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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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Post by stratotarts on Nov 28, 2019 18:55:32 GMT -5
That's a good point, maybe Phil can cut into the coil and see how deep the wax went. I'm planning to keep this coil, make a mate to it and assemble for plots with all the hardware present to see how much reduction to the peaks occurs after all the metal is introduced when compared to unwaxed PUP's. But in the past I've cut through some coils that were waxed for 8 minutes and my recollection was that penetration was about halfway or so. 2 minute wax potting produced about 20-25% penetration, but bear in mind this was NOT a quantitative measurement. Also, I'm not using vacuum potting as I'm really not trying for full penetration at this point. 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.
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Post by stratotarts on Nov 28, 2019 18:49:51 GMT -5
My understanding from some previous online research regarding the original reasons for using beeswax vs. paraffin is that beeswax has a higher melting point (thus resisting melting in-situ) and is also less brittle (hence maybe less likely to break wires as it expands/contracts with temperature). I think the tone difference thing is just a "back-splanation".
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Post by stratotarts on Nov 28, 2019 18:37:02 GMT -5
May I assume this is non-vacuum wax potting? As well as providing some useful hard data on the effect of potting, this experiment also shows that wax penetration might be achieved without vacuum - at the cost of longer potting time. However, it is not certain that the 10 minute immersion leads to 100% coil penetration - just the maximum achievable with this method. I wonder - how would the 10 min potting compare with a full vacuum potting?
An interesting follow up to this experiment, would be to measure the microphonic potential for each degree of immersion...
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Post by stratotarts on Nov 28, 2019 17:11:46 GMT -5
A reminder - when you are evaluating the audible effects of varying some physical parameter, it is important to acknowledge that response almost always varies substantially less in a loaded configuration than in an unloaded one (such as unloaded resonant frequency). It's not that there isn't a difference - it is just important to put it in the perspective of a working circuit.
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Post by stratotarts on Nov 20, 2019 9:33:25 GMT -5
What I'd like to study now are the following: 1. How much change in Volume Pot resistance is needed to hear any difference in sound/tone? i.e. If I have 2 pots rated at 250k, having the actual values of is 247k and 251k, will the sound differ? (assuming volume pot is at 10). Or do I need a drastic change, say from 250k to 300k, or 250k to 500k in order to hear any difference? 2. Similar with the pots question. How much change in Tone capacitor capacitance is needed to hear any difference in sound/tone? i.e. If I have 2 caps rated at 0.047uF, having the actual values of is 0.045uF and 0.049uF, will the sound differ? (assuming tone pot is at 10). If not, will changing the value to 0.033uF or 0.022uF give audible result? Or is the effect more felt when the tone pot is being rolled down? 3. I'd like to understand how different capacitor types (mylar, ceramic, orange drop and paper-in-oil caps) affect the overall sound. If I have different types of capacitor having the same values. Will they sound any different, and why? Is the difference because of tiny difference in actual capacitance values or is it because of different dielectric materials? Thank you! What you are asking, can not be definitively answered in purely technical terms, because it is a perceptual question, "what does it sound like?". A definitive technical answer can only be obtained with listening tests, properly implemented in such a way as to eliminate cognitive biases. You can form an opinion, based on applying the results of other listening tests to the subject phenomena. Such an opinion will often be right, but not always. Such an opinion will always be provisional and has to compete with other, often lesser informed, opinions because it has no direct experimental basis. This is why you will see 1000 different online opinions on your question #3, for example.
Generally, facts are regarded highly here, and the only way to establish your questions factually and definitively, is to perform the listening tests scientifically.
Having said that, the answers are:
1. Enough difference to create at least a 1dB difference in the loaded resonant peak 2. Almost the same as #1, except that it is a frequency shift rather than amplitude. Also the difference diminishes rapidly as you turn up the tone control. 3. Different cap types have no audible influence on the sound. It's because their characteristics don't vary enough for that.
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Post by stratotarts on Oct 11, 2019 8:15:46 GMT -5
Cool!
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Post by stratotarts on Sept 10, 2019 7:04:16 GMT -5
I think any exciter coil results will be useful only with that particular setup - change the exciter coil and you can't compare to previous results w/o careful calibration. This is an example of the usefulness of keeping a reference pickup. I have one "golden unit" that I use for things like that.
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Post by stratotarts on Sept 6, 2019 21:24:14 GMT -5
If all of the pickups are of the same design (i.e. Strat, HB, P90, etc) I would be surprised if, at the end of the day, an exciter coil with a fixed spacer to enforce a standard exciter to pickup distance and a simple multiplication by the measured Gauss at the pole tops did not come exceedingly close to the result you're looking for. A software scope will produce the same results for a given input consistently.
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Post by stratotarts on Sept 4, 2019 21:44:30 GMT -5
Well, there is this method:
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Post by stratotarts on Aug 10, 2019 7:58:21 GMT -5
The impedance curve is measured with different capacitive loads and the parameters are deduced from fitting L C R and K to the results.
Arthur
Why? You have a means of measuring the complex impedance as a function of frequency directly. The effective L as a function of f, etc. follow directly from that. The device is a black box. How can you know what portion of the complex impedance is due to capacitive reactance and what portion due to inductive reactance, at any given frequency? Is there not more than one pair of LC value that will produce the same phase angle, same complex impedance?
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Post by stratotarts on Aug 8, 2019 18:22:00 GMT -5
Thank you, Antigua! Learned a lot from this! Regarding coil winding... What if I have a 42AWG and wound 8000 turns which resulted to 6k ohms of DCR and an inductance of 2.5H, what are the things that I can do to get a higher/lower values for inductance (given the same 42AWG wire with 8000 turns)? I believe that the DCR won’t be affected since I still have the same wire length (8000 turns of 42AWG). I’m guessing that the way I wound (scatter or not, tight or loose) will have an effect on the inductance? Is this correct or not? If yes, how much change in inductance can I expect? Thank you! Given a fixed turns count, the diameter of the coil is about the only way in which the winding style can influence inductance. A tight coil will be marginally smaller, and therefore have a slightly lower inductance. But the difference is probably not even measureable. Also given a fixed mechanical design, using the same materials in every case, the wind count is actually the main influence on the inductance value. In fact, the wire diameter doesn't even have much influence there. 8000 turns of #42 will be very close to 8000 turns of #43. That small difference exists for the same reason - the coil diameter will be different.
You can see this going on with some Strat sets - they all measure almost identical inductance! Why? Because they are machine wound and the machine puts a precise number of turns on the coil. It's the easiest production method for controlling the coil specs. In this pickup set you can see it with the middle and neck pickup measurements. The bridge is intentionally made different with a higher wind count.
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Post by stratotarts on Aug 3, 2019 9:47:39 GMT -5
M is a measure of the voltage induced in one coil by current flowing in the other as a result of the coils sharing a magnetic flux. So if I apply one volt to the primary coil with a function generator, all I have to do is measure the voltage across the secondary to get M? Can the coupling coefficient be derived from that? Not directly, because the output is load dependent. With a fixed resistive load, there might be a formula for it. I don't know what it would be.
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Post by stratotarts on Jul 9, 2019 8:18:39 GMT -5
There's no doubt that you can get relatively high Q with some really thick steel blades - I measured a loaded peak of 2.0dB on import mini HB's with the cover removed:
Yes, the coupling counts but I think there is something about the geometry that also provides some mediation.
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Post by stratotarts on Jul 8, 2019 12:54:20 GMT -5
I think one has to look at a greater sampling of pickups to answer that - I checked my database and found some surprising variation in the Q among different humbuckers. For example, if you are comparing blades to PAF types, I measured a loaded peak of 1.4dB on the SD Seth Lover. That is a covered pickup, so it would be more without the cover. The SH-1N '59 which is an open model, was 2.4dB. It seems to me that the comparison units that were represented here, have a below average Q. I do wonder if the blades are perhaps nickel instead of steel?
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Post by stratotarts on Jul 2, 2019 7:03:26 GMT -5
3) I have tried it with and without the series resistance and I tend to get the same results either way (same Q factor, same resonant peak frequency), but Ken Willmott is an electrical engineer by trade, so I'd do it if he suggests it. You might try for yourself, with and without, and report if happen to find a difference. With an audio card, I recommend driving the test coil with a headphone output, which usually has a fairly high output impedance (example 100-300 ohms). The software oscilloscope built in signal generator usually has an output impedance of 50 ohms. So when the coil is directly connected, there is already an effective series resistance, just not as great as the combined series resistance of that and the 100 ohm resistor. The difference will only show up at a very high frequency, where the coil's inductive reactance becomes equal to, or greater than, the source resistance. The purpose of the 100 ohm resistor is to guarantee proper operation regardless of what kind of signal voltage source is used.
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Post by stratotarts on Jun 7, 2019 15:39:37 GMT -5
My main question is this: A Single Coil with 2,3 H would be in the lower range, so why is the Hummie with same Inductance fatter and "woolier" than a Strat SC ? The most likely difference is the steel poles vs. Alnico poles. The amplitude of the resonant peak is much less with the steel poles (whether slugs or screws). Many people find the ceramic single coils "fatter" or "duller" than the Alnico's for the same reason. That happens because of eddy current losses in the steel parts. Another factor is the well known "aperture effect" that mitigates upper harmonics. <iframe style="position: absolute; width: 34.180000000000064px; height: 3.240000000000009px; z-index: -9999; border-style: none;left: 15px; top: -5px;" id="MoatPxIOPT2_97047727" scrolling="no" width="34.180000000000064" height="3.240000000000009"></iframe> <iframe style="position: absolute; width: 34.18px; height: 3.24px; z-index: -9999; border-style: none; left: 1638px; top: -5px;" id="MoatPxIOPT2_88314869" scrolling="no" width="34.180000000000064" height="3.240000000000009"></iframe> <iframe style="position: absolute; width: 34.18px; height: 3.24px; z-index: -9999; border-style: none; left: 15px; top: 102px;" id="MoatPxIOPT2_43862792" scrolling="no" width="34.180000000000064" height="3.240000000000009"></iframe> <iframe style="position: absolute; width: 34.18px; height: 3.24px; z-index: -9999; border-style: none; left: 1638px; top: 102px;" id="MoatPxIOPT2_32383119" scrolling="no" width="34.180000000000064" height="3.240000000000009"></iframe>
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Post by stratotarts on May 22, 2019 10:00:52 GMT -5
Skin effect is not dependent on current density - only on frequency. A Faraday cage surrounding a circuit (so, a shielded guitar wiring cavity) provides both electrostatic and electromagnetic shielding. It does not provide any magnetic shielding. Electrostatic shielding does not require very low wall resistance because of the high ratio between that resistance and the extremely high source impedances involved. I think the explanation why shields with relatively high resistance (such as conductive paint) have been found acceptable, is for that reason, and also that the environmental levels of electrostatic noise are much higher than those of electromagnetic noise. Additionally, the amplifier input is usually specifically engineered to reject frequencies above audio. Also, like all waves, EM wave length increases as the frequency decreases, and objects that are much smaller than half a wavelength are not able to function as an efficient receiving antenna. Even at 100MHz, the wavelength is longer than a guitar. Cellular signals are much shorter, which contributes to some guitar circuit sensitivity to proximate cellphones (especially GSM/TDMA protocols that transmit in "bursts").
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Post by stratotarts on May 1, 2019 18:35:56 GMT -5
Does this mean that the string field appears to the pickup poles and coil, mainly as a magnetic dipole in the same axis? In other words, could it be modeled approximately as a solenoid coil positioned axially, exactly as an exciter coil is usually placed?
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Post by stratotarts on Apr 19, 2019 9:41:37 GMT -5
The accuracy and resolution of FEMM type analysis plots is not high enough to isolate the field due to the string directly.
I tried enabling B vector labeling on the plots, selecting a scale factor of 100. That seems to magnify the field enough to see what's going on, unless I'm missing something? I modeled the string as two tiny Neo's back to back in line with a steel string, 2mm from a steel pole. The idea is to show the increase in string field intensity in the coil region due to the steel pole.
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Post by stratotarts on Apr 17, 2019 12:46:56 GMT -5
How did the inductance reduction due to coupled opposing coil polarities work out? Do you have bode plots or specs?
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Post by stratotarts on Apr 11, 2019 19:27:22 GMT -5
Very cool construction. Thanks for sharing.
Your Neo magnets are next to the string, right? I ask because my Neo humbucker conversion did, and it has a whopping string pull even though I lowered them about 2mm from the top bobbin face with wooden plugs over them. Those were humbucker pole diameter sized Neo's (yes I lucked out finding them). Did the magnet you use have a low enough force that the string pull is normal? What kind of field strength are you seeing at the string location?
It reminds me also that some of the Neo's I've seen have magnets attached to the bottom of the poles rather than the top. What sort of differences are there, such as dependence on permeability? Or other things? I have tried attaching Neo's to the end of some poles. I found that the pole material saturates at some maximum, much less than the Neo, in the case of steel and ferrite.
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Post by stratotarts on Mar 15, 2019 10:30:49 GMT -5
That is a one piece molded plastic bobbin. I wind my coils on the same type, which I bought brand new in bulk online from China. I think I'm only using 50 turns of wire instead of 200, but the exact number of turns does not make much of a difference.
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Post by stratotarts on Mar 11, 2019 18:06:13 GMT -5
Awesome! I'll have to set aside some reading time!
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Post by stratotarts on Feb 7, 2019 8:00:32 GMT -5
I'm not saying that it is definitely the cause, but I have noticed that 50/60 Hz noise can sometimes produce uneven response below 100Hz. I've also seen irregular responses above 100Hz when the test loop headroom is exceeded and distortion starts to creep in. It's essential to have adequate S/N across the entire test frequency range.
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Post by stratotarts on Jan 22, 2019 13:52:52 GMT -5
It might have been overwound "hot" to compensate for the inherent losses of a sidewinder. That would boost the capacitance, I think. Keep in mind, the inductance of the two series coils is reduced substantially by the mutual coupling of the two coils, since they are collinear and opposite in phase. This effect was confirmed by my experiments with home brew sidewinders, although I can't report much detail because it was some time ago. The overall device inductance affects what you think the capacitance "should be". Interesting about the mutual coupling. I have not been thinking about that, a mistake, but I will. But first, I am wondering about the inherent losses of sidewinders; what are they? I am thinking, at least at the moment, that the negative mutual coupling is a good thing because it lowers the inductance (and thus raises the resonant frequency as resulting from external capacitance) without affecting the output level (at frequencies well bellow the resonance). Well, I have an opinion about the losses, but since the emphasis here is on demonstrable facts, I'll hold on to most of it for now, because I have to admit that I have not been able to verify it yet. But I think it's because the string field density is lower on the lower half of each coil (furthest away from the string). I had a long email discussion with Tucson about the general idea of measuring coil sensitivity (rather than about sidewinders), and he steered me towards a view that only considers the total flux density inside the coil loop, discounting the validity of considering parts of the loop separately. However, I think everyone could still accept that the off axis flux density of the string field is less than the on axis density. In other words, I think both "views" produce the same results in practice. Check it out and then use whatever explanation makes you happy, is my attitude. I haven't had time lately for in depth research.
Yes, the reduction in inductance is a surprise bonus, increasing the frequency response with apparently no penalties. Another interesting question is, whether poles are really necessary inside the coils. The prototypes I built didn't have any. So little time.
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Post by stratotarts on Jan 22, 2019 11:57:57 GMT -5
It might have been overwound "hot" to compensate for the inherent losses of a sidewinder. That would boost the capacitance, I think. Keep in mind, the inductance of the two series coils is reduced substantially by the mutual coupling of the two coils, since they are collinear and opposite in phase. This effect was confirmed by my experiments with home brew sidewinders, although I can't report much detail because it was some time ago. The overall device inductance affects what you think the capacitance "should be".
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Post by stratotarts on Jan 3, 2019 8:38:31 GMT -5
I proposed an untested mod to eliminate that eddy loss. I'm sure it will work. But it doesn't make practical sense, because the effect is so small:
I suppose you could at least say that a non-wraparound bridge like a Strat hardtail doesn't have this effect.
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Post by stratotarts on Dec 23, 2018 20:26:04 GMT -5
Brilliant! I get it. Thanks, I will try it out.
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