philbard
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Post by philbard on Nov 27, 2019 7:11:45 GMT -5
Hey Everyone, Longtime visitor, first post here. Hopefully the image attaches correctly... First of all thanks to Antigua for sharing his wealth of knowledge and technique for pickup testing. I've seen some discussion on the subject of wax potting of PUP's along with some audio based tests posted and it got me thinking that I'd like to see some simple comparisons of pot times that don't involve measurements that take the audio component out of the equation. So I performed some Bode Plots on a freshly wound bobbin with different pot times and am posting up the results. I invite your feedback on the results and welcome suggestions on my testing methods. I've been winding pickups for awhile now but have only recently begun making these types of plots. Here is how the tests were performed. I used a single Humbucker bobbin wound with 4638 turns of 42 gauge enamel wire. Parallel capacitance and DCR was measured with an ExTech LCR meter and the plots were made with a Velleman USB Oscilloscope. Used the oscilloscope's signal generator to send AC signals varying from 100 Hz up to 30KHz across the driver coil, a bobbin wound with 300 turns of 42 gauge wire, placed on top of the bobbin under test and measuring the resultant voltages generated therein, as described here. There were NO metal (slugs, baseplate, etc.) present and the circuit contained no load, so obviously peak frequencies are significantly higher than they would be for a fully assembled and installed Humbucker. As the Velleman's plot technology is rather primitive, I transferred the data to Excel. The plots attached show only the peak area of the data to improve visibility. All tests were made on the same bobbin, first with no wax, then with progressively longer times in the pot, which contained 100% paraffin, no beeswax. The first wax time was 45 seconds. After measurements the bobbin was returned to the pot and the timer started after about 15 seconds of immersion to allow the outer wax on the bobbin to soften and with confirmation that bubbles were rising, indicating wax penetration was resuming. All wax times reflect the cumulative totals. At about 10 minutes total time bubbles had stopped so I assumed the bobbin was pretty much fully saturated at that point. The plots show a progressive decrease in Resonant Peak frequency with increased pot time, starting at 19.7 KHz with no wax and finishing at 18.4 KHz with 10 min. Parallel Capacitance increased from 39 pFarads to 53 pFarads, measured at 100kHz as is commonly recommended. Output voltage was not affected nor was DCR throughout the tests. From this it would be logical to conclude that the amount of wax potting that a PUP undergoes does indeed have an affect on the audio signal that it produces, with more wax causing a shift to lower frequency (and likely warmer tonality). Note also that there is a broadening of the peak with longer times, which I assume would further warm tones, somewhat similar to what a tone control causes, as I've seen this in plots done on PUP's installed in guitars made at different tone settings. The rise in parallel capacitance would likely be the result the dielectric effect of the wax present between the turns of wire vs air in unwaxed coils. Hope this is of interest.. Cheers, Phil
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Post by newey on Nov 28, 2019 9:14:08 GMT -5
philbard-
Hello and Welcome to G-Nutz2!
Your image is fine, and this is an interesting analysis.
You mention using paraffin. I would expect the results to be identical regardless of potting material- beeswax, epoxy resin, whatever, so long as it permeates the coils completely, as your paraffin did after 10 minutes. Testing different materials would probably only serve to debunk internet anecdotes to the contrary.
But, around here, we like empirical data.
andrewbrown:
Also, Hello and Welcome to G-Nutz2!
You have simply quoted the previous posts, without asking a question or providing any further information, so it looked to me as if you might have mis-posted. That's OK, feel free to correct it as needed.
For the future, be aware that it is not necessary to quote entire previous posts- just drag to highlight the parts of a post that you wish to refer to, then hit the yellow "quote" button above. It is much more economical to do so, focusing on only the part of the previous post, rather than forcing subsequent readers to re-read the entire thing just to see what part you may be getting at.
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philbard
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Post by philbard on Nov 28, 2019 11:15:34 GMT -5
philbard- Hello and Welcome to G-Nutz2!Your image is fine, and this is an interesting analysis. You mention using paraffin. I would expect the results to be identical regardless of potting material- beeswax, epoxy resin, whatever, so long as it permeates the coils completely, as your paraffin did after 10 minutes. Testing different materials would probably only serve to debunk internet anecdotes to the contrary. But, around here, we like empirical data. I used paraffin only as that is the regime I've been using since starting to wind. Lindy Fralin has said he thinks beeswax dampens tone somewhat, and I went on his recommendation. Now, though, with the testing equipment and experience I have it would certainly be possible to do a test comparing wax formulations. Lots of work though, and it would have to be driven by a strong need to know this. At this point I'm only lightly waxing my PUP's, and am considering going with no wax based on this analysis. on another note, as I've been testing the whole PUP circuit with different guitar cables I'm more amazed at the difference cables make in tone. Aargh, so much reduction in resonant peaks! I'll post those results soon...
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Post by reTrEaD on Nov 28, 2019 13:19:15 GMT -5
I used paraffin only as that is the regime I've been using since starting to wind. Lindy Fralin has said he thinks beeswax dampens tone somewhat, and I went on his recommendation. Now, though, with the testing equipment and experience I have it would certainly be possible to do a test comparing wax formulations. Lots of work though, and it would have to be driven by a strong need to know this. At this point I'm only lightly waxing my PUP's, and am considering going with no wax based on this analysis. on another note, as I've been testing the whole PUP circuit with different guitar cables I'm more amazed at the difference cables make in tone. Aargh, so much reduction in resonant peaks! I'll post those results soon... Hi philbard First of all, your testing is much appreciated. But in my opinion, your discussion deserves its own thread. If you'd like to create a new thread on the Pickup Testing and Modeling board, you can do so and title it appropriately. No need to put much of anything in the Original Post of the new thread. A staff member can move your first post and the associated replies into your new thread. They'll fall in chronological order, so the first post you made here will become the Original Post of the new thread. If you have any questions about this process, you can PM me.
The dielectric constant of Beeswax and Paraffin wax are both higher than air. So expect both to result in a 'darkening' of tone. These waxes aren't just a singular molecular compound. They are mixtures of compounds and the amounts of each molecular compound in the mix can vary significantly. That's why most reference charts show a range, rather than a singular value for their constants. www.clippercontrols.com/pages/Dielectric-Constant-Values.htmlFrom the ranges listed there, I would expect Beeswax to have a greater effect on darkening of tone than Paraffin wax, since the listed range of dielectric constant is higher. As the wax displaces air between the windings, we can expect an increase in inter-winding capacitance because the dielectric constant is higher than air. Your results confirm this. It takes a significant amount of time for the wax to migrate to the inner windings. Shorter potting times only replace the air in the outer windings. I would also expect the thickness and dielectric constants of the various insulation materials used for the windings to have a much greater effect on inter-winding capacitance than potting.
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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 antigua on Nov 28, 2019 17:15:10 GMT -5
Hey Everyone, Longtime visitor, first post here. Hopefully the image attaches correctly... First of all thanks to Antigua for sharing his wealth of knowledge and technique for pickup testing. I've seen some discussion on the subject of wax potting of PUP's along with some audio based tests posted and it got me thinking that I'd like to see some simple comparisons of pot times that don't involve measurements that take the audio component out of the equation. So I performed some Bode Plots on a freshly wound bobbin with different pot times and am posting up the results. I invite your feedback on the results and welcome suggestions on my testing methods. I've been winding pickups for awhile now but have only recently begun making these types of plots. ... Thanks a lot for doing this. This is definately worthy of a thread of it's own, if you could make a new thread, that would be great, because I'd like to share this experimental research, and I would link people to the new thread. Your idea to use Excel for the plotting is really great. The main reason I've stuck with the Velleman's plotter is because I had dozens of pickups to test and I needed to save time, but for a one-off experiment I think this is a better way to go for sure. I bet Excel even supports performing calculations on the data for applying a -6dB per octave slope, if a person wanted or needed that form of plot. I think the 39pF to 53pF, +4pF change is the good info to take away from this. That's a 4,600 turn coil, so we might suppose that with an 8k turn coil the capacitance might increase by 7pF to 8pF. That degree of change would not be audible in situ, the loaded resonant peak would decrease by a very small amount, so I can't agree that wax potting actually does contribute to a warmer tone. The lower Q factor in situ means that a broader range of harmonics would increase or decrease, but by a very small amount, well below 1dB. I've noticed from testing tall versus wide coils that the overall capacitance has a lot more to do with the width of the coil than anything else. For example, a Strat pickup will have a capacitance of 90pF, a Jazzmaster pickup with the same DC resistance and wire gauge will be right about 45pF, 50% less capacitance for the fact that the coil is flat and wide, so I expected that any dielectric difference in either the wax or the insulation would cause a change that is much smaller than 50%, and sure enough it looks like it's closer to 20%. Regarding paraffin vs. beeswax, according to this physics.info/dielectrics/ and this www.clippercontrols.com/pages/Dielectric-Constant-Values.html the dielectric of beeswax is "2.7–3.0", where as the dielectric of paraffin is "2.1–2.5". It looks like the dielectric value of beeswax might be ~25% higher than paraffin, but an 8pF increase or decrease in capacitance wouldn't be audible, nor would a 10pF or 12pF difference. Because a typical guitar cable has a per-foot capacitance of around 40pF, wax potting be would comparable to making your guitar cable three inches longer or shorter, the difference between beeswax and paraffin... maybe one inch difference.
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philbard
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Post by philbard on Nov 28, 2019 17:55:45 GMT -5
Thanks a lot for doing this. This is definately worthy of a thread of it's own, if you could make a new thread, that would be great, because I'd like to share this experimental research, and I would link people to the new thread. Your idea to use Excel for the plotting is really great. The main reason I've stuck with the Velleman's plotter is because I had dozens of pickups to test and I needed to save time, but for a one-off experiment I think this is a better way to go for sure. I bet Excel even supports performing calculations on the data for applying a -6dB per octave slope, if a person wanted or needed that form of plot. I think the 39pF to 53pF, +4pF change is the good info to take away from this. That's a 4,600 turn coil, so we might suppose that with an 8k turn coil the capacitance might increase by 7pF to 8pF. That degree of change would not be audible in situ, the loaded resonant peak would decrease by a very small amount, so I can't agree that wax potting actually does contribute to a warmer tone. The lower Q factor in situ means that a broader range of harmonics would increase or decrease, but by a very small amount, well below 1dB. I've noticed from testing tall versus wide coils that the overall capacitance has a lot more to do with the width of the coil than anything else. For example, a Strat pickup will have a capacitance of 90pF, a Jazzmaster pickup with the same DC resistance and wire gauge will be right about 45pF, 50% less capacitance for the fact that the coil is flat and wide, so I expected that any dielectric difference in either the wax or the insulation would cause a change that is much smaller than 50%, and sure enough it looks like it's closer to 10%. Regarding paraffin vs. beeswax, according to this physics.info/dielectrics/ and this www.clippercontrols.com/pages/Dielectric-Constant-Values.html the dielectric of beeswax is "2.7–3.0", where as the dielectric of paraffin is "2.1–2.5 ". It looks like the dielectric value of beeswax might be ~25% higher than paraffin, but an 8pF increase or decrease in capacitance wouldn't be audible, nor would a 10pF or 12pF difference. Because a typical guitar cable has a per-foot capacitance of around 40pF, wax potting be would comparable to making your guitar cable three inches longer or shorter, the difference between beeswax and paraffin... maybe one inch difference. OK, starting up a new thread...
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philbard
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Post by philbard on Nov 28, 2019 18:02:04 GMT -5
Hello everyone, Posted this in another thread and at the moderator's request am starting a new one with the original post... First of all thanks to Antigua for sharing his wealth of knowledge and technique for pickup testing. I've seen some discussion on the subject of wax potting of PUP's along with some audio based tests posted and it got me thinking that I'd like to see some simple comparisons of pot times that don't involve measurements that take the audio component out of the equation. So I performed some Bode Plots on a freshly wound bobbin with different pot times and am posting up the results. I invite your feedback on the results and welcome suggestions on my testing methods. I've been winding pickups for awhile now but have only recently begun making these types of plots. Here is how the tests were performed. I used a single Humbucker bobbin wound with 4638 turns of 42 gauge enamel wire. Parallel capacitance and DCR was measured with an ExTech LCR meter and the plots were made with a Velleman USB Oscilloscope. Used the oscilloscope's signal generator to send AC signals varying from 100 Hz up to 30KHz across the driver coil, a bobbin wound with 300 turns of 42 gauge wire, placed on top of the bobbin under test and measuring the resultant voltages generated therein, as described here. There were NO metal (slugs, baseplate, etc.) present and the circuit contained no load, so obviously peak frequencies are significantly higher than they would be for a fully assembled and installed Humbucker. As the Velleman's plot technology is rather primitive, I transferred the data to Excel. The plots attached show only the peak area of the data to improve visibility. All tests were made on the same bobbin, first with no wax, then with progressively longer times in the pot, which contained 100% paraffin, no beeswax. The first wax time was 45 seconds. After measurements the bobbin was returned to the pot and the timer started after about 15 seconds of immersion to allow the outer wax on the bobbin to soften and with confirmation that bubbles were rising, indicating wax penetration was resuming. All wax times reflect the cumulative totals. At about 10 minutes total time bubbles had stopped so I assumed the bobbin was pretty much fully saturated at that point. The plots show a progressive decrease in Resonant Peak frequency with increased pot time, starting at 19.7 KHz with no wax and finishing at 18.4 KHz with 10 min. Parallel Capacitance increased from 39 pFarads to 53 pFarads, measured at 100kHz as is commonly recommended. Output voltage was not affected nor was DCR throughout the tests. From this it would be logical to conclude that the amount of wax potting that a PUP undergoes does indeed have an affect on the audio signal that it produces, with more wax causing a shift to lower frequency (and likely warmer tonality). Note also that there is a broadening of the peak with longer times, which I assume would further warm tones, somewhat similar to what a tone control causes, as I've seen this in plots done on PUP's installed in guitars made at different tone settings. The rise in parallel capacitance would likely be the result the dielectric effect of the wax present between the turns of wire vs air in unwaxed coils. Hope this is of interest.. Cheers, Phil
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philbard
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Post by philbard on Nov 28, 2019 18:08:04 GMT -5
I think the 39pF to 53pF, +4pF change is the good info to take away from this. That's a 4,600 turn coil, so we might suppose that with an 8k turn coil the capacitance might increase by 7pF to 8pF. That degree of change would not be audible in situ, the loaded resonant peak would decrease by a very small amount, so I can't agree that wax potting actually does contribute to a warmer tone. The lower Q factor in situ means that a broader range of harmonics would increase or decrease, but by a very small amount, well below 1dB. OK, starting up a new thread... Actually, the overall change was 14pF, leading to 28pF in your assumption of the increase with 2 coils. Not a lot but not insignificant.
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Post by antigua on Nov 28, 2019 18:21:57 GMT -5
OK, starting up a new thread... Actually, the overall change was 14pF, leading to 28pF in your assumption of the increase with 2 coils. Not a lot but not insignificant. You're right I did the math wrong, but if you have two coils in series, the capacitance cuts in half rather than add together. If the coils are wired in parallel, the capacitance would sum together. That makes me wonder what would happen if you doubled the number of turns with just one coil, it might end up splitting the difference. I would say that even 28pF is inaudible though, going back to the guitar cable analogy, that's not even a foot's worth of difference. I make cap selectors for a lot of my guitars, I've tried different caps as low as 47pF, but I can't hear any change in the sound until the step is closer to 1nF. With guitar products, sometimes its more the thought that counts, though.
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philbard
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Post by philbard on Nov 28, 2019 18:28:48 GMT -5
Actually, the overall change was 14pF, leading to 28pF in your assumption of the increase with 2 coils. Not a lot but not insignificant. You're right I did the math wrong, but if you have two coils in series, the capacitance cuts in half rather than add together. If the coils are wired in parallel, the capacitance would sum together. That makes me wonder what would happen if you doubled the number of turns with just one coil, it might end up splitting the difference. Oh yes, of course that's true. My mistake about the 2 coils
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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 antigua on Nov 28, 2019 18:39:49 GMT -5
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Post by antigua on Nov 28, 2019 18:41:10 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? That's a good point, maybe Phil can cut into the coil and see how deep the wax went.
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philbard
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Post by philbard on Nov 28, 2019 18:43:19 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? 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.
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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 antigua on Nov 28, 2019 18:54:50 GMT -5
Thanks a lot for doing this test. The fact that you found a difference at all has inspired me to get on this and do tests of my own. I have both paraffin and beeswax, I'll get on this.
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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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philbard
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Post by philbard on Nov 28, 2019 19:14:38 GMT -5
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. 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.
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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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philbard
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Post by philbard on Nov 28, 2019 21:27:38 GMT -5
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.
Ouch, seems a bit coldly scientific. I get your point about bias, and also about unamplified sound, but I disagree that having knowledge of the design automatically disqualifies one from being objective. It may of course influence an opinion, probably varies person to person. As I've built guitars over the years I've grown much more sensitive to their varying characteristics and out of a desire to build them better go out of my way to try to avoid preconceived notions or bias. That involves listening over and over, and also putting them in front of knowledgeable players and allowing them to give feedback as opposed to soliciting it. I listen to others as much as I do to the guitars. You are making some pretty large assumptions here, and all due respect I don't want to enter into a back and forth about it. I agree with you that scientific testing is not opinionated and can provide great clarity, that's why I did this experiment in the first place. Admittedly I'm not far enough along in pickup analysis to generate much in the way of conclusions, but that's also why I posted up.
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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 antigua on Nov 29, 2019 2:50:48 GMT -5
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. I have a thread here guitarnuts2.proboards.com/thread/8521/testing-microphonics-potted-paf-clone with some testing related to microphonics and unpotted pickups. I couldn't find evidence of potential for audible microphonics. The induced voltages were very close to the noise floor. It was orders of magnitude below the normal output voltage, even when the pickup was situated such that it vibrated a lot more powerfully (attached to the head stock) than it would when fixed under the strings. It's relatively easy to test first hand, just secure an unpotted pickup to the head stock (which produces a stronger vibration than any other location on the guitar), connect the pickup to a guitar amp, and see how much signal you get from the pickup in it's capacity as a microphone. Then plug the guitar in properly, through the input jack, and note the difference in amplitude between the head stock pickup, and the properly installed pickups. I agree that solid, semi hallow and hallow bodies sound different. I have a solid and mostly hallow Les Paul, they have a different sound, IMO. The thing is, they all have wax potted pickups, and they sound different nevertheless. For that and the reasons above, I'm inclined look at other causes for the solid and semi hallow guitars to sound different. IMO, what is probably happening, is that the hallowed out parts of the body cause the structure to be less rigid along the end-to-end axis, the body contorts more and is acoustically louder for that reason, and the reduced rigidity causes the higher harmonics to decay more rapidly, leaving the mids and lows to linger longer, making for an overall "warmer" sound. I'm trying to think of a good way to test microphonics based on light versus extensive wax potting, but inducing a constant vibration can be tricky, a slight mistake can vary the input, which in turn varies the output, which can then be misinterpreted as a meaningful difference. It seems to me though, logically, if the inner windings are sealed off from the outside air, they're not going to move in response to sound waves, for the same reason that BB King had the f-hole wings of his ES-335 sealed shut, once the chambers are air tight, they cease to be as microphonic. One might suppose that the existence of vacuum wax potting implies that it's extra beneficial, but if there's one thing I've learned in the world of guitar, people get the idea that doing things a certain way must be better, then that becomes the way things are done, and the original rational gets lost in time. Case in point, the various theories about what purpose the base plate of a Tele bridge pickup serves, or the reason why PAF pickups have six screws and six slugs.
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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 antigua on Nov 29, 2019 11:38:59 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. He mentioned 100khz in the OP. Interesting observation, could it be reasoned that the ratio of increase in capacitance implies the thoroughness of the wax penetration? A coil I wound for testing had no wax potting, it measured 84pF, and I have measured wax potted pickups with nearly that low of a capacitance also, but I've also had many Strat pickups measure as high as 150pF, and beyond. There are a few reasons why they could potentially vary so greatly, such as insulation and coil tension, but this experiment goes to show that maybe much of the difference is wax potting, and how deeply the wax penetrates.
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Post by antigua on Nov 29, 2019 17:58:23 GMT -5
I'm conducting an experiment now with beeswax. I'll post all the details in a new thread, because I have lots of pictures and plots, but one thing I want to reveal sooner than later is that the capacitance increased remarkably. Strat pickup with 2.5H inductance, about 102pF capacitance prior to wax potting, jumped up to 147pF after 10 minutes of submersion in beeswax at 205 degrees Fahrenheit.
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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 antigua on Nov 29, 2019 19:08:50 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. That's a good point. My test pickup went from about 100pF to 150pF in the first ten minutes, and even after a full hour in the wax it's still around 150pF. I think it's fully saturated, despite there not being any vacuum. It's impossible to know what the capacitance would have been if there was no insulation on the wire. The interesting thing about this is 100pF to 150pF is almost exactly the sort of spread I've measured among dozens of Strat pickups. The degree of wax potting might be the underlying cause for the spread.
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philbard
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Post by philbard on Nov 29, 2019 19:15:59 GMT -5
I agree that solid, semi hallow and hallow bodies sound different. I have a solid and mostly hallow Les Paul, they have a different sound, IMO. The thing is, they all have wax potted pickups, and they sound different nevertheless. For that and the reasons above, I'm inclined look at other causes for the solid and semi hallow guitars to sound different. IMO, what is probably happening, is that the hallowed out parts of the body cause the structure to be less rigid along the end-to-end axis, the body contorts more and is acoustically louder for that reason, and the reduced rigidity causes the higher harmonics to decay more rapidly, leaving the mids and lows to linger longer, making for an overall "warmer" sound. Obviously there is something going on so that the construction of the guitar affects the sound, otherwise every pickup would sound exactly the same no matter where it was installed, and I think we could agree that they do not.
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philbard
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Post by philbard on Nov 29, 2019 19:25:20 GMT -5
That's a good point. My test pickup went from about 100pF to 150pF in the first ten minutes, and even after a full hour in the wax it's still around 150pF. I think it's fully saturated, despite there not being any vacuum. It's impossible to know what the capacitance would have been if there was no insulation on the wire. The interesting thing about this is 100pF to 150pF is almost exactly the sort of spread I've measured among dozens of Strat pickups. The degree of wax potting might be the underlying cause for the spread. Its not an apples to apples comparison, but my Humbuckers waxed at 2 min almost always come in around 85-90pf. This compares to 120pf with several I have from Seymour and Lollar at similar DCR that they described as waxed, how much of course they do not say as far as I've seen. I use the same 42 gauge enamel wire, from the same supplier that Seymour buys from. I'd have to do more testing to find out what the capacitance would be if they were unpotted or fully potted, but I'll wind a second coil with same wax time and assemble it with the first to see where capacitance goes. Might provide a data point...
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