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Author Topic: Is PCM a Tremolo Machine ?  (Read 26644 times)

Chuck

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Is PCM a Tremolo Machine ?
« on: June 14, 2004, 12:12:40 AM »

Hi,

what I would like to offer for discernment does not fit into this box, so I have put it on my site:

http://www.mother-of-tone.com/cd.htm

Charles Smile
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Johnny B

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Re: Is PCM a Tremolo Machine ?
« Reply #1 on: June 14, 2004, 02:31:41 PM »

Thanks Charles, interesting site and link.

Maybe you'd like to put a link to the atricle on the 192K thread, I dunno.
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Nika Aldrich

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Re: Is PCM a Tremolo Machine ?
« Reply #2 on: June 14, 2004, 03:52:43 PM »

I am very leary about getting involved in this thread online as the nature of this discussion might get into a mathematics area that is outside of the scope of the typical discussion on a music related website thread.

There are several problems with this paper, all of which can be wrapped up into the quote of Shannon's theorem.  The conclusion is drawn in the paper that Shannon's theorem requires an infinite sum and therefore renders the reconstruction process incomplete and inaccurate, thereby requiring higher sample frequencies.

The problem with this is that an infinite sum is only required if we sample at only double the highest frequency in the system. As you write:

Well it means at least one thing:

If we sample as slow as twice the highest frequency, in the real world, we never - and I say never - get back to the original signal!"


Of course this is correct, but you have left the crucial detail out that if we sample 1/infinity greater than this frequency then reconstruction is perfect with finite time systems.   If we sample higher than double the highest frequency present then we no longer require an infinite sum in the reconstruction process and Shannon and Nyquist both work properly - in other words, higher sample frequencies are not required if we simply sample at greater than twice the highest frequency present.

We can see in Shannon's theorem that his theorem deals with infinite time.  Shortening that to a finite amount of time no longer requires infinite sampling to create accuracy.  Try it.  I guarantee it works.

Also, the quote ascribed to Nyquist is not the Nyquist theorem - I'm sure it is something he wrote, but it is not the crux of his famed paper, "Certain Topics on Telegraph Transmission Theory."

Charles, I find your paper very frustrating.  It is clearly very erroneous and allows the populous that reads it to draw incorrect conclusions about the nature of digital audio reconstruction.  I think you are doing a great disservice to the market at large by publishing such information.  I think you should pull the paper down and rewrite it factually and then re-post it.  Your writing style is good and you are effective at getting a point across, but this point is simply false.  It is simply incorrect that a higher FS system can reconstruct a 14kHz system more accurately than a base rate system, and it is simply inaccurate that modulation occurs on reconstruction of a properly sampled waveform.  That is simply, absolutely erroneous and it is totally discouraging to see you peddleing such bunk.

Remember that Shannon only works either with infinite time at 2N or less than infinite time at >2N, and that ANY amount of time less than infinite is acceptable and ANY sample frequency greater than 2N works.

Nika.
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Paul Frindle

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Re: Is PCM a Tremolo Machine ?
« Reply #3 on: June 14, 2004, 07:43:40 PM »

Nika Aldrich wrote on Mon, 14 June 2004 20:52



Charles, I find your paper very frustrating.  It is clearly very erroneous and allows the populous that reads it to draw incorrect conclusions about the nature of digital audio reconstruction.  I think you are doing a great disservice to the market at large by publishing such information.  I think you should pull the paper down and rewrite it factually and then re-post it.  Your writing style is good and you are effective at getting a point across, but this point is simply false.  It is simply incorrect that a higher FS system can reconstruct a 14kHz system more accurately than a base rate system, and it is simply inaccurate that modulation occurs on reconstruction of a properly sampled waveform.  That is simply, absolutely erroneous and it is totally discouraging to see you peddleing such bunk.

Nika.


Of course - I agree. The conclusions suggested on the mentioned text are totally and completely false and damagingly misleading to anyone who seeks to understand the sampling mechanism. It makes absolutely no sense at all - and it pains me deeply to have to say such on this forum Rolling Eyes  Perhaps a read of the old 96KHz thread from George's previous forum would not go amiss?
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Zoesch

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Re: Is PCM a Tremolo Machine ?
« Reply #4 on: June 14, 2004, 09:10:33 PM »

I don't disagree that the conclusions are wrong and misleading, but I can't help but be amused with the amount of aliasing he's getting.

(Although he does mention something that is theoretically correct but practically (And easily provable) wrong)
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JGreenslade

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Re: Is PCM a Tremolo Machine ?
« Reply #5 on: June 15, 2004, 08:47:05 AM »

Charles's site is an intriguing source of information, check this link and see what you think:

http://www.altmann.haan.de/tubeolator/default.htm

The BYOB amp, is it really 700 Euros??


Justin
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Chuck

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Re: Is PCM a Tremolo Machine ?
« Reply #6 on: June 15, 2004, 09:30:36 AM »

Nika Aldrich wrote on Mon, 14 June 2004 21:52


Charles, I find your paper very frustrating.  It is clearly very erroneous and allows the populous that reads it to draw incorrect conclusions about the nature of digital audio reconstruction.

Nika.


Hi Nika,

thank you for the many words. I have shown 21 kHz and 22kHz measurements of the DF1704 high-performance digital filter that absolutely underlign my explanations.

If anyone out there thinks he has better DA equipment, please feel free to step forward and prove that you can perfectly reconstruct let's say a 21kHz sine wave with a 44.1 sample rate.

I am not repeating things I don't understand. I am doing research, and until now you got not a single point against my evidence. My information is not misleading. It is information.

Charles Smile
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Chuck

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Re: Is PCM a Tremolo Machine ?
« Reply #7 on: June 15, 2004, 09:46:14 AM »

Zoesch wrote on Tue, 15 June 2004 03:10

I don't disagree that the conclusions are wrong and misleading, but I can't help but be amused with the amount of aliasing he's getting.

(Although he does mention something that is theoretically correct but practically (And easily provable) wrong)


Hi Zoesch,

there is no alias involved. In the diagrams I show the accurate samples of pure sine-waves with frequencies well below Fs/2.

It just looks strange to you, because you have never looked at it. You can check it out with almost any sound-software.

Charles Smile
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maarvold

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Re: Is PCM a Tremolo Machine ?
« Reply #8 on: June 15, 2004, 11:06:05 AM »

Ironic that, presumably, most of us put up with a 24 FPS frame rate in theaters, a roughly 30 FPS A/B (interlaced) electron beam scan on a tv screen and that wacky film to video frame rate conversion; if I remember correctly, it's 4 film frames = 5 video frames and the methodology (one odd line field + one even line field--called interlacing--equals 1 video frame) is:

AA  AB  BC  CD  DD

Talk about a tremelo machine...

But then, maybe that leads to the essence of the problem:
When you see the whole picture in one shot (like 1 film frame) an Fs of 24 is adequate, but with music, I don't think there is a system out there that can give the whole 'picture' in 1 shot.  Maybe we're all completely barking up the wrong tree.  Or maybe it's true, and prophetic, that "one picture is worth a thousand [digital] words".  
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davidc

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Re: Is PCM a Tremolo Machine ?
« Reply #9 on: June 15, 2004, 11:19:41 AM »

maarvold wrote on Tue, 15 June 2004 16:06

Ironic that, presumably, most of us put up with a 24 FPS frame rate in theaters, a roughly 30 FPS A/B (interlaced) electron beam scan on a tv screen and that wacky film to video frame rate conversion; if I remember correctly, it's 4 film frames = 5 video frames and the methodology (one odd line field + one even line field--called interlacing--equals 1 video frame) is:

AA  AB  BC  CD  DD

Talk about a tremelo machine...

But then, maybe that leads to the essence of the problem:
When you see the whole picture in one shot (like 1 film frame) an Fs of 24 is adequate, but with music, I don't think there is a system out there that can give the whole 'picture' in 1 shot.  Maybe we're all completely barking up the wrong tree.  Or maybe it's true, and prophetic, that "one picture is worth a thousand [digital] words".  


Well actually 24 frames is not adequate. Whenever I go to the cinema I am all too aware of picture judder.

Best Regards

David C
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Nika Aldrich

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Re: Is PCM a Tremolo Machine ?
« Reply #10 on: June 15, 2004, 12:16:07 PM »

Chuck wrote on Tue, 15 June 2004 14:30


Hi Nika,

thank you for the many words. I have shown 21 kHz and 22kHz measurements of the DF1704 high-performance digital filter that absolutely underlign my explanations.


Either this converter has poor on band filtering or you are not showing the results of this converter after proper post-processing after the D/A.  You have to filter the D/A after its conversion.  You can't take the output of the chip with no further anti-image filtering in the analog domain and say that digital audio is defective!!  After you do this it will look very different - or else the onboard downsampling filtering is pathetic.  

Quote:

If anyone out there thinks he has better DA equipment, please feel free to step forward and prove that you can perfectly reconstruct let's say a 21kHz sine wave with a 44.1 sample rate.


Why?

Quote:

...and until now you got not a single point against my evidence


Yes.  Your diagrams have not undergone complete reconstruction.  You are either sampling the output of an improperly designed D/A circuit or you are doing this in software that does an inadequate job of reconstruction filtering on its graphic display.

On your 14kHz waveform you indicate that there is amplitude modulation.  This is completely erroneous and only a result of poor reconstruction filtering on your outputs or poor software graphics.  Have you run a properly converted and reconstructed 14kHz sine wave out of your system and into an oscilloscope?  Funny, eh?  No AM distortion.

You write, "...its volume has been modulated by a lower frequency."  This is absolutely false.  You are indicating here that you do not follow the manufacturers instructions on post-chip filtering or you really do not know what you are doing.  If you are getting these results then you are using bad equipment - it's as simple as that.  And if you designed that equipment then you have a lot more to learn.

You mis-represented Nyquist and mis-applied Shannon.  You determine that Shannon must be inapplicable simply because you insist on sampling at 2N and never explain how Shannon actually DOES work at >2N.

You write, "...the true meaning of the sampling theorem.  It means you never get back to the original signal, in finite time."  Which is complete garbage and you know it.  Start with a finite time signal.  Sample at >2N and you CAN reconstruct it in finite time.



I'm very disappointed at how you are presenting this.  It is absolute and complete bunk and if you don't know it you need to do some homework before you start throwing misleading papers out on the market, and if you do know it then shame on you.

Nika.

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Chuck

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Re: Is PCM a Tremolo Machine ?
« Reply #11 on: June 15, 2004, 02:21:01 PM »

Hey Nika,,

you seem to have no experience with DA converters and digital audio in general.

If you are able to operate a scope, why don't you grab your favorite DA converter and take a look yourself before writing so much BS ?

I have used one of the best reconstruction filters available, the DF1704. You think you can up with something better. Okay, lets see it.

And even if you get that perfect reconstruction, it just shows, that you (like many others) don't know that Shannon's interpolation formula is for stationary signals. The ringing on the impulse response of any reconstruction filter is a perfect evidence of this fact.

This has nothing to do with music, as music is not a stationary signal.

And therefore oversampling filters are not used anymore by many music lovers, audiophiles and sound researchers on this planet.

I don't speak againg Nyquist, nor against Shannon. They were both perfectly right in what they said. The problem is that their exact words were distorted over the time.

And You keep on distorting them.

Charles Smile
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Nika Aldrich

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Re: Is PCM a Tremolo Machine ?
« Reply #12 on: June 15, 2004, 03:09:49 PM »

Chuck wrote on Tue, 15 June 2004 19:21

I have used one of the best reconstruction filters available, the DF1704. You think you can up with something better. Okay, lets see it.


What are you using after the output of the 1704???  

Quote:

And even if you get that perfect reconstruction, it just shows, that you (like many others) don't know that Shannon's interpolation formula is for stationary signals.


This is absolutely wrong.  Shannon's formula was for any waveform that has no frequency content above N.  That means ANY waveform, not just stationary or cyclical waveforms.  Read the theorem again.  It does not qualify the waveform.  It says that any waveform with a fixed frequency content can be represented with a specific sample rate.  You are putting words in that don't exist because you have yet to do the math to realize that it actually works.  Do a DFT analysis of the sampled waveform and compare it to an FFT of the original waveform.

Quote:

The ringing on the impulse response of any reconstruction filter is a perfect evidence of this fact.


How in the world do you draw this conclusion?  The ringing is inherent in any filter because it has to dissipate out high frequency transients over longer periods of time.  It is not perfect evidence at all that Shannon is somehow broken or regulated to cyclical waveforms at all.  

Quote:

And therefore oversampling filters are not used anymore by many music lovers, audiophiles and sound researchers on this planet.


What on earth are you talking about?  If you don't filter you are breaking Nyquist/Shannon intentionally and creating a waveform whose frequency content is "illegal" according to the theorem.  Why would we possibly concern ourselves with systems that are intentionally broken and do not reconstruct the waveform properly?  This is the most ludicrous theory I've heard yet.  No wonder you want higher FS - you're using a system that is intentionally broken and selling it as though it works?  This is simply amazing.

Quote:

I don't speak againg Nyquist, nor against Shannon. They were both perfectly right in what they said. The problem is that their exact words were distorted over the time.


Do tell.  Find the phrase in Shannon that says that it has to be a stationary waveform and we'll see who, exactly, is distorting the words.

Chuck, I'm completely amazed at your lack of understanding and that you supposedly "make" equipment and sell it to people.

Nika.
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Eliott James

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Re: Is PCM a Tremolo Machine ?
« Reply #13 on: June 15, 2004, 04:03:24 PM »

I take no sides with math... let's play in the real world of shape, form and perception!

Easy enouph to prove or disprove - Chuck, build a converter based on your designs, record music digitally, send back thru a converter of your design, use the BYOB amp and spruce speakers if you like -  how does it sound?

Of course, we'll have to hear this to judge.
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Zoesch

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Re: Is PCM a Tremolo Machine ?
« Reply #14 on: June 15, 2004, 06:00:44 PM »

Chuck wrote on Tue, 15 June 2004 23:46

there is no alias involved. In the diagrams I show the accurate samples of pure sine-waves with frequencies well below Fs/2.


Oh yes there is, just because you are below Fs/2 doesn't mean you won't get any aliasing, that's a sign of a really bad designed converter (I can point you where you are generating your aliases from here)

Hint: Your A/D

Quote:


It just looks strange to you, because you have never looked at it. You can check it out with almost any sound-software.



You can check it with an oscilloscope and that's a lot more fun, I've seen this over and over and over and over again, so yeah, you want me to tell you exactly where your problems are? (For a small and not so unreasonable sum of money of course)

Of course, we could talk about other coding mechanisms and everyobody's half assed understanding of what Nyquist wrote, but that should be a thread on its own.
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