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Post by antigua on Nov 24, 2019 17:54:23 GMT -5
I've measured with the sensor pushed against one of the pole pieces, unfortunately the lineair range of the sensor only goes from 0 up to 670 G. Could you buy a hall effect sensor with greater range, or would it be a lot more expensive? The decent Chinese meters are about $110, I'm wondering what it would cost in total to construct a similar device with the same range. I wouldn't be surprised if a fancy hall effect sensor is the reason they cost as much as they do, but then I would be surprised there aren't some cheaper models with lower sensitivity. |
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Post by perfboardpatcher on Nov 25, 2019 14:00:40 GMT -5
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Post by andrewbrown on Nov 28, 2019 6:21:56 GMT -5
Thank you for posting this! Do you have a detail explanation regarding this schematic model? I would like to understand it better. The why and how it was modelled. Many thanks!  Regarding pots and caps, I understand that changing values will affect the resonant frequency and Q factor of the pickup curve. What I'd like to study now are the following: 1. How much change in Volume Pot resistance is needed to hear any difference in sound/tone? i.e. If I have 2 pots rated at 250k, having the actual values of is 247k and 251k, will the sound differ? (assuming volume pot is at 10). Or do I need a drastic change, say from 250k to 300k, or 250k to 500k in order to hear any difference? 2. Similar with the pots question. How much change in Tone capacitor capacitance is needed to hear any difference in sound/tone? i.e. If I have 2 caps rated at 0.047uF, having the actual values of is 0.045uF and 0.049uF, will the sound differ? (assuming tone pot is at 10). If not, will changing the value to 0.033uF or 0.022uF give audible result? Or is the effect more felt when the tone pot is being rolled down? 3. I'd like to understand how different capacitor types (mylar, ceramic, orange drop and paper-in-oil caps) affect the overall sound. If I have different types of capacitor having the same values. Will they sound any different, and why? Is the difference because of tiny difference in actual capacitance values or is it because of different dielectric materials? Thank you! Regarded strictly as a signal filter, guitar pickups are RLC networks with both series and parallel resistances, so the basic model is basically nothing more than that, and it's rather accurate. But then the steel parts in and around a pickup cause eddy currents, the relationship between the eddy currents and the guitar pickup is the same as the relationship between a primary and secondary coil in a transformer, and so it can be modeled with LTSpice as a transformer. You don't really have to model all of it, just know that pickups with steep part, like screws and slugs will have a much lower Q factor than the simple pickup model indicates. With a PAF type humbucker, the steel causes a loss of Q factor comparable to putting a ~100k resistor in parallel with the pickup, so it rounds off the high end response of the pickup quite a bit. As said above, how you will know if you can hear a difference is if the amplitude changes by more than 1dB. 1dB to 2dB +/- not very audible, but a 3dB difference should be easily heard. If the resonant peak of the pickup is high, 5kHz and beyond, it will surpass the operation range of a guitar speaker and probably won't be audible. The lower the peak frequency, the more likely you are to hear the difference in the Q factor. If the tone pot is at 10, the cap value is effectively irrelevant. As you roll it closer to zero, the value matters increasingly. The differences between 1nF and 100nF is easily audible, but outside of that range, you won't hear much difference, as below 1nF will attenuate too high of a frequency, and beyond 100nF too low of a frequency. 22nF and 47nF are the standard values, but you can use 100nF to get a supper muddy tone, or 3nF to get a thick humbucker/P-90 like tone from single coils. The capacitor dielectric doesn't matter, so long as it's not electrolytic / polarized. The difference between film and ceramic doesn't matter at low voltage audio frequencies at indoor/outdoor temperatures, but in general, film caps are more reliable; they're usually more accurate, less microphone and have a more linear capacitance-by-voltage curve. I don't think the difference is audible, but I've never really tested it specifically. I don't know of anyone ever, in the history of the electric guitar, being able to guess the cap type just by listening to the guitar. |
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Post by pablogilberto on Jan 16, 2020 8:26:15 GMT -5
This effectively becomes a metallurgical analysis, because when you see the steepness of a peak drop, it means that you are seeing eddy current losses caused by the metal used in the construction of the pickup. The reason the Donlis has a lower peak than the Tele bridge pickup is because the steel used in the humbucker has a higher conductivity and permeability than the AlNiCo in the Tele bridge, and higher permeability and/or conductivity means more eddy current losses. This method therefore allows you compare the qualities of various metals used in the construction of pickups. A high DC resistance in a pickup will also reduce the Q factor somewhat, but if the DC resistances of two pickups are within, say 25% of each other, and you see an obvious difference in Q factor, the cause in this case will be the eddy currents in the metal parts. A counter example, would be two pickups that are alike but have very different DC resistances, for exmaple an Seymour Duncan SSL-1 has a DC resistance of 6.5k, while the SSL-5 has a DC resistance of about 14k, but both pickups have all the same parts otherwise, the SSL-5 has a lower Q factor because it's DC resistance is more than twice that of the SSL-1. Eddy current losses and DC resistances have a similar, but not exactly the same, effect upon the Q factor. Note that AlNiCo magnets are metal, and therefore subject to the same qualities of permeability and conductivity as the rest of the metal used in the pickup (mostly steel). Ceramic and neodymium magnets are special in that they are neither permeable, nor conductive, and so they are like air, in terms of their electrical effects. AlNiCo has a much lower permeability and slightly conductivity than steel, so if you take a Strat pickup, remove the AlNiCo pole pieces and replace them with steel pole pieces, the pickup's inductance increases by about 50%, and the Q factor also drops by about 50%, and this largely what sets AlNiCo Strat pickups apart from AlNiCo Strat pickups, not the ceramic magnet underneath, as is generally assumed. When a pickup has a lower resonant peak frequency, as the Fender Tele bridge appears to have based on the plot, it must mean that it has a higher amount of inductance and/or capacitance. If you purchase a good LCR meter, such as the DE-5000 (set it to measure "L" with series losses "SER" mode, and the lowest test frequency possible, 100Hz or 120Hz), you can determine the inductance of the pickup separately, then it's easy to work out the capacitance specifically with an online calculator, by entering the resonant peak and the inductance value. Similarly, an LCR meter like the DE-5000 with a very high test frequency (a minimum of 100kHz is recommended), the capacitance can be measured (set to measure "C", assuming parallel losses "PAR" mode, and the highest test frequency available), and then from that L and C you can determine the resonant peak with the same online calculator. There are many other uses for this pickup testing technique:*** You can compare two or more pickups to find which pickup is hotter than another, determine if pickups that should be alike are in fact alike, or if you buy a new set of pickups, and you want to see how they differ from the old pickups on a technical level, this plot will elucidate that difference. *** You can determine how much of an effect a particular part of a pickup has on it's Q factor and resonant peak. For example, you can plot a humbucker, the remove all the screws, or anything you want, then plot it again, and you will be able to determine the contribution of thsoe component by comparing the difference with and without those parts included. Of if you bought a bunch of pickup arts on eBay and you are unsure of their quality or consistency, this method will reveal any unwanted deviations immediately. Or do as I have recently, measure the difference a steel "base plate" makes on the underside of a Fender pickup, and conclude what I concluded; not much. Generally speaking, when the the resonant frequency decreases, it means the metallic component you have added has increased the inductance of the pickup, due to its having a higher permeability. If the resonant frequency increases, they the opposite is true, so you will find that as you remove slugs, screws, spacers, etc. that the resonant peak frequency increases. Generally speaking, when the resonant peak amplitude decreases in amplitude, which is to say, "the Q factor has dropped" or "the mountain has become a hill", it means the metallic component is imposing eddy current losses, or resistance upon the pickup, meaning the metal is conductive. Higher permeability will also increase the eddy current resistance, but it is only necessary that the metal be conductive. The more conductive and permeable the metal, the greater the eddy current resistance, and the shorter the mountain" will be. This is especially useful for testing the quality of cheap brass versus better nickel silver covers, and figuring out if an eBay seller has screwed you or not. Also note that any kind of series resistance in the circuit, and not just eddy current resistance, will also lower the Q factor. Resistance that is parallel to the pickup also lowers the Q factor, but in that case, a lower resistance lowers the Q factor, and higher resistance increases it. *** You can even perform this test with the pickup still in your guitar, and see the resonant peak and Q factor with the pickup(s) loaded down by the tone and volume posts. You can see how the resonant peak changes when you tweak the knobs on your guitar, or combine pickups. You can compare one guitar to another, one pickup to another, and on and on. Taking things further, you could plug your guitar cable into the guitar, then plot the result from the end of the guitar cable, and witness how much the resonant peak drops on account of the guitar cable, and find out which guitar cables are higher quality than others. I've done some guitar cable testing here using an LCR meter guitarnuts2.proboards.com/thread/7725/capacitive-coupling-various-guitar-partsIn order to better understand the physics involved, it's worth reading up on how core materials effect inductors, by aiding their performance with permeability, and detracting from it through hysteresis and eddy current losses, though only the latter will audibly effect guitar pickups powerelectronics.com/content/inductor-core-material-heart-inductor due to the relatively low frequencies involved. One notable difference is that inductors and often utilize ferrite cores, and transformers utilize steel laminations to achieve a very high Q factor, but as a high Q factor is not generally desirable in a guitar pickup, these techniques are dispensed with. In fact, the parallel circuit resistance of the tone and volume pot lower the Q factor of a pickup, and this is generally considered a good thing. To deliberately retain a higher Q factor, you can use 1 meg or no-load control pots. I'm interested with the Eddy current issues. What tools can we use to directly test metals conductivity and permeability so we can predict if it will result to more Eddy current loss compared to another metal? I'm thinking that this method will be faster and helpful. Or do you have any suggestion to do this? Thanks! |
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Post by antigua on Jan 17, 2020 22:47:18 GMT -5
I'm interested with the Eddy current issues. What tools can we use to directly test metals conductivity and permeability so we can predict if it will result to more Eddy current loss compared to another metal? I'm thinking that this method will be faster and helpful. Or do you have any suggestion to do this? Thanks! There are reference tables online that indicate the permeability and conductivity/resistivity of various metals. Sometimes you have to cobble together numbers from multiple sources, and to make sure they're all in agreement. You can test it on your own, similar to how the eddy currents of pickup covers are tested, or you can measure the DC resistance from one end of the metal to the other, but that would require that all the samples you have on hand be exactly the same dimensions. |
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Post by pablogilberto on Jan 19, 2020 21:25:11 GMT -5
You can test it on your own, similar to how the eddy currents of pickup covers are tested, or you can measure the DC resistance from one end of the metal to the other, but that would require that all the samples you have on hand be exactly the same dimensions. Yes, I also thought about measuring the DC resistance but as you say, its hard since I need all the samples should be exactly the same in terms of dimensions. My goal is to quickly test them before installing/using it as a baseplate material. I'm planning to buy 5 different HB pickups from different manufactures. I'd like to understand the differences in the material that they are using (and its effects). Esp the metal baseplate, metal spacers and steel polepieces. I'm thinking of developing a fast testing strategy that can do this? Hopefully this method will help me understand what difference in materials do the botique (high priced) and low-end priced pickups have. This will also help confirm if OEMs claimed by some manufacturers have the same specs with the original ones. I'm thinking about doing a pickup analysis on a pickup with no metal (like strat) and then, I will place the metal baseplates one at a time near the pickup and then check what happens with the curve. Do you think that this kind of testing will be valid? Thanks! |
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Post by antigua on Jan 21, 2020 0:59:45 GMT -5
You can test it on your own, similar to how the eddy currents of pickup covers are tested, or you can measure the DC resistance from one end of the metal to the other, but that would require that all the samples you have on hand be exactly the same dimensions. Yes, I also thought about measuring the DC resistance but as you say, its hard since I need all the samples should be exactly the same in terms of dimensions. My goal is to quickly test them before installing/using it as a baseplate material. I'm planning to buy 5 different HB pickups from different manufactures. I'd like to understand the differences in the material that they are using (and its effects). Esp the metal baseplate, metal spacers and steel polepieces. I'm thinking of developing a fast testing strategy that can do this? Hopefully this method will help me understand what difference in materials do the botique (high priced) and low-end priced pickups have. This will also help confirm if OEMs claimed by some manufacturers have the same specs with the original ones. I'm thinking about doing a pickup analysis on a pickup with no metal (like strat) and then, I will place the metal baseplates one at a time near the pickup and then check what happens with the curve. Do you think that this kind of testing will be valid? Thanks! The trick is to have a pickup (or two) with known good parts, such as all nickel silver, or AlNiCo of a known grade, and use those as a benchmark for low eddy current losses. Then when you measure new pickups with unknown materials, you can see if they measure a significantly lower Q factor, due to eddy currents. I've tested base plates guitarnuts2.proboards.com/thread/7861/humbucker-base-plates-eddy-currents , and I've tested humbuckers in various states of disassembly in order to figure out which parts of the humbucker cause more or less eddy currents. I've also tested eddy currents in metals by putting them between the active coil and a test pickup guitarnuts2.proboards.com/thread/8444/eddy-currents-orientation-conductive-metal , and you could test eddy currents in different metals the same sort of way, by comparing something that it known to whatever is unknown. I've found that it's enough to test whether a cover is nickel silver or brass, because as you can see with the base plate test, it doesn't really make any difference what metal it is. I've found that the screws and slugs cause most of the eddy current losses, regardless of the cover, but I've found that most all steels used in guitar pickups measure the same guitarnuts2.proboards.com/thread/8036/addiction-steel-alloy-electrical-evaluation . A pickup with steel slugs and screws needs them in order to work properly, and so it is something that can't be changed or really improved much, so it's not worth testing for. I think you will find that pickup quality can mostly be determined by visual inspection. Are the materials good and is it well made? The only two things to measure for electronically are 1) check to see if the cover is brass or nickel silver by checking if the pickup has a high or low Q factor, and 2) checking the inductance of the pickup to make sure it's not too high nor too low, based on your expectations. For example, I see Strat pickups with an inductance of 1 henry, that's too low, or 4 henries, that's too high. It might be possible to detect brass or nickel silver covers with a DE-5000 by comparing the Q factor at 1kHz. I'll give this a try soon and see if I have any luck. If it works, it could save a lot of trouble. |
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Post by pablogilberto on Jan 24, 2020 5:41:00 GMT -5
I have found this very interesting video on Youtube.
Here is the link:
The guy is using the same technique of checking the frequency response of pickups.
He has his own box for doing the testing.
He is only using 1 control knob for Volume and 1 control knob for Tone.
He changes pots values (250k, 500k, 1Meg, etc) and taper (linear and audio) using only switches.
I'd like to get an idea on how can we possibly do this with potentiometers?
I'm thinking about the technique that he did for this to work.
Thank you!
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Post by perfboardpatcher on Jan 26, 2020 6:01:33 GMT -5
He is only using 1 control knob for Volume and 1 control knob for Tone. He changes pots values (250k, 500k, 1Meg, etc) and taper (linear and audio) using only switches. I'd like to get an idea on how can we possibly do this with potentiometers? I'm thinking about the technique that he did for this to work. Thank you! I'm guessing that he is using 4 gang pots on his outboard module. When searching 4 gang potmeters you will find some images on the internet. Something else, it's hard to see on the video clip whether the person bypassed the controls on the guitar itself or not. |
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Post by pablogilberto on Jan 27, 2020 9:22:08 GMT -5
He is only using 1 control knob for Volume and 1 control knob for Tone. He changes pots values (250k, 500k, 1Meg, etc) and taper (linear and audio) using only switches. I'd like to get an idea on how can we possibly do this with potentiometers? I'm thinking about the technique that he did for this to work. Thank you! I'm guessing that he is using 4 gang pots on his outboard module. When searching 4 gang potmeters you will find some images on the internet. Something else, it's hard to see on the video clip whether the person bypassed the controls on the guitar itself or not. Thanks for the input. Assuming he is using a 4 gang pots. Switching from 1Meg, to 500k to 250k to 100k will be easy. The next question is how can we change from Linear to Audio taper? Do you know any trick? Thanks |
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Post by antigua on Jan 27, 2020 17:54:33 GMT -5
I think rather than use a four gang pot, he just used a 1 meg pot, and then put resistors across it to reduce 1 meg to 500k, 250k and 100k. That would be a lot easier than building or acquiring a four gang pot. A 1 meg resistor across a 1 meg pot renders it a 500k pot. 335k parallel resistance takes the 1 meg pot value down to 250k, and 111.5k resistance would give you a 100k pot. The resistors would render the audio tapper to behave more like a linear pot, but for the sake of demonstration it doesn't matter too much.
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Post by pablogilberto on Jan 28, 2020 2:43:10 GMT -5
I think rather than use a four gang pot, he just used a 1 meg pot, and then put resistors across it to reduce 1 meg to 500k, 250k and 100k. That would be a lot easier than building or acquiring a four gang pot. A 1 meg resistor across a 1 meg pot renders it a 500k pot. 335k parallel resistance takes the 1 meg pot value down to 250k, and 111.5k resistance would give you a 100k pot. The resistors would render the audio tapper to behave more like a linear pot, but for the sake of demonstration it doesn't matter too much. , let's say we have 1M pots audio taper and we want to "convert it to linear taper (just what he did in the video), using just 1 switch. With the same control knob. What could be the trick? I'm interested because I want to hear the difference of Audio versus Linear tapers at different positions. Let's say, from 1, 3, 5, 7, 9 and full positions. Thank you! |
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Post by antigua on Jan 28, 2020 11:29:44 GMT -5
I think rather than use a four gang pot, he just used a 1 meg pot, and then put resistors across it to reduce 1 meg to 500k, 250k and 100k. That would be a lot easier than building or acquiring a four gang pot. A 1 meg resistor across a 1 meg pot renders it a 500k pot. 335k parallel resistance takes the 1 meg pot value down to 250k, and 111.5k resistance would give you a 100k pot. The resistors would render the audio tapper to behave more like a linear pot, but for the sake of demonstration it doesn't matter too much. , let's say we have 1M pots audio taper and we want to "convert it to linear taper (just what he did in the video), using just 1 switch. With the same control knob. What could be the trick? I'm interested because I want to hear the difference of Audio versus Linear tapers at different positions. Let's say, from 1, 3, 5, 7, 9 and full positions. Thank you! I dont think there is a way to change a pot from linear to logarithmic, because they have physically different carbon trace strips inside. In that case, I would suspect a dual gang pot was used. |
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Post by perfboardpatcher on Jan 28, 2020 13:59:25 GMT -5
I think rather than use a four gang pot, he just used a 1 meg pot, and then put resistors across it to reduce 1 meg to 500k, 250k and 100k. That would be a lot easier than building or acquiring a four gang pot. A 1 meg resistor across a 1 meg pot renders it a 500k pot. 335k parallel resistance takes the 1 meg pot value down to 250k, and 111.5k resistance would give you a 100k pot. The resistors would render the audio tapper to behave more like a linear pot, but for the sake of demonstration it doesn't matter too much. But then the treble bleed wouldn't give accurate results. At least when the treble bleed does what I think it is doing, shunting the upper leg of the potmeter. |
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Post by antigua on Jan 28, 2020 22:59:07 GMT -5
I think rather than use a four gang pot, he just used a 1 meg pot, and then put resistors across it to reduce 1 meg to 500k, 250k and 100k. That would be a lot easier than building or acquiring a four gang pot. A 1 meg resistor across a 1 meg pot renders it a 500k pot. 335k parallel resistance takes the 1 meg pot value down to 250k, and 111.5k resistance would give you a 100k pot. The resistors would render the audio tapper to behave more like a linear pot, but for the sake of demonstration it doesn't matter too much. But then the treble bleed wouldn't give accurate results. At least when the treble bleed does what I think it is doing, shunting the upper leg of the potmeter. According to this www.geofex.com/article_folders/potsecrets/potscret.htm if resistance is put between the center lug and ground, you get more of a log taper, but if a resistor is put across the center lug and the hot side of the pot, as is the case with a treble bleed, the taper becomes more linear. And if you started out with a linear pot, the taper become reverse log. |
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Post by perfboardpatcher on Jan 29, 2020 14:35:37 GMT -5
But then the treble bleed wouldn't give accurate results. At least when the treble bleed does what I think it is doing, shunting the upper leg of the potmeter. According to this www.geofex.com/article_folders/potsecrets/potscret.htm if resistance is put between the center lug and ground, you get more of a log taper, but if a resistor is put across the center lug and the hot side of the pot, as is the case with a treble bleed, the taper becomes more linear. And if you started out with a linear pot, the taper become reverse log. Antigua, I was referring to the treble bleed section in the left upper corner on the guy's console. For me it's the most likely that the values 100k, 250k, 500k and 1M refer to the resistance of the volume potmeter. About the controls. Are they perhaps rotary switches? In the Mouser catalog they go up to 12 decks. |
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Post by pablogilberto on Feb 2, 2020 20:50:02 GMT -5
I'm thinking of Measuring the Electrical Properties of guitar effects pedal.
Primarily the analog ones. Let's say an overdrive.
Is it possible to use a similar technique like what we are doing here?
Sending a frequency sweep signal from 0Hz to 20Khz on the input side and then getting the output.
This way, we can compare the freq response.
Do you think that this approach will work?
I know that this can be hard since the freq response will surely change a lot everytime we turn any knob from the pedal controls (drive, tone, gain, EQ, etc)
Or do you have other suggestions or is it entirely different approach?
I also want to investigate those things.
Will appreciate if you can share your experience or point me to any reliable source about this.
Thank you!
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Post by wgen on Feb 3, 2020 8:28:45 GMT -5
Just my two cents here. I've been trying to analyze the behavior and frequency response of all my gear from some time until now.
My setup has been like this : signal generator app in my smartphone, with which I'd send a white noise via minijack to a Digitech loop station Solo Xt model. This one has a minijack input, I use this only to avoid adapters and trying to avoid impedance mismatches, since the Digitech pedal should have the minijack input just for this reasons.
Then, from the normal output mono jack of the Digitech pedal I enter into the input of what I want to analyze.
From the output mono of the pedal/line out of amplifier heads and combos I then enter your typical DAW and computer. With a standard Cubase in my case. In the insert of the audio track I'm recording I put a Frequency Analyzer tool. Or, you can use the Analyzer directly inside Cubase if you are using this.
I'd say this isn't very much ideal : the frequency response will vary depending on the settings of your drive /gain potentiometer, if you are using an overdrive or distortion pedal, or an amp head which is clipping. The higher the gain, the bassier the response.
I guess this is especially due to the white noise having a full bandwidth. The clipping of the bassier frequencies of the white noise generates intermodulation harmonics and bass content which wouldn't be had if using a guitar.
The best is using directly your guitar with this setup and maybe compare the response with other guitars you have
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Post by antigua on Feb 3, 2020 21:45:44 GMT -5
I'm thinking of Measuring the Electrical Properties of guitar effects pedal. Primarily the analog ones. Let's say an overdrive. Is it possible to use a similar technique like what we are doing here? Sending a frequency sweep signal from 0Hz to 20Khz on the input side and then getting the output. This way, we can compare the freq response. Do you think that this approach will work? I know that this can be hard since the freq response will surely change a lot everytime we turn any knob from the pedal controls (drive, tone, gain, EQ, etc) Or do you have other suggestions or is it entirely different approach? I also want to investigate those things. Will appreciate if you can share your experience or point me to any reliable source about this. Thank you! Bode plotters are used for this purpose probably more than anything. Stratotarts uses the Rightmark Audio Analyzer to scan pickups, but it's most common applications, AFAIK, is determining how flat the response is of an audio setup. You can either hook up the soundcard or Velleman directly to the ins and outs of the equipment, or have the equipment output a signal through the speakers, and measure the input with a microphone and sound board in order to plot the response curve of a speaker. Most guitar pedals and amps are not flat, because they want to deliberately emphasize some frequencies more than others. The Rightmark software paired with a sound card or the Velleman bode plotter can plot the EQ profile of guitar amps and pedal. I think mostly what you find is that they attenuate high and low end to varying degrees, in order to keep the overdriven signal sounding smooth in the treble end and tight in the bass end. Probably the most interesting thing to do is map out what the tone controls do to the frequency response on various amps and pedals. Like pickups, specs of this sort are almost never provided by pedal or amp makers, and it would be nice to know, for example, how the tone control of a Klon compares to a Tube Screamer without having to really on "feel" all the time. There are aspects of overdrive pedals it won't reveal though, such as clipping characteristics. To get that, you'd want to input a sine wave, run the pedal into overdrive, and observe whether the pedal delivers hard (sharp squares) or soft clipping (rounded off squares). You can also input square waves into the pedal and observe slew rates, if there is one. Much of this is audible, if you know what to listen for, so this basically just lets you see what you're hearing. There might be a way to quantify these things thew way we quantify pickup specs, to assign some value to the clipping characteristic or the slew rate, but I'm not familiar with doing that sort of documentation. |
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Post by straylight on Feb 3, 2020 23:08:14 GMT -5
Analysing overdrives gets complicated. You can throw a sine wave in and look at the wave shape that comes out, look at the frequency response and how the tone stack alters the response, and that's fairly simple if a lot of bode plots. Then you start varying the drive level and input level and the shape of frequency response changes immensely. I think it's something you'd need to plot as a 3d surface (working on it) and automate a series of sweeps at different input levels (working on it) in order to get some kind of meaningful analysis. And I'm not sure how you'd go about plotting transient response. Where i have seen analysis of pedals, it's been a wave plot and response plot of an arbitrary signal through each functional unit of the pedal rather than just lobbing it on the bench and running the bode plotter on the 'scope.
A starting point to consider for analysis is screamer and boss SD-1 type pedals have a big midrange hump at low gain but the frequency response flattns out as you crank the drive and the mids get more distorted. A Klon clone (soul food and cheapy pedals) is super-flat at low gain and humps more as you crank the gain up. Full on distortions like the DS-1 and bigmuff have the same scooped response no matter how gently or hard you drive them.
If you are ok stacking CSV plots in excel or plotting otherwise i can make what I have available? Otherwise I can try to get some rudimentarty R example code to read and stack arbitrary plots?
I'm not sure any meaningful measurments can be made from what I have though, it's more a shape and behaviour thing i cobbled togetehr in an afternoon to explain the difference between a few kinds of pedals.
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Post by pablogilberto on Feb 4, 2020 22:03:56 GMT -5
Just my two cents here. I've been trying to analyze the behavior and frequency response of all my gear from some time until now. My setup has been like this : signal generator app in my smartphone, with which I'd send a white noise via minijack to a Digitech loop station Solo Xt model. This one has a minijack input, I use this only to avoid adapters and trying to avoid impedance mismatches, since the Digitech pedal should have the minijack input just for this reasons. Then, from the normal output mono jack of the Digitech pedal I enter into the input of what I want to analyze. From the output mono of the pedal/line out of amplifier heads and combos I then enter your typical DAW and computer. With a standard Cubase in my case. In the insert of the audio track I'm recording I put a Frequency Analyzer tool. Or, you can use the Analyzer directly inside Cubase if you are using this. I'd say this isn't very much ideal : the frequency response will vary depending on the settings of your drive /gain potentiometer, if you are using an overdrive or distortion pedal, or an amp head which is clipping. The higher the gain, the bassier the response. I guess this is especially due to the white noise having a full bandwidth. The clipping of the bassier frequencies of the white noise generates intermodulation harmonics and bass content which wouldn't be had if using a guitar. The best is using directly your guitar with this setup and maybe compare the response with other guitars you have Thanks for sharing this! |
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Post by pablogilberto on Feb 4, 2020 22:05:41 GMT -5
Bode plotters are used for this purpose probably more than anything. Stratotarts uses the Rightmark Audio Analyzer to scan pickups, but it's most common applications, AFAIK, is determining how flat the response is of an audio setup. You can either hook up the soundcard or Velleman directly to the ins and outs of the equipment, or have the equipment output a signal through the speakers, and measure the input with a microphone and sound board in order to plot the response curve of a speaker. Most guitar pedals and amps are not flat, because they want to deliberately emphasize some frequencies more than others. The Rightmark software paired with a sound card or the Velleman bode plotter can plot the EQ profile of guitar amps and pedal. I think mostly what you find is that they attenuate high and low end to varying degrees, in order to keep the overdriven signal sounding smooth in the treble end and tight in the bass end. Probably the most interesting thing to do is map out what the tone controls do to the frequency response on various amps and pedals. Like pickups, specs of this sort are almost never provided by pedal or amp makers, and it would be nice to know, for example, how the tone control of a Klon compares to a Tube Screamer without having to really on "feel" all the time. There are aspects of overdrive pedals it won't reveal though, such as clipping characteristics. To get that, you'd want to input a sine wave, run the pedal into overdrive, and observe whether the pedal delivers hard (sharp squares) or soft clipping (rounded off squares). You can also input square waves into the pedal and observe slew rates, if there is one. Much of this is audible, if you know what to listen for, so this basically just lets you see what you're hearing. There might be a way to quantify these things thew way we quantify pickup specs, to assign some value to the clipping characteristic or the slew rate, but I'm not familiar with doing that sort of documentation. Thanks for the idea. I will consider this. |
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Post by pablogilberto on Feb 4, 2020 22:12:22 GMT -5
Analysing overdrives gets complicated. You can throw a sine wave in and look at the wave shape that comes out, look at the frequency response and how the tone stack alters the response, and that's fairly simple if a lot of bode plots. Then you start varying the drive level and input level and the shape of frequency response changes immensely. I think it's something you'd need to plot as a 3d surface (working on it) and automate a series of sweeps at different input levels (working on it) in order to get some kind of meaningful analysis. And I'm not sure how you'd go about plotting transient response. Where i have seen analysis of pedals, it's been a wave plot and response plot of an arbitrary signal through each functional unit of the pedal rather than just lobbing it on the bench and running the bode plotter on the 'scope.
A starting point to consider for analysis is screamer and boss SD-1 type pedals have a big midrange hump at low gain but the frequency response flattns out as you crank the drive and the mids get more distorted. A Klon clone (soul food and cheapy pedals) is super-flat at low gain and humps more as you crank the gain up. Full on distortions like the DS-1 and bigmuff have the same scooped response no matter how gently or hard you drive them. If you are ok stacking CSV plots in excel or plotting otherwise i can make what I have available? Otherwise I can try to get some rudimentarty R example code to read and stack arbitrary plots?
I'm not sure any meaningful measurments can be made from what I have though, it's more a shape and behaviour thing i cobbled togetehr in an afternoon to explain the difference between a few kinds of pedals.
Thanks for your inputs. I have some follow-up questions. 1. "You can throw a sine wave in and look at the wave shape that comes out, look at the frequency response and how the tone stack alters the response, and that's fairly simple if a lot of bode plots. " - What kind of sinewave generator do you use for this? What is the standard/ideal amplitude and frequency value for this test signal? 2. "Where i have seen analysis of pedals, it's been a wave plot and response plot of an arbitrary signal through each functional unit of the pedal rather than just lobbing it on the bench and running the bode plotter on the 'scope." - What do you exactly mean by this? Do you mean that they usually open the circuit board and choose particular test points? Can you share to me where can I read about experimentations/testing like this? 3. "A starting point to consider for analysis is screamer and boss SD-1 type pedals have a big midrange hump at low gain but the frequency response flattns out as you crank the drive and the mids get more distorted. A Klon clone (soul food and cheapy pedals) is super-flat at low gain and humps more as you crank the gain up. Full on distortions like the DS-1 and bigmuff have the same scooped response no matter how gently or hard you drive them." - Thanks for this valuable info. Can you share your experiment setup so I can try it too? 4. "If you are ok stacking CSV plots in excel or plotting otherwise i can make what I have available? Otherwise I can try to get some rudimentarty R example code to read and stack arbitrary plots?" - Yes please share whatever you have so I'll have more idea about it. Thank you so much! |
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Post by JohnH on Feb 5, 2020 0:27:53 GMT -5
I would suggest that to study the response of overdrive pedals, in cases of a known design such as TS, Sd1 or Marshall, more insight can be obtained more easily through building a Spice model. Thus can give you bode-like plots of both small signal gain and overdrive or transient response. I've found this very useful for figuring out mods etc, If wanted I can post results into a new thread in the effects section.
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Post by antigua on Feb 5, 2020 18:07:29 GMT -5
Analysing overdrives gets complicated. You can throw a sine wave in and look at the wave shape that comes out, look at the frequency response and how the tone stack alters the response, and that's fairly simple if a lot of bode plots. Then you start varying the drive level and input level and the shape of frequency response changes immensely. I think it's something you'd need to plot as a 3d surface (working on it) and automate a series of sweeps at different input levels (working on it) in order to get some kind of meaningful analysis. And I'm not sure how you'd go about plotting transient response. Where i have seen analysis of pedals, it's been a wave plot and response plot of an arbitrary signal through each functional unit of the pedal rather than just lobbing it on the bench and running the bode plotter on the 'scope.
A starting point to consider for analysis is screamer and boss SD-1 type pedals have a big midrange hump at low gain but the frequency response flattns out as you crank the drive and the mids get more distorted. A Klon clone (soul food and cheapy pedals) is super-flat at low gain and humps more as you crank the gain up. Full on distortions like the DS-1 and bigmuff have the same scooped response no matter how gently or hard you drive them. If you are ok stacking CSV plots in excel or plotting otherwise i can make what I have available? Otherwise I can try to get some rudimentarty R example code to read and stack arbitrary plots?
I'm not sure any meaningful measurments can be made from what I have though, it's more a shape and behaviour thing i cobbled togetehr in an afternoon to explain the difference between a few kinds of pedals.
Thanks for your inputs. I have some follow-up questions. 1. "You can throw a sine wave in and look at the wave shape that comes out, look at the frequency response and how the tone stack alters the response, and that's fairly simple if a lot of bode plots. " - What kind of sinewave generator do you use for this? What is the standard/ideal amplitude and frequency value for this test signal? 2. "Where i have seen analysis of pedals, it's been a wave plot and response plot of an arbitrary signal through each functional unit of the pedal rather than just lobbing it on the bench and running the bode plotter on the 'scope." - What do you exactly mean by this? Do you mean that they usually open the circuit board and choose particular test points? Can you share to me where can I read about experimentations/testing like this? 3. "A starting point to consider for analysis is screamer and boss SD-1 type pedals have a big midrange hump at low gain but the frequency response flattns out as you crank the drive and the mids get more distorted. A Klon clone (soul food and cheapy pedals) is super-flat at low gain and humps more as you crank the gain up. Full on distortions like the DS-1 and bigmuff have the same scooped response no matter how gently or hard you drive them." - Thanks for this valuable info. Can you share your experiment setup so I can try it too? 4. "If you are ok stacking CSV plots in excel or plotting otherwise i can make what I have available? Otherwise I can try to get some rudimentarty R example code to read and stack arbitrary plots?" - Yes please share whatever you have so I'll have more idea about it. Thank you so much! The Vellaman PCSU200 has a built in function generator that creates sine waves and all sorts of others. The Rightmark software will turn the headphone output of a sound card into a function generator, but I haven't used it that much. A USB oscilloscope like the PSCU200 is easier to use because it's software and hardware that is intended for this sort of purpose. The Velleman bode plotter supports numerous overlapping plots, so you can do what I did with a Marshall head, and run a sweep, then change a knob setting on the amp and then sweep it again, and you can see how the response changes as you tweak a given knob.  For the slew rate or clipping analysis, you'd not use a bode plot, you would use the oscilloscope mode. As per this site, you would see variance in hot the pedal reshapes the sine wave www.generalguitargadgets.com/how-to-build-it/technical-help/articles/design-distortion/  Here's someone who used a hardware oscilloscope lifestyle.jimdunlop.com/the-dunlop-distortion-guide/ . In the pic you can see the function generator sitting on top of the oscilloscope. The Velleman PCSU200 is both of those pieces of equipment in one box and only costs $120.    |
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Post by pablogilberto on Feb 7, 2020 1:45:52 GMT -5
I would suggest that to study the response of overdrive pedals, in cases of a known design such as TS, Sd1 or Marshall, more insight can be obtained more easily through building a Spice model. Thus can give you bode-like plots of both small signal gain and overdrive or transient response. I've found this very useful for figuring out mods etc, If wanted I can post results into a new thread in the effects section. Yes, I would love to see experiment setup and results so I can try them too. " in cases of a known design such as TS, Sd1 or Marshall" -Will also appreciate if you can share your reference schematics of this pedals. Thanks! |
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Post by pablogilberto on Feb 7, 2020 1:47:54 GMT -5
Thanks for your inputs. I have some follow-up questions. 1. "You can throw a sine wave in and look at the wave shape that comes out, look at the frequency response and how the tone stack alters the response, and that's fairly simple if a lot of bode plots. " - What kind of sinewave generator do you use for this? What is the standard/ideal amplitude and frequency value for this test signal? 2. "Where i have seen analysis of pedals, it's been a wave plot and response plot of an arbitrary signal through each functional unit of the pedal rather than just lobbing it on the bench and running the bode plotter on the 'scope." - What do you exactly mean by this? Do you mean that they usually open the circuit board and choose particular test points? Can you share to me where can I read about experimentations/testing like this? 3. "A starting point to consider for analysis is screamer and boss SD-1 type pedals have a big midrange hump at low gain but the frequency response flattns out as you crank the drive and the mids get more distorted. A Klon clone (soul food and cheapy pedals) is super-flat at low gain and humps more as you crank the gain up. Full on distortions like the DS-1 and bigmuff have the same scooped response no matter how gently or hard you drive them." - Thanks for this valuable info. Can you share your experiment setup so I can try it too? 4. "If you are ok stacking CSV plots in excel or plotting otherwise i can make what I have available? Otherwise I can try to get some rudimentarty R example code to read and stack arbitrary plots?" - Yes please share whatever you have so I'll have more idea about it. Thank you so much! The Vellaman PCSU200 has a built in function generator that creates sine waves and all sorts of others. The Rightmark software will turn the headphone output of a sound card into a function generator, but I haven't used it that much. A USB oscilloscope like the PSCU200 is easier to use because it's software and hardware that is intended for this sort of purpose. The Velleman bode plotter supports numerous overlapping plots, so you can do what I did with a Marshall head, and run a sweep, then change a knob setting on the amp and then sweep it again, and you can see how the response changes as you tweak a given knob. For the slew rate or clipping analysis, you'd not use a bode plot, you would use the oscilloscope mode. As per this site, you would see variance in hot the pedal reshapes the sine wave www.generalguitargadgets.com/how-to-build-it/technical-help/articles/design-distortion/ Here's someone who used a hardware oscilloscope lifestyle.jimdunlop.com/the-dunlop-distortion-guide/ . In the pic you can see the function generator sitting on top of the oscilloscope. The Velleman PCSU200 is both of those pieces of equipment in one box and only costs $120. This is so cool and informative! Thank you! |
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Post by pablogilberto on Feb 7, 2020 1:50:18 GMT -5
I have seen this strat pickup with copper taper shielding below the fiber plate.  o captain my captain movieDO you have any experience about this? Will this be a good shielding practice? I think this will make the polepieces connected to the ground. Will it introduce Eddy Currents that might affect the tone? thanks! |
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Post by stratotarts on Feb 7, 2020 15:12:04 GMT -5
I have seen this strat pickup with copper taper shielding below the fiber plate. DO you have any experience about this? Will this be a good shielding practice? I think this will make the polepieces connected to the ground. Will it introduce Eddy Currents that might affect the tone? thanks! I haven't seen it on a Strat before. It seems like a good idea. It will not introduce significant eddy currents because it is distant from the string field, and not relatively very conductive because of the thin-ness of the copper tape. Even when a coil is wrapped externally with copper tape, the losses are not huge (although in that case, they may be considered significant, e.g. a few dB). |
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Post by antigua on Feb 8, 2020 1:24:16 GMT -5
I have seen this strat pickup with copper taper shielding below the fiber plate. o captain my captain movieDO you have any experience about this? Will this be a good shielding practice? I think this will make the polepieces connected to the ground. Will it introduce Eddy Currents that might affect the tone? thanks! In theory grounding the pole pieces can potentially make the pickup quieter, if the "start" of the coil is on the inside. Humbuckers and P-90's have grounded steel pole pieces. The lower permeability and conductivity of AlNiCo must make them less effective noise antennas than steel screws and slugs, though. This would increase the capacitance by some small amount also. Overall I don't think it matters much, just as a Tele base plate doesn't matter much. It would be easy to test with a piece of tiny foil and test leads. |
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