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To know that non linear distortion levels of 0.1%, 0.01%, and 0.001 are not audible to human beings or that increases in distortion of these orders of magnitude are also inaudible doesn't take a research project into the history of auditory measurements. Just ask any fan of vacuum tube amplifiers where distortion typically runs from 0.5% to 2% or fans of vinyl phonograph records where distortion typically runs from 2% to 5%. They will tell you those levels are also inaudible. Whatever the listening attributes of vacuum tube amplifiers or vinyl phonograph records are, from a point of view of electrical performance specifically in regard to non linear distortion, by today's state of the art standards, they stink.
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Quote:
Originally Posted by skeptic
Just ask any fan of vacuum tube amplifiers where distortion typically runs from 0.5% to 2% or fans of vinyl phonograph records where distortion typically runs from 2% to 5%. They will tell you those levels are also inaudible. Whatever the listening attributes of vacuum tube amplifiers or vinyl phonograph records are, from a point of view of electrical performance specifically in regard to non linear distortion, by today's state of the art standards, they stink.
I would like to see a controlled listening test involving the bypassing of a preamp line stage with attenuators. As in completely removing the preamp from the signal path. The unit's design (SS, tubes, hybrid) is really not critical. Why a preamp's line stage? Because it is the only one that can be superfluous with some systems. Using a high output, low impedance source like some CDPs using low cap cables to eliminate HF rolloff effects, compare the presence of the line stage to its absence. Whatever small amount of measured distortion is present with the preamp should render the comparison identical -- at least in theory. Is it?
rw
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The use of a so called "passive preamplifier" can cause serious degradation in overall system performance because in an "active preamplifier" the volume control sits between two gain stages which buffer the input and the output from the previous and succeeding stages and place the volume control potentiometer in a circuit which is specifically designed to minimize its audible effects except for a change in gain. There may be other minor frequency response changes created by some active preamplifiers which can be slightly audible but their signifigance is invariabley minimal except to those whose favorite expression is "it blew the other one away." Even vacuum tube preamplifiers if they are well designed have minimal distortion. Most audible nonlinear distortion from vacuum tube systems comes from the power output transformers whose nonlinear magnetic properties, even for the best designed units and the relatively high output impedence which reduces damping factor significantly thereby reducing the amplifier's ability to surpress spurious woofer resonances. Worse still are those whose lack of negative feedback increase non-linear distortion at least a full order of magnitude or the inexpert use of non linear feedback which can cause ringing.
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Quote:
Originally Posted by skeptic
To know that non linear distortion levels of 0.1%, 0.01%, and 0.001
Or to put it anopther way, -40, -60 and -80dB respectively.
-Bruce
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The calculations are simple to anyone who belongs in an electronics laboratory. To those who don't and wander in anyway, you can look but don't touch anything. What you don't know can kill you.
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Quote:
Originally Posted by skeptic
The use of a so called "passive preamplifier" can...
I am aware of the theory and the potential issues. Which is why I qualified certain conditions. Can a 75 ohm output source comfortably drive an amplifier with a 137k ohm input resistance?
rw
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Quote:
Originally Posted by E-Stat
Interesting. I guess that is a sad commentary on cultural literacy today. They should have asked a second grader who would know the difference.
rw
While I agree with the literacy statement, that is not the point, because any other example could have been applied. The point being made is that it is exceptionally easy for people to dream up things that didn't happen and believe that they did. A fantasy.
-Bruce
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Wrong Again Bruce
Quote:
Originally Posted by FLZapped
Or to put it anopther way, -40, -60 and -80dB respectively.
-Bruce
Those levels of distortion represent -60, -80 and -100 dB respectively.
Well, you were only off by 20 dB, what's a few dB among friends?
Jon Risch
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Not quite right
Quote:
Originally Posted by skeptic
To know that non linear distortion levels of 0.1%, 0.01%, and 0.001 are not audible to human beings or that increases in distortion of these orders of magnitude are also inaudible doesn't take a research project into the history of auditory measurements.
I do believe that the higher orders of distortion, the 5th, and definitely the 7th and up, would be audible at 0.1%. However, that is still a moot point, and not what I was getting at.
Those numbers DO NOT have a ready correlation with the measured results from an audio device, for the very reason I just mentioned: we are more sensitive to the higher order distortion products. In many cases, we can not hear 1% 2nd harmonic, or a 2nd order type distortion, and THAT's why some tube amps sound better than they measure, they tend to have low order distortion, while SS amps with lot's of feedback tend to have lots of higher order distortions.
There is no simple metric, such as "less than 0.1% is inaudible", the papers aren't there, the correlation is not there. You can continue to ignore these aspects of audio, but sticking you head in the sand does not make the truth go away.
Jon Risch
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In a thread John Curl published and which was quoted here a year or two ago, he boasted that he had some of the most sensitive distortion measuring equipment in the world and that the greatest difference he could measure between the best interconnect cables and the worst which were $1 Radio Shack was minus 135 db versus minus 120 db of the 7th harmonic of 5 khz. If there was even the slightest doubt in my mind that Radio Shack cables weren't as good as I could hear for an audio system, that dispelled the last of it.
Wanna go backwards in time and argue digital jitter again and tell me one more time why digital jitter from audio cables is audible while digital jitter thousands of times greater from the spinning disc isn't?
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Quote:
Originally Posted by J Risch
I do believe that the higher orders of distortion, the 5th, and definitely the 7th and up, would be audible at 0.1%. However, that is still a moot point, and not what I was getting at.
Those numbers DO NOT have a ready correlation with the measured results from an audio device, for the very reason I just mentioned: we are more sensitive to the higher order distortion products. In many cases, we can not hear 1% 2nd harmonic, or a 2nd order type distortion, and THAT's why some tube amps sound better than they measure, they tend to have low order distortion, while SS amps with lot's of feedback tend to have lots of higher order distortions.
There is no simple metric, such as "less than 0.1% is inaudible", the papers aren't there, the correlation is not there. You can continue to ignore these aspects of audio, but sticking you head in the sand does not make the truth go away.
Jon Risch
Jon
Having little interest in the topic overall, I did not read your preprint..
1.. Did you correlate standard tests against yours?
2.. Did you do this using resistive loads or reactive loads, and to what power levels.
3.. Did you show distortion products that rise above accepted jnd's which otherwise did not?
Why has industry not adopted a test methodology that you claim is better?
Does your current employer, Peavey, use it? After all, you submitted it under their auspices..and I assume, they paid for it..
Or, are you alone in your beliefs.
Cheers, John
PS..."what's a few dB among friends?"
Now THAT was funny... (sorry Bruce)
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Quote:
Originally Posted by skeptic
In a thread John Curl published and which was quoted here a year or two ago, he boasted that he had some of the most sensitive distortion measuring equipment in the world and that the greatest difference he could measure between the best interconnect cables and the worst which were $1 Radio Shack was minus 135 db versus minus 120 db of the 7th harmonic of 5 khz. If there was even the slightest doubt in my mind that Radio Shack cables weren't as good as I could hear for an audio system, that dispelled the last of it.
As I recall, Curl eventually tempered his claims down to "the distortion products may correlate to some other as yet unknown phenomena", instead of claiming that the distortion levels were audible..
Although, I do not agree with him that the wires were actually causing it..I still believe it was a test equipment issue.
Quote:
Originally Posted by skeptic
Wanna go backwards in time and argue digital jitter again and tell me one more time why digital jitter from audio cables is audible while digital jitter thousands of times greater from the spinning disc isn't?
I would personally love to see how a spinning low mass disk of plastic can have it's rotational velocity controlled to the extent that data is presented to the read laser at low jitter levels...levels which can be altered by a sandbag on the crystal..
Course, I think an argument can be presented to show how the electronics that read the data can alleviate the physical limitations of the disk motor..so I think, the actual question would be, does a 20 picosecond jitter do anything further down the line? And, could a sandbag do anything to that?..
But, I think the topic in this thread is the JR distortion signal and how it is stated as being better than everyting else..
I'd love to hear an explanation about how superposition does not apply to the electronics..
I'll even give a hint....silicon transient thermal behaviour has a time constant of 10 uSec at the die surface, about 100 uSec to die backside, and 10 mSec to the heatsink. and all of these thermal time constants are inaccessible by the outside world when the die is connected to electronics...I know, I have tested all those time constants..
And, I have this nagging concern that FFT's can't readily discern some of the distortion products..no facts, just a gut feel...and no, I haven't had any Thai food lately..
Welcome back....
Cheers, John
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"As I recall, Curl eventually tempered his claims down to "the distortion products may correlate to some other as yet unknown phenomena"
Yes, the ghosts of dead aliens killed when their spacecraft crashed in the Nevada desert.
"I would personally love to see how a spinning low mass disk of plastic can have it's rotational velocity controlled to the extent that data is presented to the read laser at low jitter levels...levels which can be altered by a sandbag on the crystal..
Course, I think an argument can be presented to show how the electronics that read the data can alleviate the physical limitations of the disk motor..so I think, the actual question would be, does a 20 picosecond jitter do anything further down the line? And, could a sandbag do anything to that?.."
The obvious answer is that the digital jitter of the cable is insignificant especially in relation to the relatively enormous jitter of the rotating disc. The mere supposition that it matters goes to the heart of the lack of understanding of how bit stream technology works. The stream MUST be buffered, it MUST be reclocked, and the waveform MUST be regenerated by a Schmidt trigger or it won't work. If for any reason this scheme breaks down by say depleting the buffer registers, the entire process fails catastrophically. If it is momentary, you hear a characteristic click. Sustained and you get nothing. That is one of the many beauties of it. If it works properly, you can make a thousand generations of copies and the last generation will be indistinguishable from the first (no matter what digital cable you use.) The reason I brought it up is it was one of the more obvious blunders in Mr. Risch's last round of arguements he had with me several years ago. If he is right, I am saddened that it is no longer accessible. It was a classic debate.
There should be no doubt about the signifigance or importance of What Mr. Risch is asking us to accept. IF, and that's a very big IF, he is proven right, the entire method the audio industry uses to design and evaluate all of its products will change forever. Any scientist or engineer I ever met who would contemplate effecting such a revolutionary change would compose a very scholarly exposition of his theory and a demonstration of how it worked. He would answer a million questions and if he supplied the right answers, new test equipment would emerge, design engineers would go back to school, and evey piece of gear in every data base would be revisited to better understand it in light of the new knowledge. Did Mr. Risch do any of that? No, not this time and not in the past. He published it on a web site, it was written up in a consumer magazine, and is now being discussed on an internet chat board most of whose readers don't have the foggiest. Is that good enough? No, not for me, and not for other engineers and scientists. I hope Mr. Risch presents his paper. Then it will get the trial by fire all such proposals are subjected to. I'm sure it will be subjected to far more critical scrutiny than anything I could ever dream up.
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One last try for FLZapped
Quote:
Originally Posted by FLZapped
Interesting, trying to use IM as HD, and blame me for your confusion. Right.
If you would bother to re-read your reply, it is you who started going off on IM, when I was talking about HD. Not my confusion here. (the format I see when reading and posting here does not lend itself to reading a coherent thread of posts and replies, argh!)
Quote:
Originally Posted by FLZapped
What you described by any standard is IM distortion. Not Harmonic distortion. By world-wide recognized standards, harmonic distortion is measured with a single tone and is supported mathmatically. Intermodulaton is measured with multiple tones. These are given definitions that the rest of the engineering world recognizes as a standard, except you, apparently.
Bruce, I will use a very simple and straight-forward example, perhaps this will register.
In a previous comment, I mentioned that one could gather harmionic distortion data from a test signal with more than one tone, using the classic IM test signal pairs as an example. Now I will step through it, and I want you to then tell me specifically how what I have said is wrong, or untrue, or can not be done.
If we examine the classic SMPTE IM signal, it consists of a 60 Hz tone, and a 7 kHz tone. Now if we tried to use the old style measurement equipment, that used filtering to remove the 60 Hz component, and then looked at the amount of 7 kHz modulation, or the side bands, you would not be able to discern anything but what the machine was designed for, it is hard wired to do one thing (perhaps similar to your brain? ;-) )
But we can take that same SMPTE signal, and run it into an FFT spectrum analyzer, and see all possible distortion components that might get generated. If we looked at the IM signal source directly into the analyzer, and the source was clean, then all we would see is 60 Hz, and 7 kHz. However, once we run that through an audio device under test, which has some distortion, and feed that into the spectrum analyzer, we will now see ALL the distortion products that were generated, INCLUDING any harmonics.
There would be the IM distortion products at 7060 Hz, and at 6940 Hz, as well as the 3rd order products at 7120 Hz and 6880 Hz. However, that is not all that will likely be present.
There will also be harmonic distortion products at 120 Hz and 180 Hz, as well as 14 kHz, and 21 kHz. These will be clearly displayed on the spectrum analyzer, and can be measured relative to the level of the fundamentals, and the amount of HD calculated.
Thus, what is normally considered to be an IM test signal, with two tones, can also be used to check for harmonic distortion (but only at those two primary tone frequencies, we still don't know what kind of HD will occur at other frequencies, say, in the midband at 1 kHz). Your statement that "1) You can ONLY merasure harmonic distortion with a sing le tone" is not correct, and has been shown to be false.
My Phi Spectral multitone test signal is an extension of this same technique, only it uses either 6, or 10 or 12 tones, all of which are spaced so as to avoid any significant cover-up of one particular distortion product by another. That is the big deal with my test signal, it avoids the common error commited by ALL the other multitone test signals that went before. Not only that, but because each distortion product has a unique frequency, you can determine which tones (or a tone and another distortion product) were responsible for it, again, something that you could not do with the other commonly available multitone test signals that were available then. The AP FASTTEST signal is a good exaple, with primary tones at 1/3 octave intervals, you can not see hardly ANY of the HD products, OR any of the IM products, they are all going to end up landing right where there is already another primary tone, effectively rendering them invisible.
Quote:
Originally Posted by FLZapped
Devices are either linear, or they are not. Either they produce distortion products, or they don't.
The physics don't change with the operating frequency.
Actually, they do change with frequency in audio devices, that is exacty what I have been trying to tell you! It is very common for audio devices to have a lower level of HD in the midband, and then have much higher levels at the frequency extremes, say at 100 Hz and at 10 kHz. There are thermal considerations, biasing and operating points that changes with level and frequency, etc. so you CAN NOT make the same kind of prediction that you can with RF amps. This is not someting that any audio engineer or tech would need citations or references for, it is common knowledge, but if one really were that much in the dark, all you would ahve to do is look at some of the Stereophile test reports that are available online, and see that HD levels change with frequency.
Quote:
Originally Posted by FLZapped
Again, you think the physics change? Did you miss the fact that your engineering text book doesn't have a seperate section on defining harmonic and intermodulation distortion for audio vs rf?
Please, get real, the engineering textbooks do not call out every conceivable real world situation, and the whole idea of going to school was to learn to THINK, not regurtigate the text books. The data is out there, audio amps, and other audio devices have HD and IM that vary with level, with frequency, even vary with the past signal history of the device!!!
Quote:
Originally Posted by FLZapped
Yet you think it is okay for you to espouse several different laws of physics as to how IM and harmonic distortion are generated at audio vs rf. Yet you say we are violating the laws of physics? I have yet to see you show anywhere which ones are actually being violated. You're just hand waving.
I am not the one hand waving here, or sticking to a very narrow and outdated view of how one can measure audio equipment.
Quote:
Originally Posted by FLZapped
Enough of this squirming around to deflect the real purpose of this discussion:
Your multi-tone test signal is completely unusable to measure intermodulation distortion and is a violation of the recognized definition in measuring harmonic distortion.
Two tones, are all that's needed for IM. Regardless of operating frequency.
Harmonic distortion is measured using a single tone, regardless of operating frequency.
This is recognized world-wide and has been so for a long, long time and no one has proven otherwise. Including you.
My Phi Spectral test signal is not unusable to measure HD or IM, in fact, it is superior to the classic one tone HD and two tone IM tests, in that it streses the DUT with multiple tones, more like real music.
Two tones for IM ONLY show us what the DUT is doing WITH THOSE TWO FREQUENCIES and not for anything else.
HD can be neasured using more than one tone, as I have shown above, and can be measured using the proper type of multitone signal, one that avoids distortion product cover-up, such as my Phi Spectral multitone.
Quote:
Originally Posted by FLZapped
Even your test signal follows these laws. The problem is, your test signal will generate SO many products it would be impossible to distinguish noise from distortion products making it unusable as a viable test signal.
This is just not so, and as I have stated before, and spelled out in the paper, with the aid of a spreadsheet (or a computer program that ca generate all the possible distortion combinations and the resulting frequencies) that shows the various combinations possible, one can determine exactly where a given HD or IM product came from, or at what frequency an HD or IM product will appear. Since they do not cover one another up, they can be individually distinguished.
Yes, IF the S/N ratio of the DUT is so poor, that the noise is high and at similar levels to the distoriton products, then we will not be able to see or detect the distortion for the noise, BUT THIS IS TRUE FOR _ANY_ TEST SIGNAL, INCLUDING THE CLASSIC ONES YOU KEEP HARPING ON.
If you refuse to think, and refuse to consider anything other than what you already 'know',. then there is no point in discussing this further, and I think that other people will be able to see my points clearly, and draw there own conclusions.
Jon Risch
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Try a different mode
Quote:
Originally Posted by J Risch
(the format I see when reading and posting here does not lend itself to reading a coherent thread of posts and replies, argh!)
There is a solution to the default "linear mode" thread presentation. Scroll near the bottom and look to left for the display options. You can return to the original style or choose the middleground hybrid.
rw
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You sure ask a lot of questions!
Quote:
Originally Posted by jneutron
Having little interest in the topic overall, I did not read your preprint.
That begs the question: why so many questions now? At least yours make some sense.
You really should read the paper, I have the text at:
http://www.geocities.com/jonrisch/PhiSpectral1.htm
be sure to click all three pages worth.
Quote:
Originally Posted by jneutron
1.. Did you correlate standard tests against yours?
I did to a limited extent, using primarily loudspeakers, plotting 2nd and 3rd harmonic against the Phi Spectrals. I had two comparisions in my paper, but one of the graphics got left out (I handed out the mising sheet at the convention for those who attended)
Quote:
Originally Posted by jneutron
2.. Did you do this using resistive loads or reactive loads, and to what power levels.
Real loudspeakers. If you meant for power amps, I did not do extensive testing of power amps as a separate category, but since the paper, I have measured a few more, and the big thing is, doing so at different power levels.
Quote:
Originally Posted by jneutron
3.. Did you show distortion products that rise above accepted jnd's which otherwise did not?
I did show distortion levels that exceeded the simple IM or classic HD plots by 10-12 dB, however, some folks would have argued that some of the HD levels were already above audibility, however, I was able to show that a speaker tha measured "OK" by HD metrics, measured much worse using the Phi Spectrals, while another speaker that measured similarly to the first one on HD, remained low on the Phi Spectral. This was one of my points of evidence for the superior resolving power of the Phi Spectral.
Quote:
Originally Posted by jneutron
Why has industry not adopted a test methodology that you claim is better?
The industry is all over the map, the current simple and limited measurements we have today evolved over a period of many years, and it took years and years for the industry to agree on some of those standards. I do believe that it took almost 10 years for the SMPTE IM standard to be offically adopted, and look how simple that is!
I can say that Klipsch and Cerwin-Vega are using it, or have used it at one time, there may be more than that, most folks would NOT advertise they were using such a powerful tool, if they felt that by keeping under the radar, they would keep other folks from noticing and using it too.
Quote:
Originally Posted by jneutron
Does your current employer, Peavey, use it? After all, you submitted it under their auspices..and I assume, they paid for it..
Or, are you alone in your beliefs.
I can't really comment on that specifically, suffice it to say, that we could not have developed a 4" format compression driver to have distortion as low or lower than a TAD driver, at about 1/4 the cost, just by accident.
I can also say that I work with many groups within Peavey, including the power amp folks, the guitar folks, and even at times, the digital engineering guys. I can not go any further than that.
BTW, ALL of the time I spent on developing and researching the Phi Spectral was on my own time, after hours or at home. I even paid my own way to the AES convention, which is another story, and one I am also not at liberty to discuss.
For the future:
I have been working with some folks on a super version of this, one that will be wholly integrated into a computer controlled environment, so that much of the analysis would be automated and made easy to view and interpret, as well as a VERY neat twist that will make it even more powerful and relevant to measuring audio devices! This may take a bit of time though, as we are talking about some other guys working in THEIR spare time.
Should be a very interesting end result, if we can get it to do what I think it can.
Jon Risch
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So much vitriol, so little science....
Quote:
Originally Posted by skeptic
The obvious answer is that the digital jitter of the cable is insignificant especially in relation to the relatively enormous jitter of the rotating disc. The mere supposition that it matters goes to the heart of the lack of understanding of how bit stream technology works. The stream MUST be buffered, it MUST be reclocked, and the waveform MUST be regenerated by a Schmidt trigger or it won't work. If for any reason this scheme breaks down by say depleting the buffer registers, the entire process fails catastrophically.
This is, of course, a diversion from the main topic, which you seem to know very little about. However, to set the record straight (since the old posts are not really there anymore), I am compelled to correct your misinformation.
Of course there is buffering, there is reclocking, there is crystal control IN SOME CASES (but not all), but that was not the crux of the matter as far as the use of a separate transport and DAC are concerned.
As I spell out at this page:
http://www.geocities.com/jonrisch/jitter.htm
all of these actions you describe, the reading of the data, the buffering, the reclocking, the reshaping, all of them affect the power supply, cause transient drains on the PS rails (and cause ground bounce as well) that occur more or less in time with the activity that is going on, and at the basic clock rate (and submultiples) within the player. There are also drains and transients that are not at the clock rate or submultiples, these would be the analog output stage itself, the read servo and motor speed circuit, etc. The result of all of this activity impinging on the PS is that the device that actually converts the digital data into an analog signal, the DAC, is being presented with a PS rail and ground that have a sing song related to the digital signal activity, that is related to the servo activity, that is related to the motor speed adjustment activity, etc. and all of these things are going to introduce timing errors into the conversion within the DAC. Timing errors known as jitter.
(As noted at my page, even if the DAC were presented with a perfect PS and ground, it is still subject to internal LIM.)
So even with buffering, recloking, reshaping, YOU CAN'T GET AWAY FROM THE PS MODULATION.
Now all of this occurs within ANY CDP, not just a transport and DAC combo, but when we look at a transport/DAC combo, we find that there have been added to this PS sing-song, additional PS transients due to the presence of the SP/DIF output, and due to the receiver circuity, and additional jitter due to the finite bandwidth of the cable (and of the digital output/input circuits as well) and the less than perfect noise and interference rejection of the cable and receiver.
Those things that you were talking about before? The buffering? The reclocking? The reshaping? Those all tend to reduce the raw jitter coming off the disc down to levels that are now limited more by the PS sing-song that is going on, than the raw disc variations.
Once we introduce a digital IC between a transport with it's digital output, and a DAC, with it's receiver circuit, we have ADDED to this PS sing-song as well as introduced additional jitter directly due to the cable and transceiver bandwidth limitations, and THIS is why a digital cable can have the effect it does.
Quote:
Originally Posted by skeptic
The reason I brought it up is it was one of the more obvious blunders in Mr. Risch's last round of arguements he had with me several years ago.
In your dreams again. I suppose you would see it that way, but not too many others did (the usual naysayers were cheering you on, but they didn't really know what was going on in the first place).
Quote:
Originally Posted by skeptic
There should be no doubt about the signifigance or importance of What Mr. Risch is asking us to accept. IF, and that's a very big IF, he is proven right, the entire method the audio industry uses to design and evaluate all of its products will change forever.
Indeed. And some of us are using it already. :-)
Quote:
Originally Posted by skeptic
Any scientist or engineer I ever met who would contemplate effecting such a revolutionary change would compose a very scholarly exposition of his theory and a demonstration of how it worked. He would answer a million questions and if he supplied the right answers, new test equipment would emerge, design engineers would go back to school, and evey piece of gear in every data base would be revisited to better understand it in light of the new knowledge. Did Mr. Risch do any of that? No, not this time and not in the past. He published it on a web site, it was written up in a consumer magazine, and is now being discussed on an internet chat board most of whose readers don't have the foggiest. Is that good enough? No, not for me, and not for other engineers and scientists. I hope Mr. Risch presents his paper.
I did present it, at the 105th Convention of the Audio Engineering Society
in September of 1998, in San Francisco, CA as preprint #4803.
I presented to a packed hall, and was asked a lot of questions, but with the usual scene at the conventions of things running late, I was asked to take the bulk of the questions out in the hall, where I distributed approx. 30 CD-R's containing tracks with the multitone signal on it, and diskettes with the spreadsheet. I collected approx. 27 bussiness cards for those who still desired a set of discs, and mailed those out at my cost, to those people.
Since that presentation, I have gone through two batchs of paper hardcopy preprints, not counting the numerous electronic copies I have sent out at request.
A. Voishvillo of Cerwin Vega has cited my paper in his work on multitones, and as I said in the opening post here, people from all over the world have expressed interest, and asked for a copy, or asked questions about the paper, or asked questions about different versions of the Phi Spectral multitone.
My presentation at my web site, and at this forum, are complementary, and in addition to the one at the AES..
Jon Risch
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This is going to read as if I'm replying to Jon, but it applies to the thread in general.
Yes, let's keep this on topic. If there are other issues that people would like to discuss, please start other threads about them.
Also, I think all of us (myself included) can probably tone down the personal invective. For the most part, I think this exchange has gone amazingly well, and it's been very interesting and informative, and I for one would really like to keep it that way.
I don't have any particular technical knowledge or experience related to this subject, so take my opinion for what it's worth, but based on the arguments given in this thread, I'm not seeing a sufficient rationale for taking the position that Jon's test method is without merit. The argument that his new method somehow suggests that the previous methods are wrong seems to be particularly flawed, since scientific advancement historically doesn't seem to be so much about disproving previous understanding, as it is about providing more clarification and refinement of previous understanding. Unless one holds the position that the current methods and abilities of distortion measurement are inclusive of all relevant aspects, and will forever continue to be so, then I think common sense suggests that methods of acquiring more data would be beneficial, IF that data can prove to bear out some experiential corellation, as Jon suggests his method indeed does.
Also, and perhaps this is more significant, nobody seems to be disputing the validity of the actual test method itself, nor the figures Jon claims to have generated by using it. And I don't believe that anybody said a thing about Jon's claim that using his method enabled him to discover problems with the digital filters in some of the CD players he tested. That purpose alone would seem to be an eminently useful aspect of his method, even if it's potential elsewhere remains in dispute.
I think someone asked if I was "pretending"(?) about wanting people's opinions about this subject. I was not. What piqued my interest in this was reading a review of some Simaudio component, and the reviewer stated that the product literature mentioned that Simaudio try to eliminate IM from their products, because they think it's more detrimental to sound quality than HD. Jon has a test method for measuring these that's different than any I'd read about anywhere else, so, here we are.
Jon, I'd appreciate it if you could elaborate on what you meant about the "past signal history" portion of this statement:
Quote:
Originally Posted by J Risch
The data is out there, audio amps, and other audio devices have HD and IM that vary with level, with frequency, even vary with the past signal history of the device!!!
That's a new one for me.
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"I don't have any particular technical knowledge or experience related to this subject"
You are correct. Technically, you are way out beyond your depth. You don't have even the slightest understanding of what this debate is really about. It's about overturning hundreds of years of mathematics and nearly a century of electrical measurement science. If it's true, it's genius. If it isn't, it's worthless trash.
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"A. Voishvillo of Cerwin Vega has cited my paper in his work on multitones"
So far an army of two? Well at least it's a start. How ironic that one of your first supporters should come from a company whose products' only redeeming virtue as I see it is that they allow music haters to become permanently and profoundly deaf at the lowest possible cost. :-)
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Originally Posted by J Risch
That begs the question: why so many questions now?
Umm, well...because there are 65 posts on the topic, just before mine..and parts of the discussion have tweaked my interest..
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Originally Posted by J Risch
I can also say that I work with many groups within Peavey, including the power amp folks, the guitar folks, and even at times, the digital engineering guys. I can not go any further than that.
A simple yes or no would have sufficed, as you are working for a company which derives profits from their work..I cannot expect IP to be divulged.
Although I work for the DOE and am required to publish what I do on our web pages, in publications, at conferences, and in seminars, not all of it is revealed..we tend to gloss over the high falutin stuff, and present lower level synopsis' of techniques and analysis for the scientific and engineering communities, so that they can understand what the end product is and how difficult it is to get there...
Cheers, John
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Originally Posted by J Risch
Those levels of distortion represent -60, -80 and -100 dB respectively.
Well, you were only off by 20 dB, what's a few dB among friends?
Jon Risch
You are correct. I missed thinking about 10% being the first step and jumped to 1%. My bad.
-Bruce
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Originally Posted by J Risch
Bruce, I will use a very simple and straight-forward example, perhaps this will register.
My, my, look how quickly the ad hominem attacks begin. hardly out of the first paragraph.
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Actually, they do change with frequency in audio devices, that is exacty what I have been trying to tell you! It is very common for audio devices to have a lower level of HD in the midband, and then have much higher levels at the frequency extremes, say at 100 Hz and at 10 kHz. There are thermal considerations, biasing and operating points that changes with level and frequency, etc. so you CAN NOT make the same kind of prediction that you can with RF amps. This is not someting that any audio engineer or tech would need citations or references for, it is common knowledge, but if one really were that much in the dark, all you would ahve to do is look at some of the Stereophile test reports that are available online, and see that HD levels change with frequency.
That has nothing to do with the basic physics involved. The products are still there as predicted.
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My Phi Spectral test signal is not unusable to measure HD or IM,
It is completely unusable to make meaningful measurements. As you said, it would take a massive spredsheet to sort out all the possible combinations especially when you include multiple order products. The results would be indistinguishable from noise.
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in fact, it is superior to the classic one tone HD and two tone IM tests, in that it streses the DUT with multiple tones, more like real music.
That's what we have pink noise for. Again, a world-wide recognized standard.
The rest I have already covered.
-Bruce
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Originally Posted by skeptic
You are correct. Technically, you are way out beyond your depth. You don't have even the slightest understanding of what this debate is really about..
Which of course has absolutely no bearing on my intelligence or deductive reasoning abilities for the purposes of this thread. Really, the posturing and hyperbole are not helping your argument.
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It's about overturning hundreds of years of mathematics and nearly a century of electrical measurement science.
I don't see that it does any such thing. Jon clearly based his new test method on the already-existing methodology, which would make his version simply an evolution and refinement of the previous approach, much like the way progress in other scientific fields has occurred.
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If it's true, it's genius. If it isn't, it's worthless trash.
And history is replete with people who thought outside the box of conventional scientific wisdom, were reviled at the time for doing so, and were later proven to have been correct. Although I don't have the technical wherewithal to evaluate Jon's data, you and others apparently do, but instead of giving it an honest scientific evaluation, I'm seeing a response that seems to be mostly predicated on non-scientific and decidedly human considerations. Sometimes the apple cart gets upset, that's just the way life goes.
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Originally Posted by FLZapped
It is completely unusable to make meaningful measurements. As you said, it would take a massive spredsheet to sort out all the possible combinations especially when you include multiple order products. The results would be indistinguishable from noise.
This I'm still not clear on. If it's necessary to obtain results out to the nth degree for the method to have any usefulness, how do you explain the results Jon did obtain, since he presumably did not do that? Certainly limiting the calculations to some established threshold would make them easier to interpret, but would doing that also automatically invalidate the results?
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