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Post by stratotarts on Mar 4, 2024 18:36:03 GMT -5
You have to find the premise very important (a pickup that has multiple voices). It's at least interesting and may be useful to someone. If that feature is valuable to you, they might be the right product for you, notwithstanding the hype. There's no mystery about coil switching, it's been going on for many decades. Many people find it unnecessary, if you want different voicing, it's possible to just collect more guitars. A lot of people do that anyway, and as a bonus you can match the pickups to a unique body/neck in each case. Even from big name manufacturers, you could get great conventional pickups for less than that kind of money. Often the real reason for something new is that the manufacturer has run out of differences with other manufacturers products, need something to differentiate their products. Pickup design is so worked to death that it's hard to do anything really new that is really worthwhile.
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Post by stratotarts on Mar 4, 2024 16:47:34 GMT -5
It's stated in that document that Q should be defined (so I suppose measured) at the resonant frequency. I usually consider it that way, but I'm aware that it's not quite right, you can measure it at any frequency. Some people talk about Q at some standard frequency, for example 1.0kHz. The difference and the discussion should be about why, and what exactly you are trying to measure, describe or specify. I have personally avoided using the term, instead talking about peak amplitude because it's the effect that I believe will be most audible. If you have a polar plot you can calculate Q at any frequency, but it's meaningless without the reason and context. For comparative purposes you do have a good rationale for using a standard frequency other than the resonant, but it's a different purpose, and the two values are closely related anyway.
It's amazing that so many people (who also pose as experts) get shielding wrong. Or, only partially right. Even Bill Lawrence's published treaties start off on the right note but seem to go sideways and miss the simple well known (to engineers anyway) difference between magnetic and electrical field interference. Quite a few "experts", like the late Bill L. did, continue to claim that aluminum blocks magnetic interference well. It does not. If it really did, you would see it performing that function in all kinds of crucial professional electronics going back 100 years now. But you don't. There is only mu-metal but even it doesn't act as a simple block.
A big factor in the inaccuracy of published information in the field is the effect of the isolation of designers from information carefully protected from any public view for proprietary reasons. The only reason that has significant cracks in it now, is that the internet exists and people have more chance to view a lot more and a lot more varied information.
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Post by stratotarts on Mar 4, 2024 15:58:19 GMT -5
One little puzzle is the USD$85 extra for the noiseless "option". You have to go to the purchase page to see that. Not sure if I missed any explanation on the main page but all that I think I read there called them bucking or noiseless. My honest and full reaction to that kind of vague adjective filled ad copy is best kept offline. Again sad to see a manufacturer withholding meaningful specifications while indulging in pull-out-of-the-hat jargon and superlatives that must mean 100 different things to 100 different people. It's a double shame because they're probably pretty good pickups, not junk. So the hype is so unnecessary. Again. They and many others will keep doing that, and keep saying those things, as long as people fall for it and continue to purchase stuff based on those kinds of descriptions.
It's especially weird when the descriptions contradict the attributes that produce them. They are described in one configuration as both fat and clear. Well fat implies a fairly low frequency response and clear implies a fairly high frequency response. It's like calling something bright but dim.
From the site - "with a very fat but clear low E string" which does describe a sub part not the whole but we know there is no special isolation around the E string...
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Post by stratotarts on Feb 23, 2024 11:29:30 GMT -5
Welcome, and thanks for the contribution. To fully utilize your measurement information, people will want to know the details of your measurement system. That is because different equipment configurations may yield different results. It's not strictly necessary to have bode plots, but helpful.
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Post by stratotarts on Feb 16, 2024 15:51:59 GMT -5
The magnet must be Alnico. Can you be more specific, "reverse polarity on the bridge pickup"? What do you mean? BTW some Ibanez also have the RWRP split coil configuration using HB in one switch position, IIRC.
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Post by stratotarts on Feb 16, 2024 15:40:10 GMT -5
What are the questions you mentioned?
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Post by stratotarts on Oct 17, 2023 14:30:13 GMT -5
Is this a learning assignment, i.e. school project? As a science experiment, it starts out on the wrong foot because it sets out with a dubious premise - that pickup capacitance greatly affects the tone. That isn't the case. You should do some preliminary research to find out what the actual major factors are, so that your experiment will be meaningful, and also easy to perform with simple equipment. That research will also give you adequate context to explain your findings. I suggest you do that, and re-frame your experiment.
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Post by stratotarts on Sept 18, 2023 11:09:49 GMT -5
The point of looking at the high frequencies would not be to know what it sounds like, but to determine and verify the effects of an appropriate load. I suppose if the stock pot values are 2.5k as you say, you could test using that (or half that, since the tone pot is in parallel), and examine the first 20kHz like usual. My expectation would be almost a flat line across the entire audio spectrum, however the magnets characteristics will probably bend it a little. With low impedance pickups, the plot is always going to be very predictable because the resonant frequency is so high. If high fidelity was really what people wanted to hear, modern pickups would probably be mostly low impedance because they would satisfy that requirement, and would also be easier to wind. Output isn't nearly as important as it was before high gain transistor input stages became commonplace. There's also the fact that high impedance (normal) pickups are in an ecosystem of amps, pedals and effects that inter-operates mostly seamlessly. Hence the use of impedance matching transformers or preamps.
You may be aware, there is an entire forum dedicated to low impedance pickups, small wonder due to their special properties. If an audio engineer naively designed pickups, they would be low impedance because they are flat. But, everyone has gotten used to the low pass filter response, it produces pleasing tone, so there isn't much demand for flatness. You can see examples of marketing aimed in that direction - "wide range" humbuckers from Fender, and the Betts "high fidelity" Filtertron design for example. Yet neither of those actually exhibit flatness, so it's a kind of doublespeak or "playing to the crowd".
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Post by stratotarts on Sept 18, 2023 7:35:38 GMT -5
Put the pickup faces together. If they attract, they are RWRP. If they repel, they're not RWRP. Because, for RWRP, the magnet polarity must be opposite.
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Post by stratotarts on Sept 17, 2023 21:14:06 GMT -5
It would be better to use some other arrangement like an impedance bridge, first focus on finding the actual self-resonant frequency, then try loading with a few low values between 600 ohms and 10k ohms. I agree that the resonant frequency will be very high, for this reason the load for a normal kind of resonant peak is hard to calculate, some iterations of testing would probably be necessary to extract really revealing data.
If you have the "original" impedance transformer, it would be nice to have measurements on that too.
A local jazz player has one, he let me hold it but not play it. I asked, really just to have a closer look at it. He was really nervous about it, I would be too.
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Post by stratotarts on Sept 17, 2023 19:07:16 GMT -5
It's exactly what you would expect from P90's. I'm curious, were they RWRP?
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Post by stratotarts on Sept 15, 2023 9:47:23 GMT -5
It's true that the excitation signal does not have to be a sine sweep. But I was speaking in the limited context of the Rightmark software in particular. I don't think it has the ability to use tests like the multi tone for the purpose that you describe. Are you referring to the roll off, above or below 100Hz? Or both? The roll off below 100Hz is a normal artifact of the integrator response, and also the response below 100Hz is normally not interesting (i.e. it's virtually the same for all pickups). So my plots, at least, don't include any information below 100Hz unless I am testing the integrator. However, the roll off between 100Hz and the resonant frequency, is suspicious and the remarks I made about test signal levels were directed at that. It could be a sign of too low, or too high, test signal levels, a result of either noise, or distortion components respectively. A typical humbucker plot does have some of this "rise" but it seems a little too much in this case. It would be interesting to see a plot of some known pickup that I could compare to, using the same test set up. It's possible that the "rise" is visually exaggerated by the inclusion of 10Hz-100Hz, too. So a normal plot but expanded. Here is a wide range test plot to show what I mean. The middle (blue) plot is loaded. You can see only sub-1dB difference in the flat region.
Looking closer, even more pronounced flatness. The two peaks show the effect of clipping on the test signal - the peak amplitude is reduced:
In the plot posted in the first message, the amplitude begins to fall off above 100Hz. That is suspicious. It's possible that the audio device used as an interface, is not configured correctly or does not have an adequate low frequency response.
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Post by stratotarts on Sept 12, 2023 17:32:42 GMT -5
Just FYI, a multi tone test is meaningless for pickup measurements. It's designed to analyze intermodulation distortion as the result of non-linearity in the response. If the tests are conducted with correct signal levels, there should be no measurable distortion or non-linearity. The sine sweep is the appropriate method in this case.
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Post by stratotarts on Jun 16, 2023 22:53:40 GMT -5
That's perfectly acceptable and a good thing to know. Thanks for the measurement. I've experience, people have different preferences about how to connect, and I'm trying to find a way to accommodate most of them. The bare wires I have now are that way for the necessity of the least possible capacitance. In the beginning of my investigation of the subject, that seemed necessary. I provide it subsequently because it's proven and has good accuracy. I am considering the terminal strip for that reason, that people can more easily attach whatever they like to it.
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Post by stratotarts on Jun 16, 2023 21:50:53 GMT -5
The calibration adjustment does not compensate for variable capacitance present at the input leads. It is intended to compensate for (and isolate mostly from the measurements) the op amp circuit input impedance.
It is a nice build, the input capacitance I was worried about comes from the connector itself and also any coaxial cable attached to it, not the wiring to it. Capacitance is determined strongly by surface area, as the other factors like distance between "plates" are similar, it takes prominence. I have built models with banana jacks, but didn't have a chance to measure the difference in capacitance. I do consider at least visually, or from a design standpoint, an estimate of the small capacitance which is not usually specified by the manufacturer because it is not important in the applications they are used in. For example, a BNC connector might usually be used with coaxial cable, in which the capacitance is mostly nullified by it's inclusion into a transmission line. But coaxial line becomes mostly capacitive when it is used well below radio frequencies, e.g. audio.
However also, your implementation has two parts, the BNC jack and the BNC plug/test clip assembly shown. I would judge, more capacitance due to the assembly then the jack if used with a bare plug. In truth I want to move to a screw terminal strip arrangement for test leads.
The calibration of the input network is done from a low impedance signal source, such that only the in circuit capacitance value of 4pF is compensated. But there is no practical way that I know of (at least any simple way) to compensate for additional parasitic loads that exist, at least in a direct measurement input circuit. If you are taking numerical measurements you can compensate for it mathematically later on.
Typical audio line level drivers and loads are designed to minimize the effects of that capacitance (hence why you may not see pF specs for a BNC or audio connector). A pickup circuit has too high an impedance to be similarly insensitive.
I repeat, the sensible thing to do is measure it. My target input capacitance is 10pF which includes the 4pF input load and 6pF stray capacitance. It's on the low end of the scale that I can measure, but I have done that and it is close. If you know the input capacitance you can simply add it to your calculations. In my spreadsheet, that is how it is done. The estimated or measured input capacitance is entered in a cell in the sheet. That value is subtracted when pickup calculations are done.
There is inevitably some capacitance, and it is worth considering that the capacitance of the pickup which is much greater, is still yet much less than the capacitance of the entire system. This means that it may have more analytical than practical value.
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Post by stratotarts on Jun 16, 2023 13:08:55 GMT -5
Josh, that looks good to me. A more certain analysis requires setting up reference markers on the scope. For example setting one horizontal marker to the 200Hz level, and setting the other marker to the tip of the peak. Then you can read off the numerical difference. It's also more revealing if you can superimpose the loaded and non-loaded plots.
I see that you have installed an input jack on the integrator. I specifically avoided that due to the increased capacitance, but it is small, and if you measure it you can factor that into your calculations or conclusions.
I'm not sure from the image, but it looks like maybe your input gain is set to 0dB. Normally, it is better to use the -20dB input gain setting as it has proved to fit the dynamic range of most measurements better.
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Post by stratotarts on Jun 5, 2023 20:47:08 GMT -5
It's been a while since I looked at the passive (simple) measurement procedure so I looked up the thread. The circuit with the test coil and 10x probe is the one you're using, I assume? That should be okay. The integrator closely duplicates a 10x probe in its input circuit, to make it possible for people who don't have a scope to do it (at the moment it now appears that the majority of people are using scopes anyway...). The response would be the same as a scope, when the integrate/bypass switch on the integrator is set to "bypass".
It is with the impedance measurement that some conversions have to be made to the resulting data, because it can't be done without some resistive load. That is the one I was worried about but I guess you are doing the other one with the test coil.
Since you're asking about the plot, it looks to me like some interpolation has missed the top of the peak, causing it to be chopped off. Perhaps you need to adjust the settings to capture more data points.
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Post by stratotarts on Jun 4, 2023 16:38:04 GMT -5
Not sure what you mean, "tested directly".
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Post by stratotarts on Jun 4, 2023 16:32:25 GMT -5
Are you connecting the pickup directly to the scope input, with no 10x probe? That will place a 1.0M ohm and about 15-30pF capacitance in parallel with the pickup. Also, in the first message you refer to "your bode plots". Whose bode plots, or which bode plots, are you referring to?
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Post by stratotarts on Jun 4, 2023 11:45:02 GMT -5
What is your test circuit?
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Post by stratotarts on Jun 3, 2023 20:04:40 GMT -5
Josh,
First of all, I think you should really check out the GuitarFreak program. It performs a lot of the math that you mention, and incorporates many rounds of alignment with theoretical and empirical measurements, such that it has become very good at estimating the actual in circuit behaviour of any pickup, given its test measurements.
Also, many years have passed since the test apparatus in use, has any appreciable load on the DUT. The V5.8 integrator, for example, places about the same load on a pickup under test, as a short length of connecting wire. So that objection is mainly rhetorical in nature. We are talking macro scale electronics, not quantum mechanics.
Overall, what comes to my mind, is that what makes this forum unique, is the adherence to the presentation of the results of actual experiments, wherever theoretical ideas are put forth. If you find the current state of experimentation lacking, the best thing to do is to do some experimental work and post the results here, so we don't get into purely theoretical or rhetorical discussions.
In fact, most of your doubts have already been entertained and dealt with here on this forum. It's just hard to dig up sometimes because the ideas and projects presented here go back many years. Also some of the procedures you suggest, are already in use by many people. But, your main idea, which is to allow the interpretation of in circuit performance exclusively from test data, can be and often is done using GuitarFreak.
Once someone gets a good grasp of the circuit behaviours, it is even feasible to quicky mentally estimate the final in circuit implications of some test result.
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Post by stratotarts on Apr 23, 2023 19:32:39 GMT -5
That is right, the statistical significance is not high, given the limited sample size. Which doesn't mean it's untrue, just not very conclusive. I once worked in a factory which had 10 or so testing stations. The number of false DUT failures (thus no fault of the DUT, passes on re-test) per shift numbered in the 0-3 range. We were expected to take immediate action as soon as even one failure occurred. But, this was physically disruptive to the stations, due to RF sensitivity to component orientation. I argued for a more targeted approach that would track over several shifts and identify stations that needed adjustment. This was vehemently rejected.
So, I wrote a simple spreadsheet program that assigned failures randomly to 10 imaginary stations. The results looked exactly like a typical shift. I took those to my boss and pointed out, each station is absolutely identical and yet it appears that some are faulty. On every subsequent run, the distribution was different, as you would expect. I suggested, after repair work, some stations might actually have degraded performance. This was met with scorn. The sun really doesn't shine in the place where their heads are. Thank heavens I'm not involved with that stuff any more.
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Post by stratotarts on Apr 22, 2023 21:28:14 GMT -5
I think it's safe to say, it's the cover. The losses are too extreme for the baseplate alone to account for it. They're close to measurements done on other brass cover PAF clones.
A thought - such a response might be perceived differently depending on whether or not there is anything else to compare with. If so, then the drop in treble might trigger some biases, if not, some twiddling of some knobs might find a sound that a musician might find pleasant. In addition to the fact that the subjects were invited to make value judgments, which are obviously going to be influenced by their musical styles.
If I were designing that experiment, I would instead ask them simply to identify them by A-F or whatever. Still some bias, but not begging for it. I didn't follow the entire presentation yet, so I'm not sure. I think it's at least significant that there is correlation between the pickups and the subject ratings, the likely brass covered one that is verified in the plots, was spotted by the participants.
But it also illustrates a problem, when asked for preferences, now from the results you don't know was it, "this pickup is the smoothest/dullest on a scale of 1-5" or was it, "I really like the sound of this one" - which is the question you have been asked. In a way you've done also a survey on preferences, as well as pickups.
I would think, a pickup maker would find it handy to have some data on what people are asking for when they ask for, "a smooth" or "a dull" pickup for example.
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Post by stratotarts on Nov 24, 2022 20:51:35 GMT -5
Two interesting things that actually support each other... the HP probably does not have any integration method. Hence (my theory anyway) the reason for the world's largest test coil, with what appears to be a several kilogram steel core. The huge inductance is necessary to provide an integrated response, the same way that Moore did it. I think Moore's coil was not so physically large though. I wonder how that affects the accuracy? Everyone here has bent over backwards to try to make the test coil essentially invisible.
Also, the plot has the appearance of a linear plot with frequency vs. the log frequency plots that almost everyone else uses. Both things seem like "had to be invented here" syndrome in play. Which from a PR perspective, makes perfect sense.
Note also the apparent lack of simulated load.
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Post by stratotarts on Nov 16, 2022 11:07:56 GMT -5
I agree, but this will give you a comparison between a SC and one coil of an HB, when only one coil is excited (the other one is weakly excited, however). I think you would have to consider the excitation of both coils if it is an output comparison that you are doing, since the string does excite both coils of an HB.
I can't help but wonder, though, what is the purpose of comparing them? Is it, for example, making matched sets of HB/SC for some guitar? It is already common knowledge that HB are louder as far as I know. A really meaningful comparison depends on a reasonably accurate measurement. To make that work would require an exciter test arrangement that can be confirmed by comparison with actual string driven measurements. Also in this case, that would accommodate diverse pickup types. It's possible but not very easy. The problem is not to make it work, but to determine the measurement error confidently.
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Post by stratotarts on Nov 15, 2022 20:00:57 GMT -5
Anyway, I'm confused because I measured the rail pickups with the coil standing on its side inbetween them, as I do for all humbuckers, as you taught me -- but I can't imagine that would cause them to plot so much lower than the Strat pickup. That was very confusing. The rails and poles in both cases were uncovered, exciter coil just directly on top of them. Magnetic fields decay very rapidly as the distance from the source. You can check that with the magnetometer. There is a huge difference between the field intensity at the pole tops, and a point a few millimeters away from that. The time varying string field isn't the same field, but it follows the same general rule. So it's much more intense at the poles than slightly distant, just the same.
Yes, it's next to "save image". IIRC it doesn't say "CSV", it only mentions "data".
You could. It makes me a bit nervous because of the risk of clipping. Seems to me that would be an awkward trial and error process anyway. I now use a 4Vp-p drive because it gives me the best dynamic range. But I monitored the signals a lot to be sure that was safe. Testing at a fixed drive level, exporting and doing post processing would be preferable.
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Post by stratotarts on Nov 14, 2022 16:41:05 GMT -5
Just a quick note for now - a 19.8dB difference is suspicious because the integrator has a 20dB gain switch on the panel. Is it possible you bumped it accidentally? Also to leave a thought with you that might steer you to the answer to several questions that you asked ... many people export the scope data as a .CSV file and then process it in some other software (like a spreadsheet). With that, you can program almost any plotting or analysis you can dream up.
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Post by stratotarts on Nov 14, 2022 8:32:16 GMT -5
What I'm looking for is an explanation for the lower frequency range response varying significantly between all three examples, and what it would actually mean in practice, tone-wise. That range is dependent mostly on the efficiency (output) of the pickup. But that is not a dependable measurement unless you carefully maintain the same dimensional characteristics of the test setup when testing multiple pickups. If you test the same pickup each time, you will see that the ~100Hz amplitude never changes more than tiny fractions of a dB, for any load changes that are non-resistive. If you are comparing different pickups with different output, it will raise or lower the ~100Hz base line, and also the entire curve. In some sense, the output is not a tone parameter (for example if you set all the sliders on a multiband eq up 3db, it's still "flat"). A lot depends on how you interpret your data. Certainly it is important to know whether the comparisons are of an absolute level, or "normalized" to consider the tonal response.
Often when I am comparing pickups with different output, I manually normalize the plots so they overlap at ~100Hz, just so the tonal differences are easier to view. An absolute, or non-normalized plot may be useful, but it is important to decide what meaningful direction the interpretation should take. Also, if there was a between pickup test setup change, it should be regarded as uncalibrated unless specific steps were taken to maintain minimal deviation in the test apparatus, and that deviation is itself known through calibration and experiment.
The main (possibly only) thing that output changes, is the way it exercises non-linear responses downstream, like effects boxes and amp inputs. Because, they may have non-linear response to inputs. However as both the guitar settings and input sensitivity and non-linear characteristics vary widely, it is difficult to predict the in situ effect of the loudness of a particular pickup. That is why I don't pay much attention to it, in the context of Bode plotting or tonal determination. I think, the output factors into the actual sound in a way that is a combination of output and tone, but the way those can be predicted is different and has different outcomes (for example depending on clean vs. dirty amp settings).
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Post by stratotarts on Nov 12, 2022 14:57:16 GMT -5
The problem with this, is that you haven't explained how you obtained the "EQ curves". Also it's not perfectly clear whether each or both curves are EQ curves or Bode plots.
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Post by stratotarts on Oct 10, 2022 8:41:54 GMT -5
No, "headroom" refers to the safety margin in the dynamic range of a signal channel, that allows transient peaks to pass without significant distortion, above the average or nominal signal level. What you are talking about is just "dynamic range". But since all pickups are basically linear transponders, the dynamic range you describe pertains to the actions of the player, rather than the pickup itself. The pickup itself has no dynamic range that is a useful metric. Technically, the dynamic range would be the ratio of the thermal noise in the wire, to the limit reached when the voltage in the wire is high enough to break through the insulation, or the current is enough to melt the wire, whichever comes first. Obviously this is not a useful metric since it never happens.
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