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Post by Charlie Honkmeister on Apr 10, 2017 12:39:17 GMT -5
Nice work on the coil, Antigua.
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Post by antigua on Apr 15, 2017 12:05:09 GMT -5
Just an update; I've been looking into 3d spectrographing software, and haven't found any free solution that looks like it's especially usable. Some professional grade versions cost up $500 to $1000, which is more than I want to spend, so I have to find something in between, and it's slow going.
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Post by wgen on Apr 22, 2017 4:55:24 GMT -5
I'm writing here because I'd like to talk about something that has already been discussed here and there in the past, but I'd like to better understand this subject, if you elaborated it some. I thought that it could have affinities with the subject of this thread. I was thinking about different string gauges/string tension, and the different tonal response your pickups have in relation to this. A thinner, lower tension, let's say a round core instead of hex core, very flexible string, would translate into a bigger movement at the transients, which in my understanding, and should I say, to my ear too, seems to increase the "attack", the higher treble peak the pickup can have as you pluck your strings. But, soon after the transient, the sound seems to get even more bottom end than higher tension strings, though, more focus in the fundamental. Higher tension strings seem to have a more "dull" attack, but more "punch" overall, kind of like they have a focus on higher harmonics in respect to the fundamental, but still in the lower midrange range of frequencies, definitely not in the resonant peak frequency range of typical pickups. I think that, for some reasons, I can hear more of these differences in string gauges playing the bass. This subject would be somewhat confirmed from Antigua's analysis, where harmonics focus sampled by the pickups seems to be concentrated mostly in lower order harmonics, which, unless you are playing lines over the 12th fret, translate into lower midrange frequencies area, under 1000 Hz, more or less. In fact, it seems to me that, when you have a focus in harmonics sampling from the pickups, it always seems to happen the most in the range of lower order harmonics. What do you think about this?
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Post by antigua on Apr 22, 2017 23:24:34 GMT -5
I'm writing here because I'd like to talk about something that has already been discussed here and there in the past, but I'd like to better understand this subject, if you elaborated it some. I thought that it could have affinities with the subject of this thread. I was thinking about different string gauges/string tension, and the different tonal response your pickups have in relation to this. A thinner, lower tension, let's say a round core instead of hex core, very flexible string, would translate into a bigger movement at the transients, which in my understanding, and should I say, to my ear too, seems to increase the "attack", the higher treble peak the pickup can have as you pluck your strings. But, soon after the transient, the sound seems to get even more bottom end than higher tension strings, though, more focus in the fundamental. Higher tension strings seem to have a more "dull" attack, but more "punch" overall, kind of like they have a focus on higher harmonics in respect to the fundamental, but still in the lower midrange range of frequencies, definitely not in the resonant peak frequency range of typical pickups. I think that, for some reasons, I can hear more of these differences in string gauges playing the bass. This subject would be somewhat confirmed from Antigua's analysis, where harmonics focus sampled by the pickups seems to be concentrated mostly in lower order harmonics, which, unless you are playing lines over the 12th fret, translate into lower midrange frequencies area, under 1000 Hz, more or less. In fact, it seems to me that, when you have a focus in harmonics sampling from the pickups, it always seems to happen the most in the range of lower order harmonics. What do you think about this? I think you're referring to the effects of string stiffness. It's actually easy(ish) to find info about this subject with Google searches, because it's not specific to electric guitars, but applies to acoustic stringed instruments in general, of which there has been a lot written, relative to issues specific to guitar pickups. The higher harmonics represent shorter segments of string deformation. A string bends more easily over a longer distance than a shorter one, so those short, higher pitched harmonics get damped out quickly compared to the wider, lower harmonics, that bend the string over a wider length. This is true of most all stringed instruments (when you're not using bow), so there's a lot of information out there. How magnetic guitar pickups make the matter more interesting is in how they attenuate a lot of the higher harmonics, especially in the transient. If an electric guitar has a pickup with a high resonant peak, it will sound like it has a sharp, glassy attack, like an acoustic guitar, or a mandolin, or a sitar, but if the pickup has a low resonant peak, it rolls off the high harmonics, making the attack almost more like a nylon stringed guitar. I think that's one thing (among many) a lot of people don't realize about pickups, is that the frequency response dictates the "attack", as well as the overall perception of treble.
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Post by antigua on Apr 23, 2017 0:21:14 GMT -5
I did find something kind of interesting with 2D spectrograms, and adjusting the pickup heights. There wasn't much of a difference when plucking one string, but there were some differences with phase cancellations when playing a full chord. The reason for this is that when you pluck a single string, there are no overlapping harmonics, but when you play a chord, a lot of the harmonics from the different strings overlap, and are not perfect in phase with each other. It appears that there was some differences in the phase cancellation interval with the changing of the pickup height (or the resulting variation in magnetic pull). I thought those 3D spectrograms might be helpful, but it looks like it might be easier to discover something with the simple 2D type. The 3D spectrogram is essentially the same thing, but with "height" in place of brightness. Here is a strummed open E chord, four strums, each 6 seconds in duration, bridge pickup close, neck pickup close, bridge pickup far, neck pickup far. (bridge close, neck close, bridge far, neck far): Here is the same as above, but now I've amplified the "far pickup" side to the right to be roughly equal in overall amplitude to the the "near pickup" left: (bridge close, neck close, bridge far, neck far) If you look at the 3rd, 5th and 7th band of harmonic overlaps, and the you can see that the phasing of the overlapping signals caused more rapid pulsing when the pickup is farther from the strings, and less rapid when the pickup was closer. The pulsating is audible, especially in isolation. If I open up 30 band EQ and cut everything aside from specific harmonics, like say 250Hz or 500Hz, I can hear that harmonic pulsate in loudness as appears in the spectrogram. Here is a plucked A string, with the "far" amplitude increased to match the "near" amplitude: (bridge close, neck close, bridge far, neck far) You can see that a single plucked string doesn't appear to pulse much by itself, regardless of pickup height or pickup position. There is a little bit of pulsing in the higher harmonics, but in this case it's caused by the transfer of energy to different harmonics levels as the string movement decays, and not phase cancellation with another string. Here is a demonstration of the harmonic phase cancellations with the high E string, and the the high E and the B string fretted at the 5th fret, using the neck pickup set low. It can be seen that the harmonics all pulse at different intervals, getting smaller with the increasing harmonic: I think the thing to investigate next is whether or not different chords might bring out bigger phase differences depending on pickup height, and the magnetic pull that results.
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Post by antigua on Apr 23, 2017 16:24:31 GMT -5
This appears to have turned up nothing. I did eight E chord strums, four width the bridge pickup close, and four with the pickup far away from the strings, and I don't really see any patterns. Variations in the phase pulsing seem to be a fluke, probably having to due with slight variations in string tuning (or pressing down on the strings with more force). This is very frustrating, because it's always seemed to me (and a lot of other guitarists) that the tone changes with pickup height. I have to admit though, I don't hear much difference in the actual recordings, I mostly perceive a difference when I'm actually plugged into an amp, which gets me to thinking that this might have more to do with increasing voltage in front of amp, than anything relating to the pickups, so that might be where I look next for variation by pickup height. If the difference owes to "push", though, I should be able to duplicate any such difference with a booster.
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Post by stratotarts on Apr 24, 2017 10:08:29 GMT -5
This is very frustrating, because it's always seemed to me (and a lot of other guitarists) that the tone changes with pickup height. I have to admit though, I don't hear much difference in the actual recordings, I mostly perceive a difference when I'm actually plugged into an amp, which gets me to thinking that this might have more to do with increasing voltage in front of amp, than anything relating to the pickups, so that might be where I look next for variation by pickup height. If the difference owes to "push", though, I should be able to duplicate any such difference with a booster. I performed a crude version of this experiment and posted on TDPRI a while back. I also didn't see much, or hear any difference. Basically I recorded samples and adjusted the volume to make them equal. Of course, an experiment with limitations produces accordingly limited results. But I think that you can at least say, the effects must be much more subtle than is commonly believed, because statements like "night and day difference" are often used. Sometimes people imply that it makes more difference than anything else. Since the effects of those "anything else" have been found to be clearly and easily measurable, the expectation that this aspect would also be obvious if it were that obvious seems reasonable. I think you are on the right track with the amplifier theory. The other thing that people might change when the pickup changes, is the guitar volume knob. We know that it makes a difference. I also think there must be some difference. So a refinement of the experiment could reveal the actual extent. To quantify it would help a lot to put the doubts to rest. I wish I had the time for it now.
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Post by ms on Apr 24, 2017 10:32:05 GMT -5
This appears to have turned up nothing. A pickup with strong magnets has an obvious effect when placed close to the strings, and therefore, you expect more subtle effects at greater distances. But what could these effects be, and how significant are they? Consider a string. In addition to having mass and elasticity, it has stiffness. This stiffness causes the higher harmonics to shift in frequency, no longer exact multiples of the fundamental. You can measure this using a system with enough frequency resolution and dynamic range. You can even show that harmonics caused by distortion of the fundamental and lower harmonics are not at the same frequency as the string harmonics. I think if you make a system that can detect these effects, then you have greater chance of seeing effects from changing the pickup height, which might well take the form of subtle shifts in the frequencies of the higher harmonics. I think you will not see much until you get very close to where audible "stratitis" sets in.
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Post by antigua on Apr 24, 2017 11:26:55 GMT -5
This appears to have turned up nothing. A pickup with strong magnets has an obvious effect when placed close to the strings, and therefore, you expect more subtle effects at greater distances. But what could these effects be, and how significant are they? Consider a string. In addition to having mass and elasticity, it has stiffness. This stiffness causes the higher harmonics to shift in frequency, no longer exact multiples of the fundamental. You can measure this using a system with enough frequency resolution and dynamic range. You can even show that harmonics caused by distortion of the fundamental and lower harmonics are not at the same frequency as the string harmonics. I think if you make a system that can detect these effects, then you have greater chance of seeing effects from changing the pickup height, which might well take the form of subtle shifts in the frequencies of the higher harmonics. I think you will not see much until you get very close to where audible "stratitis" sets in. I still have that coil ready to go for testing magnetic pull in a steady state, but I did this strumming thing this time because my feeling is that I can hear the difference when strumming, so I should see a difference if I just strummed the strings. I'll go back to the steady state testing again soon to see if the magnetic exciter shows the same results as vibrating the head stock.
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Post by antigua on Apr 24, 2017 11:33:58 GMT -5
I have a question, does the frequency response of an amplifier vary with input voltage? This is another way of asking whether amp has a linear transfer function, and I know they are generally not perfectly linear, but I haven't seen a lot of discussion about this specific subject, as far as how it impacts a guitarist's life. I need to figure out how to best test the transfer function of the amp. I can use a microphone and an amp, but the setup for this test is kind of difficult and will add the curves of the microphone and speaker into the equation, so I'm wondering if I can use the guitar input "in" and effects loop "out" to just test the linearity of the amp's input stage, and ignore the power stage. Based on this test guitarnuts2.proboards.com/post/80880/thread it looks like a Strat type single coil stays under 500mV, but humbuckers easily kick up to several volts on the transient, which I figure hits the dynamic limit of a 9V powered travel amp, but I'm not sure what happens with a full powered amp. If for example, it turns out that higher and lower frequencies are magnified relative to mid range frequencies, I'd expect a pickup to sound more "scooped" by virtue of its hitting the amp with a higher voltage. Lowering the pickup could therefore reduce the highs and lows by reducing the input voltage. If this is the case, should the same effect be expected from a linear volume booster pedal, or could the change in input impedance (from high Z guitar to low Z volume boost pedal) cause the amp's transfer function to be different?
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Post by ms on Apr 24, 2017 14:22:04 GMT -5
I have a question, does the frequency response of an amplifier vary with input voltage? This is another way of asking whether amp has a linear transfer function, and I know they are generally not perfectly linear, but I haven't seen a lot of discussion about this specific subject, as far as how it impacts a guitarist's life. I need to figure out how to best test the transfer function of the amp. I can use a microphone and an amp, but the setup for this test is kind of difficult and will add the curves of the microphone and speaker into the equation, so I'm wondering if I can use the guitar input "in" and effects loop "out" to just test the linearity of the amp's input stage, and ignore the power stage. Based on this test guitarnuts2.proboards.com/post/80880/thread it looks like a Strat type single coil stays under 500mV, but humbuckers easily kick up to several volts on the transient, which I figure hits the dynamic limit of a 9V powered travel amp, but I'm not sure what happens with a full powered amp. If for example, it turns out that higher and lower frequencies are magnified relative to mid range frequencies, I'd expect a pickup to sound more "scooped" by virtue of its hitting the amp with a higher voltage. Lowering the pickup could therefore reduce the highs and lows by reducing the input voltage. If this is the case, should the same effect be expected from a linear volume booster pedal, or could the change in input impedance (from high Z guitar to low Z volume boost pedal) cause the amp's transfer function to be different? Yes, you can use the guitar input and effects out. Use a sine wave and measure the spectrum and look at the level of he harmonics. You can also probably find software that plots this as a transfer function which becomes flat as you approach clipping. Non linearity produces harmonics and intermodulation. This is certainly audible! As you turn an amp up even into clipping you might hear more bass, but that is likely just Fletcher Munson (changes in the sensitivity of the ear-brain as the sound level into the ear is increased).
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Post by stratotarts on Apr 25, 2017 8:33:07 GMT -5
I have a question, does the frequency response of an amplifier vary with input voltage? Sort of. Due to slew rate limiting, the maximum signal amplitude decreases with increasing frequency. Because the useful area of operation of most amps is the linear region, this can be expressed as GBW (gain-bandwidth product). But real world amps like a guitar amp are designed so that the gain is adequate for the highest frequency. In that case, the maximum input level does not depend on frequency. Also within the specified operating limits, the input-output differential (gain) mainly does not depend on frequency unless there is equalization (such as tone circuitry). There will be some non-linearity in both the time and frequency domain due to the imperfections of real world components and circuits.
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Post by antigua on Apr 25, 2017 10:04:50 GMT -5
Here is test I did with a Marshall JVM410c, a fairly beefy tube amp. I still have one or two more amps I can test out. This is what happens when the bode plotter's input is into the front of the amp, and the difference is measured at the effects loop out, which the signal generator's voltage stepped up by 100mV increments. And here was what happened when I fixed the input at 200mV and turned up the volume knob on the pre-amp of the amp: I have to do this second one again, because as the tubes were powered on longer and became hotter, I think the treble emphasis towards 10kHz increasingly diminished, as you can see with the higher voltages (I went low to high). I'll leave the amp on for an hour, and then give it another go. I don't yet know a whole lot about how amplifiers work, but these transfer functions look far from flat. On the input side, it looks for a given increase in voltage, you get a greater than 1:1 ratio above 500Hz, increasingly so with frequency and voltage.
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Post by ms on Apr 25, 2017 13:18:58 GMT -5
Here is test I did with a Marshall JVM410c, a fairly beefy tube amp. I still have one or two more amps I can test out. I think it would be a lot easier to see changes in frequency response with level changes if you plotted in db.
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Post by JohnH on Apr 25, 2017 15:28:41 GMT -5
That JVM is a magnificent amp!
I think that as an amp is turned up in volume, all frequency responses should stay in balance (db bode plots look like a series of parallel curves), except for two things:
1. Many amps have a treble bleed cap on the volume pot, that adds treble at lower volumes. 2. Once harmonic distortion is getting up into musically significant levels, all bets are off, higher harmonics of lower input frequencies are increasingly being created in the amp.
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Post by antigua on Apr 25, 2017 17:26:24 GMT -5
Here is test I did with a Marshall JVM410c, a fairly beefy tube amp. I still have one or two more amps I can test out. I think it would be a lot easier to see changes in frequency response with level changes if you plotted in db. If the amplification is linear, shouldn't a linear scale show fairly straight lines?
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Post by ms on Apr 26, 2017 10:06:38 GMT -5
I think it would be a lot easier to see changes in frequency response with level changes if you plotted in db. If the amplification is linear, shouldn't a linear scale show fairly straight lines? Let's assume we have a guitar amp with such an input level and adjustments of the gain and master volume controls so that there is no clipping. Even if you have the tone control adjusted all on 5, the frequency response is not flat, but rather shows emphasis in the upper midrange and low highs. If you want to show that the frequency response changes when you turn up the input level, maybe because you are driving at least one stage nonlinear, then you need to be able to compare the changes at different frequencies. The only was to put them onto equal footing is to use a log scale, and a db realization of that is the usual audio practice.
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Post by antigua on Apr 26, 2017 12:38:52 GMT -5
Here is the bode plot of the Velleman bode plotter's output wire to the output, in 600mV VRMS steps to match their grid overlay. I'm not sure why it attenuates with frequency, maybe due to capacitance, but it appears to become stronger with voltage. I don't know if this is normal, or a sign that this is defective or would require some sort of calibration. Here's the Marshall JVM plots in logarithmic and linear: logarithmic linear The log plot does look more proportional, though still not linear, but the input steps are in 100mV Vpp linear increments, so it appears to me that it's the amp that has a logarithmic treble boost with respect to input voltage, unless I'm reading this wrong.
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Post by ms on Apr 26, 2017 14:09:56 GMT -5
Here is the bode plot of the Velleman bode plotter's output wire to the output, in 600mV VRMS steps to match their grid overlay. I'm not sure why it attenuates with frequency, maybe due to capacitance, but it appears to become stronger with voltage. I don't know if this is normal, or a sign that this is defective or would require some sort of calibration. The log plot does look more proportional, though still not linear, but the input steps are in 100mV Vpp linear increments, so it appears to me that it's the amp that has a logarithmic treble boost with respect to input voltage, unless I'm reading this wrong. The gain is higher at high frequencies than low frequencies. Therefore, compression occurs at lower input levels at high frequencies the at low frequencies. This is why the lines get closer together at high frequencies than at low frequencies when the level is turned up on the db plot. This is a bit hard to see because this only happens at the highest few in put levels.
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Post by antigua on Apr 26, 2017 14:29:59 GMT -5
What I'm interested in finding out is if overall differences in pickup output level cause a different EQ curve which can give rise to the notion that two pickups sound different when in fact the difference is more limited to output, which I suspect might be the case with pickups with degaussed magnets. Based on the amplitudes where compression occurs, do you think there might be something to this? I will test another two to three amplifiers in order to gather more data points.
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Post by JohnH on Apr 26, 2017 16:05:55 GMT -5
Are you getting those curves by adjusting the amp vol knob, or by boosting the input before the amp?. I think that to test the effect due to pickup output, the amp would need to be set and left untouched. Otherwise circuits in the amp such as bright/treble bleed caps on the volume pots (ading treble at lower volume) will throw the results out.
EDIT: or maybe the point is, given a higher output pu, a player tends not to turn the gain or volume up quite so high to get the level they want. Then the amps bright cap tends to add relatively more treble than for a lower output pu with amp turned higher.
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Post by antigua on Apr 27, 2017 12:26:50 GMT -5
Are you getting those curves by adjusting the amp vol knob, or by boosting the input before the amp?. I think that to test the effect due to pickup output, the amp would need to be set and left untouched. Otherwise circuits in the amp such as bright/treble bleed caps on the volume pots (ading treble at lower volume) will throw the results out. EDIT: or maybe the point is, given a higher output pu, a player tends not to turn the gain or volume up quite so high to get the level they want. Then the amps bright cap tends to add relatively more treble than for a lower output pu with amp turned higher. The volume is fixed, the input is increased in all but one plot. This plot is the exception. In only this plot, is the volume knob being adjusted: The lines varied as the pre-amp tubes warmed up, it seemed that the treble disposition decreased as they were on longer, eventually settling how you see it at the top. This plot was just for the sake of comparing the two, the pickup would be represented by the input amplitude plots.
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Post by antigua on Apr 28, 2017 0:05:33 GMT -5
I tested an Ibanez TSA30 30 watt tube amp, went in the front, came out the effects send, but strangely this doesn't seem to go through a pre-amp, it looks more like it's straight through. None of the gain or EQ knobs have any effect on the output signal, so unfortunately it doesn't look like I can get a read on how it effects the signal without sampling from the speaker out. Question: the Velleman has a max input voltage of 30 volts; could I sample from the speaker output with the volume set lower? Would I need to put a resistor in series to satisfy the expected speaker impedance? Here is a little 9v battery powered Fender practice amp, in the front and out the headphone jack on the side. It looks to me like this little amp compresses in such a way that boosts the lower and higher frequencies. linear log
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zmix
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Post by zmix on May 14, 2017 9:11:57 GMT -5
I just wanted to make some general comments, and to ask a question.
As for a guitar amplifier changing it's response with gain, the simple answer is that when it's operating in a linear region, it does not (basically by definition).
A classic Marshall amp, such as a Super Lead has a 6dB/oct High Pass filter on the "bright" channel, with an Fc of 600-1000 Hz, this causes the harmonics to clip proportionally more than the fundamental, compared to more normal ("flat") amp designs, and due to the inherently high IMD of the Marshall this generates audible sum and difference frequencies, this is the basis of the "Marshall Sound™", at a moderate gain setting, the fundamentals are still rather clean and retain their "punch" but playing simple intervals, like a major third or fifth will generate sub octaves, etc, which is why such a ridiculously bright amp can sound "fat" or "chunky".
I use a bit of (free) audio testing software called "Room Eq Wizard" which is incredibly thorough and comprehensive. One capability of has that might be of interest here is that it can plot THD vs Frequency and display the amplitude of the individual harmonics across the spectrum, it also has a RTA that automatically number the harmonics in the displayed graph.
Now on to my question:
Has anyone ever measured to determine if the mechanical influence on a vibrating string of the magnetic fields of two pickups is different if one has a reversed magnetic polarity?
I'm thinking specifically about a guitar like a Telecaster, where the neck pickup's pole pieces are situated at exactly 1/4 of the length of the string, and where someone might opt for a reversed magnetic and electrical polarity in order to achieve hum cancelling when both pickups are on.
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Post by antigua on May 15, 2017 12:42:38 GMT -5
I just wanted to make some general comments, and to ask a question. As for a guitar amplifier changing it's response with gain, the simple answer is that when it's operating in a linear region, it does not (basically by definition). A classic Marshall amp, such as a Super Lead has a 6dB/oct High Pass filter on the "bright" channel, with an Fc of 600-1000 Hz, this causes the harmonics to clip proportionally more than the fundamental, compared to more normal ("flat") amp designs, and due to the inherently high IMD of the Marshall this generates audible sum and difference frequencies, this is the basis of the "Marshall Sound™", at a moderate gain setting, the fundamentals are still rather clean and retain their "punch" but playing simple intervals, like a major third or fifth will generate sub octaves, etc, which is why such a ridiculously bright amp can sound "fat" or "chunky". I use a bit of (free) audio testing software called "Room Eq Wizard" which is incredibly thorough and comprehensive. One capability of has that might be of interest here is that it can plot THD vs Frequency and display the amplitude of the individual harmonics across the spectrum, it also has a RTA that automatically number the harmonics in the displayed graph. Now on to my question: Has anyone ever measured to determine if the mechanical influence on a vibrating string of the magnetic fields of two pickups is different if one has a reversed magnetic polarity? I'm thinking specifically about a guitar like a Telecaster, where the neck pickup's pole pieces are situated at exactly 1/4 of the length of the string, and where someone might opt for a reversed magnetic and electrical polarity in order to achieve hum cancelling when both pickups are on. Thanks for that info about the Marshalls. I gave up on that line of experimentation because I wasn't getting results that favored the hypothesis. I'd have to come back to it later. Regarding magnetic string pull and pickup polarity, it doesn't matter at all. Both pickups pull on the string, regardless of whether their polarities are the same or opposite. The string is highly permeable and it adopts the orientation of the magnet below it, and so there is attraction in all cases.
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zmix
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Post by zmix on May 16, 2017 8:59:17 GMT -5
I just wanted to make some general comments, and to ask a question. As for a guitar amplifier changing it's response with gain, the simple answer is that when it's operating in a linear region, it does not (basically by definition). A classic Marshall amp, such as a Super Lead has a 6dB/oct High Pass filter on the "bright" channel, with an Fc of 600-1000 Hz, this causes the harmonics to clip proportionally more than the fundamental, compared to more normal ("flat") amp designs, and due to the inherently high IMD of the Marshall this generates audible sum and difference frequencies, this is the basis of the "Marshall Sound™", at a moderate gain setting, the fundamentals are still rather clean and retain their "punch" but playing simple intervals, like a major third or fifth will generate sub octaves, etc, which is why such a ridiculously bright amp can sound "fat" or "chunky". I use a bit of (free) audio testing software called "Room Eq Wizard" which is incredibly thorough and comprehensive. One capability of has that might be of interest here is that it can plot THD vs Frequency and display the amplitude of the individual harmonics across the spectrum, it also has a RTA that automatically number the harmonics in the displayed graph. Now on to my question: Has anyone ever measured to determine if the mechanical influence on a vibrating string of the magnetic fields of two pickups is different if one has a reversed magnetic polarity? I'm thinking specifically about a guitar like a Telecaster, where the neck pickup's pole pieces are situated at exactly 1/4 of the length of the string, and where someone might opt for a reversed magnetic and electrical polarity in order to achieve hum cancelling when both pickups are on. Thanks for that info about the Marshalls. I gave up on that line of experimentation because I wasn't getting results that favored the hypothesis. I'd have to come back to it later. Regarding magnetic string pull and pickup polarity, it doesn't matter at all. Both pickups pull on the string, regardless of whether their polarities are the same or opposite. The string is highly permeable and it adopts the orientation of the magnet below it, and so there is attraction in all cases. Thanks. I suppose that the magnetic hysteresis of a guitar string is negligible, and also that N/S fields are both present in a single pickup.
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frankfalbo
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Post by frankfalbo on May 17, 2017 23:49:15 GMT -5
I tested an Ibanez TSA30 30 watt tube amp, went in the front, came out the effects send, but strangely this doesn't seem to go through a pre-amp, it looks more like it's straight through. None of the gain or EQ knobs have any effect on the output signal, so unfortunately it doesn't look like I can get a read on how it effects the signal without sampling from the speaker out. That's because that amp was designed like having a Tube Screamer pedal in front of the tube amp. The Loop is between the Tube Screamer and the front end of the amp. Like if you had a Tube Screamer on your pedalboard, there would likely be pedals after it. It's detailed in the block diagram of the amp in the manual. www.ibanez.com/world/manual/amp/TSA30.pdf
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Post by antigua on May 18, 2017 20:16:38 GMT -5
I tested an Ibanez TSA30 30 watt tube amp, went in the front, came out the effects send, but strangely this doesn't seem to go through a pre-amp, it looks more like it's straight through. None of the gain or EQ knobs have any effect on the output signal, so unfortunately it doesn't look like I can get a read on how it effects the signal without sampling from the speaker out. That's because that amp was designed like having a Tube Screamer pedal in front of the tube amp. The Loop is between the Tube Screamer and the front end of the amp. Like if you had a Tube Screamer on your pedalboard, there would likely be pedals after it. It's detailed in the block diagram of the amp in the manual. www.ibanez.com/world/manual/amp/TSA30.pdfThanks, that's good to know. Too bad there isn't a more "true" effects loop between the pre amp and power section.
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