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Old 7th November 2010, 05:18 PM   #6521
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No, SY, only a preprint vetted by a Stanford professor, and of course the patent of the test procedure. I warned Ron already that publishing in the JAES will be almost impossible, but he is still hopeful. His measurements look real enough.
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Old 7th November 2010, 05:59 PM   #6522
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Quote:
Originally Posted by 1audio View Post
Obviously Scott objects to the language used. But is there substance underneath the less than academically perfect description? Can anyone explain in clear terms what Ron's position, arguments and measurements are?
I think Scott is correct to insist on proper descriptions - sloppy
naming creates a lot of confusion.

As far as I can see the patent is describing phase modulation
in the same way that the classic IM test involves amplitude
modulation. Phase modulation appears to be one of the
elements in the aforementioned "grouping mechanisms", but
I suspect that your modern amplifier is going to exhibit this
at the same low levels as amplitude modulation.

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Old 7th November 2010, 06:05 PM   #6523
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OK, so maybe Bob can make a comment. Sample the output of the amplifier at 24/192 and separate the real and imaginary components mathematically and extract the AIM and PIM. I read the patent and there was nothing there that did not have a digital analog.

Wow and flutter (in their normal context) are typically non-harmonicly related to the signal frequencies, this inexactitude implies non-physical results.
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Last edited by scott wurcer; 7th November 2010 at 06:16 PM.
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Old 7th November 2010, 06:30 PM   #6524
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Was is an actual paper or a preprint?
You're right, I forgot. L & V have not had a go at it yet.
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Old 7th November 2010, 06:44 PM   #6525
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You have to forgive my colleague, Ron Quan. He is just a working audio-video engineer located in Silicon Valley, who can still hear differences in audio equipment, and has invested his time and effort to do a paper for the AES, even knowing in advance that many will not appreciate it. He worked with me, BEFORE L & V took over the AES, keeping out radical elements pushing such measurements. I apparently poisoned his mind toward whatever works, rather than precise definitions. I would have not put 'Wow and Flutter' in as a perfect description of what he is measuring, but you must also understand that he also worked at Ampex, when magnetic tape was popular, before digital completely took over, and wow and flutter are common measurements that we made working at such companies. A loose definition of flutter is really dynamic FM modulation. Anyone here can look it up. I hope that some do.
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Old 8th November 2010, 12:20 AM   #6526
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Originally Posted by scott wurcer View Post
You're right, I forgot. L & V have not had a go at it yet.
At least everyone doesn't have to travel to Waterloo.

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Old 8th November 2010, 12:59 AM   #6527
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Yes, they will make sure that nothing gets though.
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Old 8th November 2010, 05:48 AM   #6528
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Quote:
Originally Posted by scott wurcer View Post
OK, so maybe Bob can make a comment. Sample the output of the amplifier at 24/192 and separate the real and imaginary components mathematically and extract the AIM and PIM. I read the patent and there was nothing there that did not have a digital analog.

Wow and flutter (in their normal context) are typically non-harmonicly related to the signal frequencies, this inexactitude implies non-physical results.
I heard several comments at the AES to the effect that what he measured was real enough, but that it did not disclose non-linearities that were not known already and that could be measured by more traditional means. In other words a very ingenius and valuable way of providing another perspective at known shortcomings.

I'm sure that Bob C can comment more to the point, but as far as I know he's in a red-eye en route to NJ at this moment.

John, what's your take on it?

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Old 8th November 2010, 05:56 PM   #6529
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It has been my firm 'belief' for the last 30 years, since real (in my opinion) effort has been made to find the underlying differences in audio electronic design that make some designs sound 'better' than others.
The first effort by Matti Otala, who was prompted by Mitch Cotter (a known FM designer) to put PIM or FM distortion or differential phase, as the most likely cause, was suppressed from publication in the JAES. Then it was looked at by Cordell and discounted as not being very important.
The subject sat in abeyance for about 15 years, until Barrie Gilbert looked more fully into the problems with op amps. Then, he gave a masterful QUANTITATIVE ANALYSIS of an idealized version of an op amp commonly used in some fashion by literally thousands of designs for the last 40 years. Here was the 'smoking gun'.
As usual, it was dismissed by many.
Then, Mitch Cotter told me what he had noted in Matti's and my preprint on TIM, first given in 1976 at the NY AES. This was the famous 741 TIM(30) measurement with 5V peak-to-peak output, and 30KHz -3dB rolloff. Several UNDEFINED IM looking tones that had no easy definition in terms of IM itself, apparently were FM sidebands, instead. This was noted more than 30 years ago by Mitch Cotter. He had told Matti Otala, but he had not informed me until about 1 year ago, or so. Looking at the data, and noting this insight about the FM sidebands mixed with the traditional IM on this thread, brought the same criticisms that Ron Quan is about to experience from his looking for FM or differential phase distortion more directly, through using video techniques.
For some reason, people do not appreciate the existence of FM byproducts, and usually claim them to be 'exotic' IM byproducts, if at all possible.
I do not wish, at this time, to parse with the definitions or device selection that Ron Quan used. However, the measurements are backed up by both test procedure and by mathematical calculations. Anyone seriously interested, can duplicate his tests and expand even further, as it is clearly stated how to do it in his paper and in his patent # US 7,550,977 B2.
I am MOST interested in why op amps, in particular, sound different in my experience, and this is the most likely reason. This testing might also give a more concrete reason why open loop bandwidth seems to make a difference, at least to me. We shall see.

Last edited by john curl; 8th November 2010 at 06:11 PM.
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Old 8th November 2010, 06:40 PM   #6530
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Originally Posted by john curl View Post
It has been my firm 'belief' for the last 30 years, since real (in my opinion) effort has been made to find the underlying differences in audio electronic design that make some designs sound 'better' than others.[snip].
I think what would be of interest whether this new measuring method found artifacts that we were not aware of. That would really be something!
Do you believe that is the case?

As you said, the existence of FM modulation and other stuff mentioned by you was established some 30 years ago. Is Quan looking at the same phenomenon with a different pair of glasses, or did he see something new?

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Last edited by jan.didden; 8th November 2010 at 06:44 PM.
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