Jitter test

Julf

New Member
Nov 27, 2011
613
0
0
Amsterdam, The Netherlands
Sure, I know the theory but in practise there still seems to be audible differences between high & low jitter sources when using such players. So, perhaps, as DJ said it ain't just jitter that is at the heart of the matter - maybe the 1/f noise is varying - maybe it's noise modulation, ala Opus111, maybe it's something else?

Right - and that is the discussion we should be having. Not a blind "jitter is bad, and everything causes jitter", but "what kind of jitter, and how much, is audible, and under what conditions?"

David Kessner has a good perspective on jitter in A Pragmatic Approach To Jitter In Digital Audio.
 

jkeny

Industry Expert, Member Sponsor
Feb 9, 2012
3,374
42
383
Ireland
............ Not perfect, but good enough for my purposes.

And your purpose was? Maybe you can say what you think is not perfect about your toy set-up & why it might not be up to the job of proving/dissproving your thesis? Also how it might be any better to my toy DBT set-up and whether the conflicting results between the two (I presume you have not heard any differences between different software playback) have any significance whatsoever?
 

jkeny

Industry Expert, Member Sponsor
Feb 9, 2012
3,374
42
383
Ireland
Right - and that is the discussion we should be having. Not a blind "jitter is bad, and everything causes jitter", but "what kind of jitter, and how much, is audible, and under what conditions?"

David Kessner has a good perspective on jitter in A Pragmatic Approach To Jitter In Digital Audio.
You think that article is a good perspective? Give me a break - from his conclusion
Before worrying about 2 ns of jitter, you need to remove the other sources of “jitter” in your listening room. To do this: Stop breathing, stop your heart, cool your body down to room temperature, seal the room from any outside air, turn off that hot Class-A amp, and disconnect your speakers. That’s all!

In short: anybody who claims to be able to hear 2 ns of jitter is either a mistaken, a liar, or a zombie. I’ll assume the best by assuming that they are a zombie!
 

Julf

New Member
Nov 27, 2011
613
0
0
Amsterdam, The Netherlands
And your purpose was? Maybe you can say what you think is not perfect about your toy set-up & why it might not be up to the job of proving/dissproving your thesis? Also how it might be any better to my toy DBT set-up and whether the conflicting results between the two (I presume you have not heard any differences between different software playback) have any significance whatsoever?

Well, it was more than enough for my purposes, because I had no thesis to prove. It was enough to convince me, personally, that there was no audible difference. It is not a result that can be generalized beyond that. What is needed is proper scientific research, and fortunately there is a fair bit of that going on. Looking forward to some interesting EBU and AES papers (I know of at least one pretty serious effort that should be able to publish something this year).
 

opus111

Banned
Feb 10, 2012
1,286
3
0
Hangzhou, China
You think that article is a good perspective? Give me a break - from his conclusion..

You must have a lot of patience to get that far - I only got to here:

MCLK is the only thing that matters when it comes to jitter.

...and realized that jitter can't be any kind of problem at all for me as my DAC doesn't have MCLK.
 

Julf

New Member
Nov 27, 2011
613
0
0
Amsterdam, The Netherlands
You think that article is a good perspective? Give me a break - from his conclusion

And do you have verified research showing 2 ns of jitter is audible?

Until now I hadn't taken notice of your signature (as I follow this forum over email, and the emails don't show the signature). I now realize your views might be driven by commercial interests. Fair enough.
 

Julf

New Member
Nov 27, 2011
613
0
0
Amsterdam, The Netherlands
...and realized that jitter can't be any kind of problem at all for me as my DAC doesn't have MCLK.

Ah, yes, I guess for literal readers he should have written "MCLK or whatever equivalent your DAC uses to control the conversion sample rate".
 

jkeny

Industry Expert, Member Sponsor
Feb 9, 2012
3,374
42
383
Ireland
And do you have verified research showing 2 ns of jitter is audible?

Until now I hadn't taken notice of your signature (as I follow this forum over email, and the emails don't show the signature). I now realize your views might be driven by commercial interests. Fair enough.

And your views are well known from the many forums you inhabit but my views are driven from my experience which I have posted before my commercial activities. Fair enough?
 

Julf

New Member
Nov 27, 2011
613
0
0
Amsterdam, The Netherlands
And your views are well known from the many forums you inhabit but my views are driven from my experience which I have posted before my commercial activities. Fair enough?

Absolutely. And I am not saying a commercial interest is a bad thing per se - apart from pure academic researchers, most real experts in the field are employed by companies with some commercial interest. It is just an aspect to be aware of.
 

microstrip

VIP/Donor
May 30, 2010
20,806
4,698
2,790
Portugal
People have not being able to correlate the "sound" of a simple device - a CD transport supplying the SPDIF signal to a high quality DAC - with jitter or any other technical argument. They found that bit content was 100% similar, but could not find a plausible explanation for the different sounding transports, and relied on jitter in a vague way to explain it.

Now we have a very complicated system - a computer not optimized for audio, with many variables and its interface. If we were not able to solve the simple problem, should we believe we will have the solutions for the complicated one soon? BTW, I am addressing sound quality, not mathematical theorems.
 

Julf

New Member
Nov 27, 2011
613
0
0
Amsterdam, The Netherlands
People have not being able to correlate the "sound" of a simple device - a CD transport supplying the SPDIF signal to a high quality DAC - with jitter or any other technical argument. They found that bit content was 100% similar, but could not find a plausible explanation for the different sounding transports, and relied on jitter in a vague way to explain it.

I would be interested in seeing any results of proper controlled studies where people have been able to a) verify that the data content (bits) are indeed 100% the same, and b) still can tell differences in a controlled, double-blind test.

Now we have a very complicated system - a computer not optimized for audio, with many variables and its interface. If we were not able to solve the simple problem, should we believe we will have the solutions for the complicated one soon? BTW, I am addressing sound quality, not mathematical theorems.

It doesn't really matter if the system is simple or complicated - any errors will show up in the output, and be ultimately measurable.

When we measure noise, distortion, and deviations from a flat frequency response, we don't need to understand exactly what causes the errors - but we can still measure them.
 

microstrip

VIP/Donor
May 30, 2010
20,806
4,698
2,790
Portugal
I would be interested in seeing any results of proper controlled studies where people have been able to a) verify that the data content (bits) are indeed 100% the same, and b) still can tell differences in a controlled, double-blind test.

It doesn't really matter if the system is simple or complicated - any errors will show up in the output, and be ultimately measurable.

When we measure noise, distortion, and deviations from a flat frequency response, we don't need to understand exactly what causes the errors - but we can still measure them.

The data content tests were carried and published decades ago by several magazines. As many others, I also modified a Philips and a Sony CD player putting counters in the several error pins looking for error statistics, as published by hobby magazines such as Elektor, and found that the rate of errors was absolutely minimal. The myth of the errors - at that time one of the most important parameter of CD performance was the larger gap that could be read without audible distrotion - soon disappeared.

My point is that carrying measurements without trying to establish an audible correlation is not my interest. Happily yours seems different.
 

Julf

New Member
Nov 27, 2011
613
0
0
Amsterdam, The Netherlands
The data content tests were carried and published decades ago by several magazines.

Any pointers?

The myth of the errors - at that time one of the most important parameter of CD performance was the larger gap that could be read without audible distrotion - soon disappeared.

I am not claiming there were errors - I am questioning the audible differences.

My point is that carrying measurements without trying to establish an audible correlation is not my interest. Happily yours seems different.

Not at all. My concern is exactly with establishing a correlation between audible observations and measurements.
 

Soundproof

New Member
Jan 13, 2012
429
1
0
Oslo, Norway
Some years ago, TAS got a letter from a reader. "Quoting" from memory now, but the letter was in response to a reviewer hearing a significant difference between two components that had a jitter difference of 7 picoseconds. (15 and 8)
The reader suggested the following, to understand what 7 picoseconds meant:

Place issues of TAS in a belt around the Equator, the spine up, tightly packed together, until you had a belt running right around the planet.
He'd calculated the average thickness of an issue (71 sheets), and reached the conclusion that four picoseconds would correspond to three pages in one issue in that belt spanning the globe.
(The TAS-belt representing one second, and consisting of 4.400.000.000 issues).

And that was when jitter was measured in picoseconds. Jump to nano, and I guess the jitter would be represented by a period on a page. It ain't that much of a problem no more, maybe?
 

Julf

New Member
Nov 27, 2011
613
0
0
Amsterdam, The Netherlands
And that was when jitter was measured in picoseconds. Jump to nano, and I guess the jitter would be represented by a period on a page. It ain't that much of a problem no more, maybe?

Well, 1 ns = 1000 ps. But in any case, to provide another perspective, sound moves 0.3 ?m (3/10000 of a mm) in one nanosecond (that is 1/100000 of an inch for citizens of the US, Burma and Liberia). That is less than 1/300th of the thickness of a human hair - and in one picosecond, sound travels 1/1000 of that distance.
 

Julf

New Member
Nov 27, 2011
613
0
0
Amsterdam, The Netherlands
-- But all of this is relative; the real application in audio (master clock and all), and its listening results by different people is our true main concern.

Absolutely. Listening results by different people, under controlled, reproducible conditions.
 

jkeny

Industry Expert, Member Sponsor
Feb 9, 2012
3,374
42
383
Ireland
This simplistic discussion of jitter & simplistic examples (started in that article with the so called good perspective) are so misleading as to be verging on disingenuous. Firstly we all know that a single number for jitter is misleading but more importantly the category of jitter is the most important qualification - random or correlated. The examples here are ignoring the possible effects of correlated jitter varying with the signal & how that might effect audio reproduction. I don't wish to get into a discussion of this - it has already been covered by Amir here I would suggest that all read it as an antidote to that article liinked to by Julf
 

About us

  • What’s Best Forum is THE forum for high end audio, product reviews, advice and sharing experiences on the best of everything else. This is THE place where audiophiles and audio companies discuss vintage, contemporary and new audio products, music servers, music streamers, computer audio, digital-to-analog converters, turntables, phono stages, cartridges, reel-to-reel tape machines, speakers, headphones and tube and solid-state amplification. Founded in 2010 What’s Best Forum invites intelligent and courteous people of all interests and backgrounds to describe and discuss the best of everything. From beginners to life-long hobbyists to industry professionals, we enjoy learning about new things and meeting new people, and participating in spirited debates.

Quick Navigation

User Menu

Steve Williams
Site Founder | Site Owner | Administrator
Ron Resnick
Site Co-Owner | Administrator
Julian (The Fixer)
Website Build | Marketing Managersing