse polarity could be ignored. Sorry, you lost me there. If you select a single pickup by itself, don't you need both magnetic polarities to make it hum canceling? Or, wouldn't you want to have a choice of using a single pickup?
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Post by stratotarts on Jan 12, 2020 8:00:46 GMT -5
Thanks for sharing!
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Post by stratotarts on Jan 7, 2020 18:25:00 GMT -5
The theoretical amplitude of a harmonic of a square wave is 1/n times the amplitude of the fundamental where n is the order of the harmonic. Hope this helps...
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Post by stratotarts on Jan 7, 2020 18:15:33 GMT -5
Interesting, I always speculated that all the chrome P90 covers were chromed plastic. I guess that is just a modern thing. Certainly those wouldn't be as durable, so cream or black makes sense. The 6-slotted mod would work on the metal covers, I'm not sure how ugly that would make them though...
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Post by stratotarts on Jan 5, 2020 10:14:15 GMT -5
The latest suggestion for shielding SCs seems to be foil with a gap ...
Re cavity shielding, there are a small number of youtube vids that include before and after recordings and do show less noise after .. albeit much smaller than the number of people showing 'how to shield' but including no evidence of whether it made any difference or not. OTOH I don't know of any vids that have before and after recordings that show no noise difference (perhaps there are some people who found that ... but they were too embarrassed to show they wasted their time !?).
Not sure if Wacker got the gap idea from me (since I published information about gapping in 2014 here: link . However, I found in that situation, that presence of the gap introduced only a 0.5dB difference in the peak response. Strat pickups have a plastic cover - I wonder if anyone has ever tried shielding the inside of those?
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Post by stratotarts on Jan 5, 2020 9:53:39 GMT -5
The downshift of the peak with the tone capacitor can justify having a guitar mounted tone control - the interaction of the tone circuit with the pickup is unlike the independently responsive tone controls of the amp. Of course, nowadays an inline equalizer can also do almost anything tonally, if the amp doesn't already cover it. However, that requires a lot of knob twiddling. As the tone volume control resistance decreases when it is turned down, the Q also increases as the resonant frequency drops. It's just serendipity that such a simple circuit also happens to have a sonically useful response.
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Post by stratotarts on Dec 26, 2019 19:04:48 GMT -5
Apart from that, I think that there are other reasons for using a different kind of soldering tool. These guns have very poor temperature regulation, tending to run hot. This often creates excessive oxidation on the tip, which makes it difficult to maintain a clean tip, and also contributes to improper flux activation at the target join. The low mass of the tip also allows the temperature to drop rapidly when touching a larger join, which can only be counteracted with more "juice" at the trigger. That makes it harder to control. Altogether, it means that it's not really well suited to finer electronics work.
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Post by stratotarts on Dec 22, 2019 8:16:53 GMT -5
I'm surprised at how much of a drop in inductance the Super Distortion (as the Dual Sound) gets when switched to parallel. Inductance is doubled with coils in series, halved with coils in parallel. So the ratio between the two configurations is 4:1.
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Post by stratotarts on Dec 1, 2019 8:28:21 GMT -5
I did let the coil cool to room temperature before doing any readings, backed up by checking to see that DCR returned to the original reading, so I wonder if Q did in fact change as potting time rose. The Q factor is determined by the real / resistive portion of the impedance. Changes in L or C will move the peak frequency, but not the Q factor. If the resistance is unchanged, then the Q factor must also be unchanged. That is true of a fixed ratio of L/C, but not a change in C, as: A higher value of C results in a lower value of Q if L remains the same.
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Post by stratotarts on Dec 1, 2019 8:16:29 GMT -5
Using a rectangular coil inductance calculator, I get the result that if the coil width increased from 8mm to 9mm without any change in area, the length would have to shrink from 50 to 44.45mm and the inductance would increase by 3.3%. I'm assuming that the coil can't stretch overall very much due to the relatively high tensile strength of copper. This is another reason why I don't think the temperature could have affected the results very much.
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Post by stratotarts on Nov 30, 2019 22:45:59 GMT -5
Thanks, I was wondering how that test was performed. BTW, many people caution against going over about 150 degrees fahrenheit during potting or risk deformation of the bobbin. Are you aware of this and is it possible to see if any occurred? The reason I bring it up is that I'm wondering if it could conceivably change the physical dimensions of the coil in a way that might affect results. Perhaps not so much of a risk in a Strat style bobbin as with a Humbucker, and perhaps also I'm splitting hairs a bit too finely. I think the resistance measurements show that this didn't happen. If the coil was stretched, the resistance would increase. BTW I potted with 80/20 paraffin/beeswax at about 180. It's true some plastics shouldn't get too hot.
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Post by stratotarts on Nov 29, 2019 18:56:33 GMT -5
One thing I overlooked - an unpotted coil doesn't just have an air dielectric. It has the insulation as a dielectric. Perhaps this would explain the lack of doubling, as there would be some increase in C vs bare wire, right from the start. It looks like common magnet wire insulation materials also are in the 2-3.0 range of permittivity (but enamel is very high at around 5.0... hmmmm).
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Post by stratotarts on Nov 29, 2019 11:06:34 GMT -5
At what test frequency are you measuring capacitance with the Extech? Should be 100kHz. It's interesting to compare the results with pure theory as C is proportional to the permittivity of the dielectric. As an ideal capacitor, the wax vs. air difference in permittivity should be the same as the difference in C - hence capacitance should more than double with wax.
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