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Post by stratotarts on Aug 21, 2022 20:14:30 GMT -5
Yes, they aren't exactly the same "animal", the Wizard and the Integrator. I plan to build one so I have both. Member "ms" did some similar work with a simple resistor network circuit and posted it here quite a while ago. I haven't made any final decisions about it. I have become short of time lately, and the redesign is a major one, although the circuit itself won't change very much. So it seems daunting, but as the year goes on I might feel more optimistic about it. Could also just be some post Covid blues...
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Post by stratotarts on Aug 21, 2022 16:26:30 GMT -5
I downloaded it and had a read of the manual. I haven't tried it out yet. The main thing I'm wondering, is it an "integrator killer"? I was getting ready to do a major design re-make of the 5.9 integrator. This worries me. I don't have any serious "irons in the fire" apart from that, but it seems pointless to invest major time and money into a redesign if a device like this becomes the instrument of choice for measurements. So I'm thinking, if it really works, I might have to walk away from supplying integrators entirely. The whole point of the redesign was to reduce the assembly labour, which I now see was grossly under profitable. But if the demand is going to fall off, I can't really assume that risk. I guess it was just a matter of time.
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Post by stratotarts on Jul 9, 2022 20:37:49 GMT -5
It's easy to determine. Just run back to back plots, one with and one without a string. You can simulate the worst case by laying the string directly between the test coil and the pickup. Please try it and report.
I could do that test, but how would that change the plot? The coils would still be getting the signal from the drive coil, the string wouldn't be moving. I got caught with a misunderstanding of your acquaintance's comment. Such comments have to be fully fleshed out in order to really address any issues that they raise. I assumed by "the difference in magnetism", it was meant, the effect of the presence of the string on the static field produced by the magnet. In fact, the description is pretty open ended and doesn't specify what differences should be taken into consideration.
It is well understood and proven that a stronger magnet produces a stronger magnetic field in the string. This in turn, produces an increase in output for a given string excursion, as a simple result of Faraday's law. But the fundamental information in a Bode plot is not the absolute amplitude, but the relative amplitudes at different frequencies. A Bode plot can display different output amplitudes, as you can see from your experimental plot (evidenced in the flat line portion of lower frequencies).
There are only two accepted additional factors that differ from the application of test coil (there are probably more I can't think of right now, but I believe these are the most significant) - magnetic string pull, and non-linearity due to distance. But can you see, those are almost equal in different pickups of the same general type and physical position in the guitar. They are also not fixed but vary according to pickup height adjustment. Experiments that cover both of those are hosted somewhere on this sub-forum but it's become quite long and hard to find stuff (which isn't completely bad).
It's true that to consider, say, the sonic difference between an A2 and an A5, it would be perfect to somehow measure the two previously mentioned effects, in addition to the Bode plot. This would give you a more complete picture. But before it should be taken as a serious flaw in testing, it should be adequately demonstrated (and it is really in the court of this well-known figure to do so instead of postulating) that those effects are significant compared with other effects.
The main value of this forum, is that rather than being a melting pot for theories, postulates, and rhetorical discussions, it has focused on the design and implementation of actual and reliable tests. These can then be incorporated into a larger theoretical understanding of the devices, which does involve some synthetic thinking and discussion. It's always been a problem (in my view) that public discussions in some other forums, are mostly verbal generalities and theories that depend on plausibility to gain acceptance. Most of the actual progress in understanding pickup physics has been achieved not through the development or promotion of theories alone, but on carefully designed and performed experiments.
You said, "I want my charts to accurately reflect a pickup's character". You should think of character as a multifaceted result of many factors, which differ greatly in their significance. You will never find a single factor that 100% determines the sound. But the Bode plot response encapsulates a few of the most important factors. The main advantage of the plot is that it reveals inductance and Q in a way that has an almost one-one correspondence with the way it will respond in the guitar circuit. Breaking that down, inductance and Q (the most influential factors) can be measured and assigned values recorded with a DCR meter. But the results can't be seen in such a graphic way. Also those parameters vary with frequency and so a single inductance or Q measurement will never represent a complete measurement such as you have with a Bode plot.
An analysis of "character" also has to consider the perceptual side of things, how changes in the actual response change the perceived sound. Looking at things from this end, and attempting to connect with the features of a Bode plot, it becomes obvious with some testing and comparison (and consideration of general opinions about different pickup types), that there are three main aspects that do correspond directly with the plot - low pass response (-3dB cut off frequency)
- Q
- output amplitude
All of those are directly or indirectly seen in the plot. I've seen some attempts to 2-d map pickup types by the first two factors above, that produce "tone zones", for example - low cutoff, low Q = humbucker
- high cutoff, high Q = Strat
- medium cutoff, high Q = Tele
and so on, if you map individual pickup measurements to this map, you will definitely see them cluster and recognize the patterns that develop. But because the perceptual axes for those can only be two, they can't rationally express characteristics that are not expressed in such a map. Many such characteristics are controversial for the reason that they can't be measured in this way, but it doesn't paint the Bode plot as unreliable, only incomplete. So you can say, "a chart can not fully reflect a pickup's character". But a Bode plot never does, or at least never should stand in isolation. Knowing the type of pickup, therefore knowing more about its other physical characteristics as a group, adds meaning to the plot because you can confidently compare members of the same group.
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Post by stratotarts on Jul 8, 2022 10:03:11 GMT -5
It's easy to determine. Just run back to back plots, one with and one without a string. You can simulate the worst case by laying the string directly between the test coil and the pickup. Please try it and report.
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Post by stratotarts on Jul 6, 2022 9:30:20 GMT -5
First, 9V DC on the input test leads of the V5.9 integrator will not damage it. So don't worry about that.
I can't imagine, though, why there would be 9V in any measurement configuration. If the black shielded wire is the pickup output, as it appears to be, then the integrator leads should be connected:
ground (black/brown) -> black cable shield input (red) -> black cable inner white wire
You have to power the pickup normally, as it is an active pickup.
I am assuming you wish to make a normal output measurement, not something like a direct reading of one of the internal coils.
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Post by stratotarts on Jun 22, 2022 12:09:31 GMT -5
Compression in the amplifier front end is the basis of "dynamics". Not in the pickup.
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Post by stratotarts on Jun 22, 2022 11:58:28 GMT -5
Isn't this just a case of, DiMarzio specs being wrong?
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Post by stratotarts on Apr 23, 2022 19:37:40 GMT -5
I did try thinning a cover. It was a few years ago, so I don't have details. All I remember is that I ground as much off as I dared, without damaging the cover. It made no measurable difference (it was not possible to be perfectly exact, because the cover had to be removed/replaced in between tests). My conclusion, considering results of other tests involving the effects of copper foil, that the material can not be so thick as to be substantially rigid, or else it will incur significant losses. Because ohmic losses are proportional to the area of the cross section of the conductor, it comes as no surprise.
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Post by stratotarts on Apr 7, 2022 16:04:48 GMT -5
Oh, you're using it to monitor the source on channel B. That is okay, but I think it wouldn't be necessary because the software generates the signal generator output itself, therefore already knows the timing, and can calculate the channel A input phase difference from that.
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Post by stratotarts on Apr 4, 2022 13:50:22 GMT -5
A statistical breakdown on unloaded pickups won't produce much useful insight. The inductance, yes, but the capacitance doesn't contribute enough difference to the final loaded response to be relevant in a bulk comparison.
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Post by stratotarts on Apr 4, 2022 13:31:36 GMT -5
Also, the bare unloaded Q of the pickup is never heard in practice, when you listen, you are hearing it in the guitar circuit which loads it. The resistive load of the controls has approximately 10 times the influence on the Q, as does the wire resistance. Potentiometers are usually specificied with very wide tolerances compared with most fixed resistors, so it doesn't make sense to agonize over a small difference in the coil resistance, even if you are worried about Q generally.
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Post by stratotarts on Apr 4, 2022 8:45:36 GMT -5
Bode plots are made with a Velleman PCSGU250 and the supplied probes in 10x mode, with the function generator feeding a driver coil of 0.48mH, placed on top of the pickup and driven with 2Vpp. The pickup is connected to an integrator circuit, designed by Ken Willmott kenwillmott.com/blog/, with a Velleman 10x probe, and fed back into the Velleman PCSGU250. I measured the probes' capacitance at 20pF, so that amount is subtracted from the capacitance calculation. Sorry, I've been preoccupied with things other than pickup testing for a while, so I may have missed some things. When did scope probes enter the picture? For what purpose? Where are they connected? Every configuration that I can think of, using a 10x probe, has problems or else is not helpful.
If the probe is in line before the integrator, it adds 20dB of loss, and is not terminated in the correct impedance, 1.0M. Also, as you have discovered already, the capacitance of the probe is actually greater than that of the integrator input itself.
If the probe is in line after the integrator (between it and the scope), the capacitive loading has no effect because the integrator output is low impedance, and it adds 20dB loss. In this case, the probe neither adds nor subtracts nothing. It's better to just use a BNC to BNC direct cable.
...unless there is something going on that I don't know about.
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Post by stratotarts on Apr 3, 2022 20:02:10 GMT -5
The first one looks like the integrator bypass switch was accidentally selected, disabling the integrator. Just a guess. The second one, I would need more details. The images you posted don't show any electrical connections. What wires are provided from the pickup? Which ones did you connect to? Can I see a photo of the test setup? Sometimes loop gain problems can distort the plot - from clipping due to overload, or excess noise due to insufficient drive from the test coil. Please watch the o-scope display during the test and look for signs of trouble there. It's visible during the plotting process.
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Post by stratotarts on Mar 10, 2022 9:18:13 GMT -5
The lowest capacitance range on the DER is 200pF and the specified resolution is 2%. That's 4 pF, and also it's recommended in the specs to do an open/short calibration before performing measurements on that range. It might not be practical or necessary to routinely measure pickups to such accuracy. Just take it as a close measurement, limited by the expected error.
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Post by stratotarts on Mar 4, 2022 14:43:44 GMT -5
I agree, I have seen this kind of result from signal chain overload. Try monitoring the waveforms visually during the peak readings. I think you will see some distortion there, which you can fix by adjusting the levels in your signal chain.
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Post by stratotarts on Feb 27, 2022 13:32:13 GMT -5
One thing I'm curious about - I tested non-active plastic housing HB's a while ago. Those were direct purchase from Asia. One huge disappointment about them, in spite of epoxy potting, they were horribly microphonic. When I cut them open I found incomplete potting. My question - are these fakes subject to the same flaw?
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Post by stratotarts on Feb 27, 2022 13:13:40 GMT -5
The plot you posted looks completely wrong for any normal pickup. Something is definitely very wrong with your setup. If that is a plot of an input-output loopback it is also completely bad. Please post more information in order to get help. Which measurement circuit are you using, and what component values?
Unless you are just showing us the plot with the monitor switch engaged...
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Post by stratotarts on Feb 24, 2022 8:33:56 GMT -5
What software are you using to make the sweep? Also, on the FocusRite, the "input monitor" selection must be turned off. If not, some of the pickup response is fed back into the test coil and disturbs the readings.
Also, I can't see your gain settings but you also need to verify that the sine waves at the input are not clipping (that the input is not saturated). Rightmark displays the input on a scope in real time for that.
Otherwise, you are correct, you should see a virtually flat line.
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Post by stratotarts on Feb 21, 2022 19:15:58 GMT -5
Holy cow! I had no idea that was out there! That's a really useful video, and well produced.
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Post by stratotarts on Nov 17, 2021 8:03:24 GMT -5
Under the brushed nickel plating on the covers, is it nickel silver or brass material?
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Post by stratotarts on Nov 12, 2021 10:08:42 GMT -5
Is the answer just to lower the wind count Yes. It's the most influential factor.
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Post by stratotarts on Jun 20, 2021 11:26:43 GMT -5
Your schematic appears to be behind a registration wall. Could you possibly move it here, or host it publically?
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Post by stratotarts on May 24, 2021 21:08:25 GMT -5
Thanks for the test and teardown. I don't get much chance to do it any more, time constraints and no theories to test at the moment. The more people publish tests, the more robust the entire process becomes.
It's not necessary to fully surround the pickup with shielding material while testing. Of course, if it works for you, it's harmless. I've found that a sufficiently wide ground plane under the entire test area provides more than adequate shielding. It's possible that some environments have strong RF fields, that's the only thing that might be an exception, but I've never encountered any problem like that myself. In the early stages of development, I thought I would need a fully closed box and drove myself crazy with parts from the hardware store. It was a relief to find that in practice I didn't really need it. Interestingly, I just ran across a commercial product for ham radio equipment, that functions exactly the same way. It's a half desk sized copper sheet that you ground, and place all your radio equipment on - said to reduce interference from stray electrostatic fields around the wires. So, working exactly the same way. Any sufficiently large conductor creates an electrostatic "shelter" around it, the closer to it your equipment, and the wider it is, the better. My ground sheets are about 12" (40cm) square.
Magnetic hum can not be stopped by any normal kind of metal shielding, it's possible but uses esoteric materials like mu-metal. The best thing you can do, is rotate the pickup around and try to null it out. Usually the interference is directional.
Apart from the blade instead of pole screws, the other difference from a P-90 is that the coil is tall and thin, where the P-90 is famously wide and short. I think a genuine Charlie Christian pickup is on every tester's wish list.
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Post by stratotarts on May 23, 2021 8:17:57 GMT -5
Yes, you got the tester from me. Everything looks fairly normal there, but I see some small issues. The test leads are backwards - green lead is ground and should go to the pickup shield, gray is hot and goes to the pickup wire center conductor. That may introduce more interference, and skew the capacitance reading. I'm not sure if you moved the shield for the photo, but it should be underneath the integrator, the test wires and the device under test. I use the same foil, between sheets of thin cardboard to prevent shorting. You can definitely see some mains hum in the plots - present at 60 Hz and 180 Hz, the second harmonic. Some of that might also be the normal magnetic hum common to single coil pickups. But it looks quite strong. The results look quite believable for a CC style, the eddy current losses are visible in the "droop" and the numbers, the result of a lot of steel parts in the string field.
The spreadsheet is nominally colour coded - yellow are input numbers, pink are intermediate calculations or constants, and green are output values. You can ignore and omit the last 5 columns, they are just sanity checks or numbers used in some special studies.
Generally, my first thought would be to compare it with a P-90.
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Post by stratotarts on May 18, 2021 19:45:59 GMT -5
I've always thought tarnished brass covers would look great on a steampunk themed guitar...
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Post by stratotarts on May 3, 2021 13:36:08 GMT -5
You're showing me two measurements showing one resonance at 4703 Hz and another at around 2600 Hz. You're claiming that the inductance is the same? It's almost physically impossible so I respectfully doubt the integrity of your measurement technique. Especially lacking details - I've certainly been wrong before, but so have others.
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Post by stratotarts on May 2, 2021 20:50:51 GMT -5
Still it removes variables from the measurement. I apreciate that some manufacturers publish resonant frequency data but they sometimes forget to tell under which load. I'd take Henries over that. Expressing Q at a fixed frequency independent of the resonant frequency sounds confusing, I don't think I've seen a pickup specified like that. It may be confusing, but a clear explanation based on a fallacy isn't particularly useful either. The Q at the unloaded resonant frequency doesn't really mean much, as in the guitar it doesn't resonate there. I don't consider it meaningful that some method or other hasn't been used or popularized. It comes down to this - every meaningful and repeatable measurement and specification system must convey (either intrinsically, or through some kind of interpretation) some information about the perceived sound (tone). One should not be made to sacrifice the other, but it often happens. In my results spreadsheets, I have a column for "loaded resonant frequency" and "loaded peak amplitude" which are bluntly visible on the Bode plot, and lend themselves readily to easy translation into the experiential realm (what does it sound like?). The two dimensional tonal map resulting from that characterization has been demonstrated in a thread here, and is fairly easy for a non-technical person to grasp. It's just when the buzz words start flying around that people who are not versed in the lore, tune out or even express a lack of confidence.
The parameters that ms mention, correspond very closely to the ones I use, the only difference really is the test frequency. There is an almost one-one correspondence between those and between the meaningful and recognizable features of the plot that I use. Since the resonant frequencies and Q given a fixed test load capacitance, and the same measured at 3kHz are not greatly different, the only issue is which is the best way to achieve test standardization. A fixed frequency would do that, and the sonic effects of the resonant frequency and Q under a fixed load would not usually be very different. The entire thing is too baffling for the average player, they don't care much about how the numbers are produced, just that they can gain a hands on experience with the numbers after listening to and reading the specs of many different pickups. So they don't need to know anything about the test frequency. Just "L=2.8H, Q=1.4" and if the industry is smart enough to use a standard frequency like 3 kHz, they don't have to understand it, just benefit from informative and accurate measurements.
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Post by stratotarts on May 2, 2021 20:11:14 GMT -5
ideally 100/120 Hz, whichever doesn't pick up line noise 50/60 Hz in their country This is different from what I've read: The inductance should be measured at 1000hz as some pickup designs measure a higher inductance at lower frequencies relative to higher frequencies. And I surmise that it makes sense, given that Henries alone should give you some idea of how the pickup performs in the treble. It still does. The difference is in the 10% range at most. That's barely audible. But I think looking at Henries alone is not really sufficient. I really like ms's suggestion of specifying inductance and Q at 3kHz. That sort of "cuts to the chase", as it represents the fundamental factors that dictate the measured values of my "loaded resonant frequency" and "loaded Q". I think those could be derived from a simple Bode plot of the response, but as each pickup does have a different inductance, either the test capacitance would have to be made variable to hit 3kHz, or some mathematical transformation would have to be applied to the values measured with a standard load capacitance. I'd be the first to admit that kind of math is beyond me.
Also consider the danger - if nobody can agree on a test frequency for inductance, and also fails to publish it, it's not worth as much. I should take some comfort in what you say, considering that my integrator device has an inductance test setting that usually tests near 1 kHz. But I've been telling people that it's an approximation because of the difference. Now the story is more complicated. This sort of thing is why I've mostly dropped out of research to concentrate on manufacturing and supporting the integrator. I just don't have the time to keep up with everything.
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Post by stratotarts on May 2, 2021 16:05:20 GMT -5
Specs can also be used to baffle brains... you mentioned something there that reminded me of that right away - I've seen the resonant peak given as a specification. By itself, unloaded resonant peak frequency is a relatively unimportant spec because of the fact that it is mainly influenced by inductance and capacitance, inductance is not altered by the guitar circuit very much but capacitance definitely is. But the capacitance is always significantly overshadowed by the guitar circuit capacitance. Hence inductance by itself, although it is a much simpler data point, is a far more revealing aspect that tells you far more about how it will operate in situ than resonant frequency ever will. But it sounds really knowledgeable and technical so someone can pretend to be giving out specs when in fact almost nothing useful can be learned from it.
If there is ever a useful "lingua franca" that everyone could use to characterize pickups technically, besides the general construction and type, it would be inductance, loaded resonant frequency and loaded Q. A standard load doesn't exist in the industry, around here we kind of settled on 200k/470pF because it's pretty close to most guitar circuits. That would be a problem in an industry that has no governing body or professional association to organize standards (such as IEEE). It's the 2 dimensional map produced by loaded resonant frequency and Q that mainly defines pickup tone differences. Most other specifications and details are inputs into those characteristics. Thus there are often many ways to target the same data point in that space.
But it would be a huge step, really the first step, if manufacturers would begin listing the inductance and preferably also the frequency at which that is measured (ideally 100/120 Hz, whichever doesn't pick up line noise 50/60 Hz in their country).
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Post by stratotarts on May 1, 2021 20:58:07 GMT -5
There can never be too many testers. Also robust discussions have not generated a "right way" to test. Instead, a field consisting of different programs and investigative focii has evolved. It is like a smorgasbord of concepts and techniques that you can use. When I started my investigations in 2014, it was apparent that such work existed, but was fairly rare and isolated (meaning not much feedback and interaction amongst researchers), also scantily published. Here we are in 2021 and I see a tremendous interest in the subject, not just from people approaching it from technical interest or curiousity, but also from pickup manufacturers. I never reveal any specific information about individual customers, but I can tell you that many commercial pickup makers now have my device. In my conversations with them, it's clear to me that they accept the validity of the tests and want to engage in the technical aspects of testing that will assist them in design and manufacturing. Before my device came along, some of the big ones had the Lemme integrator. I've seen one in a published photo taken on a factory tour.
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