something very cool
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bcarso
Well-known member
Seems like a sound analysis at first glance.
The desirable thing, then, would be to provide the appropriate linearization to the instantaneous amplifier output voltage to correct. You could calibrate this for a given mic with a good acoustic reference source, and tune the curve of your linearizer to minimize distortion.
The desirable thing, then, would be to provide the appropriate linearization to the instantaneous amplifier output voltage to correct. You could calibrate this for a given mic with a good acoustic reference source, and tune the curve of your linearizer to minimize distortion.
I can't help thinking that there's a basic falacy here......
The calculations are talking about a few megohms loading capacitances of around 50pF; if the load resistance rises, the distortion effects are displaced downwards in frequency.
I'm not into mic design right now, but these effects were around and known ten years ago when I was playing with mic designs... and with the inherrent capacitances and load resistances I was using, the effect was not significant.
Yes, everything matters, but the cancellation effects across the face of a large diameter capsule are very much more significant, yet the big capsules sound best!
The calculations are talking about a few megohms loading capacitances of around 50pF; if the load resistance rises, the distortion effects are displaced downwards in frequency.
I'm not into mic design right now, but these effects were around and known ten years ago when I was playing with mic designs... and with the inherrent capacitances and load resistances I was using, the effect was not significant.
Yes, everything matters, but the cancellation effects across the face of a large diameter capsule are very much more significant, yet the big capsules sound best!
Ted
I read Dan's forum almost every day.
He is looking at stuff very close maybe even finding thing others might have overlooked. I believe you need to understand why the human ear brain like or dislikes certain things and looking at things a a very basic level can be a very good thing. Yes the input R might be low but it does show a change. If I understand capsules right the cap change is the instant average of all the distances between the skin to backplate.
I have read the paper and I have not seem him state it effects the sound: however the 2nd part is interesting how the curve was made more a straight line with a "pad" cap. I think Dale was on to something like this with one of microphone builds.
The web makes me sad if you read the vacuum tube microphone thread at his site some people are bringing stuff up that has nothing to do with the thread and wasting his time instead of maybe learning something.
This PDF and the the current distortion threads here are very interesting to me.
I read Dan's forum almost every day.
He is looking at stuff very close maybe even finding thing others might have overlooked. I believe you need to understand why the human ear brain like or dislikes certain things and looking at things a a very basic level can be a very good thing. Yes the input R might be low but it does show a change. If I understand capsules right the cap change is the instant average of all the distances between the skin to backplate.
I have read the paper and I have not seem him state it effects the sound: however the 2nd part is interesting how the curve was made more a straight line with a "pad" cap. I think Dale was on to something like this with one of microphone builds.
The web makes me sad if you read the vacuum tube microphone thread at his site some people are bringing stuff up that has nothing to do with the thread and wasting his time instead of maybe learning something.
This PDF and the the current distortion threads here are very interesting to me.
Martin B. Kantola
Well-known member
- Joined
- Jun 24, 2005
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- 209
[quote author="Gus"]
The web makes me sad if you read the vacuum tube microphone thread at his site some people are bringing stuff up that has nothing to do with the thread and wasting his time instead of maybe learning something.[/quote]
Would you care to be more specific, since "some people" might actually be reading this? I'm sure they would like to know that they are waisting somebody's precious time... :?
No seriously, back to the topic, it's a very interesting thought in Dan's paper, has anybody figured out yet how much distortion the error in fact would be comparable to?
Martin
The web makes me sad if you read the vacuum tube microphone thread at his site some people are bringing stuff up that has nothing to do with the thread and wasting his time instead of maybe learning something.[/quote]
Would you care to be more specific, since "some people" might actually be reading this? I'm sure they would like to know that they are waisting somebody's precious time... :?
No seriously, back to the topic, it's a very interesting thought in Dan's paper, has anybody figured out yet how much distortion the error in fact would be comparable to?
Martin
I did not state names hopefully not to hurt peoples feelings.
Martin I did not have problem with your posts.
The posts about tubes being more linear than solid state devices are the ones. You can make a gain stage very linear with solid state if you don't limit yourself to one active part.
Dan did not post linear was better for a microphone and I "think" that is what people could not get around.
Yes I often like a tube microphone more than a solid state one but I don't think it is because it is more linear. Solid state can sound very good if done right and what is right changes with what a designer wants from a microphone.
I posted in the thread about tube curves use if you look at the tube curves and operating points and currents of some "classic" designs they are down in the curved section, curved means harmonics.
Then look at the ela m25x circuit look carefully at the grid to ground Rs used.
I think about microphone every day read a study read and study and build. that why I like the pdf it is interesting maybe it has something to do with the 251.
Martin I did not have problem with your posts.
The posts about tubes being more linear than solid state devices are the ones. You can make a gain stage very linear with solid state if you don't limit yourself to one active part.
Dan did not post linear was better for a microphone and I "think" that is what people could not get around.
Yes I often like a tube microphone more than a solid state one but I don't think it is because it is more linear. Solid state can sound very good if done right and what is right changes with what a designer wants from a microphone.
I posted in the thread about tube curves use if you look at the tube curves and operating points and currents of some "classic" designs they are down in the curved section, curved means harmonics.
Then look at the ela m25x circuit look carefully at the grid to ground Rs used.
I think about microphone every day read a study read and study and build. that why I like the pdf it is interesting maybe it has something to do with the 251.
bcarso
Well-known member
I haven't read the thread(s) in the other forum(s) but is there a mention of the kinds of SPL that would correspond to these large capacitance variations?
Another thing that occurs to me is that, at those displacements the validity of Hooke's Law for the diaphragm may also be a significant consideration for any linearity/distortion issues. In this case I would expect the deviation from linearity to be mostly symmetrical about the zero SPL point, slightly offset by the initial displacement due to the electric field, hence leading to mostly odd-order distortion.
One of the problems with measurements of transducers like this one is getting a guaranteed clean test signal to begin with. I wonder if anyone has done something similar to the things Klippel and that other outfit do for loudspeakers, where the pressure on each side of the transducer is changed by an external regulated pump to produce the displacement? Applied to capsules this would not give you the whole story of course, basically operating at "d.c.", and neglecting a whole lot of other details like backwaves/reflections/damping, grill effects, modal breakup, etc., but it could provide some useful data on these basic issues of force, displacement, and displacement-dependent capacitance.
The instrumentation for a capsule could be simpler, probably relying on heights of fluids in a barometer-like arrangement. Safer too....
Another thing that occurs to me is that, at those displacements the validity of Hooke's Law for the diaphragm may also be a significant consideration for any linearity/distortion issues. In this case I would expect the deviation from linearity to be mostly symmetrical about the zero SPL point, slightly offset by the initial displacement due to the electric field, hence leading to mostly odd-order distortion.
One of the problems with measurements of transducers like this one is getting a guaranteed clean test signal to begin with. I wonder if anyone has done something similar to the things Klippel and that other outfit do for loudspeakers, where the pressure on each side of the transducer is changed by an external regulated pump to produce the displacement? Applied to capsules this would not give you the whole story of course, basically operating at "d.c.", and neglecting a whole lot of other details like backwaves/reflections/damping, grill effects, modal breakup, etc., but it could provide some useful data on these basic issues of force, displacement, and displacement-dependent capacitance.
The instrumentation for a capsule could be simpler, probably relying on heights of fluids in a barometer-like arrangement. Safer too....
When I get a chance I will hookup a scope to the output of my tlm103 and/or nt1000 k2 all are unity gain amps I believe. I think the 103 uses 60V for the capsule. I am not setup to measure the capsule with full voltage but I will measure it with a lc102. I might make a CF microphone for this test
Marik
Well-known member
I posted answer on Dan's forum before I read this thread. Indeed, it is a very interesting paper.
Although these kinds of nonlinearity might be less dominant than some others, it is a very good start.
Knowing how meticulous Dan is, I am sure this paper will go through modifications and refinments for much broader and complete picture.
Keep your eye on it!
Although these kinds of nonlinearity might be less dominant than some others, it is a very good start.
Knowing how meticulous Dan is, I am sure this paper will go through modifications and refinments for much broader and complete picture.
Keep your eye on it!
I looked up the tlm specs at neumanns site ~=3.5V is listed in the tlm section of the "microphones" PDF if I read it correctly (page 67 of the pdf "microphones")
I think a safe guess for capsule cap would be 55pf to 80pf (I have not measured my 103 capsule) I would also guess 60VDC
60V X delta cap change/say60pf(to make it easy) would be about 1pf a volt out so maybe the max change in a neumann LD might be 3 to 4pf.
EDIT
13DBu is about 3.5 rms so it would be more like 9.8VP-P
so the change would be more like 4.4 pf each way from rest.
I think a safe guess for capsule cap would be 55pf to 80pf (I have not measured my 103 capsule) I would also guess 60VDC
60V X delta cap change/say60pf(to make it easy) would be about 1pf a volt out so maybe the max change in a neumann LD might be 3 to 4pf.
EDIT
13DBu is about 3.5 rms so it would be more like 9.8VP-P
so the change would be more like 4.4 pf each way from rest.
Marik
Well-known member
[quote author="Gus"]
so the change would be more like 4.4 pf each way from rest.[/quote]
Gus,
I am wondering why each way and not one way? Sound wave hits the diaphragm from one side (well, from both if you think about back side of the capsule, but its energy mostly gets absorbed by resistive network and air cution).
so the change would be more like 4.4 pf each way from rest.[/quote]
Gus,
I am wondering why each way and not one way? Sound wave hits the diaphragm from one side (well, from both if you think about back side of the capsule, but its energy mostly gets absorbed by resistive network and air cution).
