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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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Post by stratotarts on Nov 28, 2019 22:19:24 GMT -5
It is not my intention to quarrel, in fact I welcome you to this venue and assure you that your contribution is valued. Especially as it hasn't been presented here before. As a longtime player, I have learned to wear "different hats" when viewing the guitar technically. I don't claim that assertions in the realm of musicology have more or less intrinsic weight than technical assertions. It's just that they are only effective within their own area of application. As music is not really any kind of science, I am comfortable with subjective and casual evaluations. Where things go bad, is when they are awkwardly applied to a realm in which they don't function. A technical study of sound always risks falling to death in the chasm between the realms of music and science. Thus it deserves careful construction and support, as would a bridge (hope that doesn't abuse the metaphor . My statements may seem aggressive, since they exist in a public discourse in which there is usually no such caution. It is especially good that you are an active builder, with an interest in verification and a spirit of sharing information. It is too rare.
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Post by stratotarts on Nov 28, 2019 20:06:53 GMT -5
My point was partly that you might almost be capable of reaching full penetration. That would be welcome news to anyone who is DIY'ing as the vacuum apparatus is not exactly simple. Since you know the 50% @ 8 minutes data, you can extrapolate the capacitance to 100% fairly confidently. What is uncertain, is whether penetration occurs at a more or less fixed rate, thus leading to 100% penetration in about 15-20 minutes. A good point it seems to me. I suppose my motivation towards less than full waxing has been hearing from other winders more experienced than I that too much wax isn't necessarily a good thing. I do know that when I went to less wax I liked the sound of my PUP's better, but of course this introduces the whole microphonics issue, and coupled with wood species and design of the guitar it would seem hard to measure. My semi-hollow models sound quite different than solid bodies with the same PUP's and I'm guessing that microphonics play a part in that. Don't take this the wrong way, but from a scientific viewpoint, having knowledge of the internal characteristics instantly disqualifies you as an impartial judge of the sound. If you tooled those characteristics yourself, the chances of objectivity are even more reduced. This kind of bias has been shown not to be limited to only a few individuals, but is actually a normal human trait. In fact, the reason science demands so much rigour in eliminating bias, is because it is so built into us as human beings. Add to the mix, professional pride (no matter how well justified) and repetitive experiences which can reinforce things which are in fact imaginary, and what you have left are mere opinions. Some of these may turn out to be correct after rigorous testing. Many will not. In what is essentially a cottage industry consisting of craft more than science, such opinions have little value to contribute to the science other than providing starting points for investigation. There is no currency in the customer base of that industry to motivate expensive and time consuming scientific studies, so who can blame them? I think that when you consider the final actual degree of influence that wax plays on the sound, in light of the capacitance alone, you will find that the explanation is inadequate.
Some kind of responses to this are of the style, "if it isn't the capacitance, then what is it?", makes a huge assumption that there is any difference to begin with. It is like saying, "if UFOs don't exist, then how do you explain the abductions?". Well maybe there are none - just some imaginative, attention seeking and/or deluded people.
I can suggest two possible alternative explanations for such a real, perceptible difference. When a player holds a guitar, it is directly audible to the player acoustically due to the close proximity. An audience isn't as likely to hear it, they will get mostly the amplified sound because they are much further away. This is even more true if the guitar is not miked. I've heard that the "tone wood" debate can stir some resentment, so I won't go there at the moment. However, the same argument could be made for those differences. In any case, surely the composition and shape of the body has more effect on the acoustic (unamplified) output of the guitar than the pickup output, because it has been demonstrated that the pickup is a relatively insensitive acoustic microphone, compared with the level of the magnetic signal that is converted to the electrical output. The player is hearing both amplified and unamplified (in most genres anyway), and more so off stage.
If you are talking about hollow vs. solid body and potted vs. non-potted pickups you really have a 4 way comparison to do, and comparing only hollow body guitars with unpotted pickups vs. solid body with potted pickups won't generate any decisive conclusions. Self-anecdotal information is not without its value, but it doesn't map well to a larger world. That is the value of controlled experiments that carefully isolate one effect from all the others, and from the influence of human bias.
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