Will digital CD audio differ from player to player? (1 Viewer)

[Lee Scoggins]

But my main point is this: any slight change in the timbre of the audio due to sub-nanosecond jitter would be overwhelmed by timbre-changes caused by a 1-degree difference in the temperature, the presence of a small animal in the room, the movement of dust on your speaker, etc. Night and Day differences should be out of the question, as far as the objective world is concerned anyways. Inside the subjective world, any number of things can affect the perception of sound.

See this is where you whole logic chain breaks down. You are assuming that the human brain is incapable of judging very small changes in time-domain distortion. Using scientific studies within the above mentioned AES paper, we know this is indeed true that the brain can get to nanasecond audibility...why would picosecond variability not be possible?

I reject the analysis of temperature and dust as these would affect only certain frequencies or locations at most, if even possible. But distortion in the timing of an audio signal - that's a biggie!

One of the reasons I argue strongly on some points is that I know they are true because I hear them in the studio. I hear differences between 200 ps and 20 ps when I add an external Master Clock. My friends who work with me also clearly hear the difference. And it is why many recording engineers feel strongly that jitter control is a critical step in capturing better sound.

 

[Lee Scoggins]

I am not prepared to believe (it would take a fair amount of evidence) that the timing of the 1s and 0s make up the difference.

Seems like you already made up your mind. I won't try to confuse you with the facts. Would it not be better to say "it does not seem likely this could happen, but I will try to devise a test of low and high jitter transports and listen for myself on a good system."?

By the way, do you ever wonder why companies like Lucid Audio do a brisk business in external master clocks?

They only affect the timing...why would anyone buy them if they thought jitter was some fringe idea???

Stop by and see me next time you are in Atlanta and I will show you the difference in sonics. On classical works the difference in the string sections is amazing.

 

[Jagan Seshadri]

Jun-Dai said

But my main point is this: any slight change in the timbre of the audio due to sub-nanosecond jitter would be overwhelmed by timbre-changes caused by a 1-degree difference in the temperature, the presence of a small animal in the room, the movement of dust on your speaker, etc.

So true. I still think that playback room acoustics trump most of these small problems. I suspect the shape of one's outer ears would affect the stereo soundstage too, as would having a shaggy hairstyle versus a crew-cut.

I still don't follow how on earth jitter could be introduced in the pressing phase of digital discs. Error-correction would clean up any misfiring 'pits', and the works is buffered on playback. These jitter arguments may have been true before buffered playback.

Of course, a lot of the enjoyment of this hobby is in trying to get equipment that sounds and works amazingly well, but to berate (or dismiss) science and engineers and double-blind testing is to bite the hand that feeds you.

-JNS

 

[Asim]

Ahhh...this gets even better.

First of all, i agree, Jun-Dai...you had several good points!

As for Lee....

to berate (or dismiss) science and engineers and double-blind testing is to bite the hand that feeds you.

Now that hits the nail on the spot, Jagan!

ahhh...HTF is such a nice welcome distraction from analyzing data!

- asim

 

[Jun-Dai Bates]

By the way, do you ever wonder why companies like Lucid Audio do a brisk business in external master clocks?

I am never surprised when corporations persue unscientific/pseudoscientific research. It's standard practice, and there are even companies whose whole business is based on the public perception of something being scientific but is in fact anything but. Consider that there is a whole cottage industry behind the manufacturing of gold audiophile CDs.

Audiophiles are connoisseurs, and like connoisseurs of any sort, they live half in the world of science, and the other half in the world of pseudoscience. A good part of what audiophile companies sell is predicated on hypotheses whose proof is beyond the means of the scientific community.

The idea of jitter goes against common sense, which explains the reaction that it produces in a lot of people. In science, things that go against common sense, or even worse, against established theories, require much more effort to prove, and rightly so. Jitter is one of those cases, and I think that most of us here require a theoretical proof (or at least a logical series of explanations) that will convince us that the effects of jitter can be greater than other circumstances, such as air temperature (which has a significant effect on audio waves--an increase in temperature of 1 degree celcius increases the speed of sound by 1.5 miles an hour), or the existence of dust on a speaker (this will have a tremendous effect on the sound of a speaker, at least when we're talking about pico-anything--consider that light in a vacuum travels .0003 meters in a picosecond), or the presence of a cat in the room (again, a tremendous effect on the acoustics of the room). If we can't have a theoretical proof, then we want a reliable paper on the results of a series of double-blind tests. If we can't have reliable double-blind test data, then we at least need a plausible explanation. Lee has provided us with this, to some extent, but there are plausibility issues that haven't been addressed, and without that there is a limit to the amount of convincing that is going to be done.

As for corporations, a lot of the people that run them use fortune-telling to guide important decisions. Scientists rarely determine the course that companies take.

 

[Lee Scoggins]

Of course, a lot of the enjoyment of this hobby is in trying to get equipment that sounds and works amazingly well, but to berate (or dismiss) science and engineers and double-blind testing is to bite the hand that feeds you.

This is a mischaracterization of my comments.

First, I have never dismissed science. I think it is very valuable but has real limitations in audio.

Second, I have only berated engineers in the sense that many instinctively feel (1) that only objective metrics matter and (2) software engineers are more schooled in digital conversions than those associated with timing differences.

Third, I do feel that DBTs have severe limitations on subtle sonic differences and in some cases substantial differences. They are complex to set up, difficult to implement, and this is borne out by the relatively few DBTs in the literature on audio events.

 

[Lee Scoggins]

As for corporations, a lot of the people that run them use fortune-telling to guide important decisions. Scientists rarely determine the course that companies take.

I work with CEOs and CFOs primarily in my software company since I measure buiness risk and I must say this is not an accurate statement based on my 14 years in business. Most company decisions are based on strategic analysis set by MBAs and are often backed up by data collection and numerical analysis of different outcomes.

 

[Lee Scoggins]

Jun-Dai,

Here is a copy of my earlier comments...in case you missed them (from the second page). The AES paper was from Eric Benjamin and Benjamin Gannon:
------------------------------------------
Here is an excellent and free paper on Jitter Theory from the Audio Precision website:

http://audioprecision.com/publicati...notes/index.htm

(register and download #23 - Jitter Theory, an excellent overview)

In the latter pages, there is a paper referenced that suggests the limit of audibility is around 10 nanoseconds for 17khz tone. The author cautions that recent work extends this lower limit even further.

I am attempting to get more recent research but at least we have some academic theory and research for jitter audibility that is completely unrelated to product sales.

The most recent AES discussion I attended suggested that 10-20 picoseconds is current limit.
---------------------------------

Citation of AES Paper:

Theoretical and Audible Effects of Jitter on Digital Audio Quality
Many digital audio systems now use some form of self-clocked digital interface for audio delivery. With the advent of new digital audio systems that use IEC 61937 to convey non-linearly coded audio, the total number of devices using the IEC 60958 interface has substantially increased. The digital interface may contain jitter that translates to distortion in the audio at the point of conversion back to the analog domain. Sources of digital audio, the digital interface, the mechanisms by which errors are introduced, and the effect on DACs are examined
Preprint Number: 4826 Convention: 105 1998-09
Author: Eric Benjamin
Author: Benjamin Gannon


Now we can at least establish a scientific floor under our discussion...

 

[Lee Scoggins]

What, no rebuttal to my scientific paper finding jitter audible?

I was hoping for more discussion.

 

[Lee Scoggins]

I posted a thread with a new paper with a 20 ps figure and a new test we did today in Atlanta over in the Music section.

 

[Asim]

Not Found
The requested URL /publicati...notes/index.htm was not found on this server.

Apache/1.3.26 Server at www.audioprecision.com Port 80



Perhaps they found errors in it and removed it?

 

[Lee Scoggins]

Perhaps they found errors in it and removed it?

Not at all, they already published it. The server must just be down. I have the Jitter Theory PDF so I can email it to you.

Try this one from my music section post...

By Julian Dunn of Nanophon:

http://www.nanophon.com/audio/jitter92.pdf

See also the whole thread at:

http://www.hometheaterforum.com/htfo...hreadid=125572

 

[Lee Scoggins]

Asim...Jun Dai...

You out there?

 

[Jun-Dai Bates]

I'm reading the documentation. Things have gotten a little busy at work, so I have less time to ponder these matters than I did last week.

 

[Lee Scoggins]

That's Cool. Let me know when things slow down for you.

 

[Asim]

Sorry...do not have time to read them at the moment...i have a poster i am getting ready for a meeting this weekend and much data analysis needs to be done. Anyhow, i will read and comment when i get back. tell me why i am getting a Ph.D. again?

- asim...MuDder PhuDer

 

[Lee Scoggins]

Hang in there Asim.

The PHD will be worth it. One of my business partners has one and it does add value.

 

[Asim]

Lee,
I am getting my Ph.D. only for personal (ego) reasons.
Now, the M.D., on the other hand, will be for the value-
added benefit, as well as to finance my hobbies.
Of course, i do enjoy helping people first and foremost .

 

[ManW_TheUncool]

I am getting my Ph.D. only for personal (ego) reasons.
Now, the M.D., on the other hand

That's just sick, IMHO.

_Man_

 

[Lee Scoggins]

Now, the M.D., on the other hand, will be for the value-

Sometimes a PHD is more valuable. I think applied math, for instance, beats a medical degree (in the traditional physician sense) any day of the week, at least economically.

I should know - my whole family is doctors going back to the 1800s.

Getting both MD and PHD - that's a long road IMHO.