[Albedo]

Depends.. if the source is jittery or not.

 

[Willakan]

And where is the evidence suggesting jitter in the order of picoseconds is audible?

 

[Albedo]

In the fourth harmonic..

 

[nick_charles]

 
Quote:

And where is the evidence suggesting jitter in the order of picoseconds is audible?

AFC Wimbledon (The real Wimbledon) are more likely to win the Champions League than for you to find any credible evidence of sub ns jitter audibility - best evidence to date suggests about 20ns for signal-correlated jitter (the worst kind) in a musical signal and 10ns for a single pure tone - claims to be able to to hear 2ps jitter and even different 2ps jitter spectra have never been backed up by empirical testing.
 
Jitter-worriers will say tests to date have not been good enough , that kit used was not up to scratch and so on, I review academic journal articles for a living and I've read every serious published study on jitter audibility - there is a good reason why there has been almost no research on jitter audibility by big audio companies since 1998 - it is not a problem except in the most technically incompetent kit , if you find a piece of kit with 10+ ns of jitter I can guarantee that it has other far more audible problems
 
 
 

 

[nick_charles]

Quote:

In the fourth harmonic..

Can you provide a citation including graphs and controlled listening tests - showing magnitude of distortion products for given levels of jitter ?
 
You should read Benjamin and Gannon , 1998
 
 

 

[Albedo]

Deterministic jitter or random jitter?

 

[Willakan]

It would be interesting if you could provide evidence for either signal-correlated jitter or other forms of jitter being audible in very small amounts.

 

[Prog Rock Man]

But once audibilty has been determined or not, it then has to be shown how jitter affects sound quality. Tom Nousaine found that he preferred the sound of a set up that had higher levels of jitter than another with less.
 
There are two missing links, audibilty and sound quality. Cable makers suggest both and fail to evidence either.

 

[Albedo]

Benjamin and Gannon said that a sensible difference is 10ns RMS with a 17KHz pure tone and with music 20ns RMS, but this paper are only concerning random jitter and IMO the level of deterministic jitter (inter-symbol interference dependent on transmitted data, periodic a.k.a. cycle jitter for example caused by switching PSU) and this distortion are more of a problem as the audible threshold are different. 
 
Which brings me to the 4th harmonic, it's not constant at all. 

 

[nick_charles]

 
Quote:

Benjamin and Gannon said that a sensible difference is 10ns RMS with a 17KHz pure tone and with music 20ns RMS, but this paper are only concerning random jitter and IMO the level of deterministic jitter (inter-symbol interference dependent on transmitted data, periodic a.k.a. cycle jitter for example caused by switching PSU) and this distortion are more of a problem as the audible threshold are different. 
 
Which brings me to the 4th harmonic, it's not constant at all. 

No, it is the Ashihara paper that has thresholds for Random jitter, which they found to be much larger. B and G used signal-correlated jitter which created distinct sidebands not the broadband spread you get from random jitter - look at the graphs Fig 1 and Fig 11 thru 14 and read the text before Fig 11 for the jitter generation routine - they also did sweeps to determine the differences in jitter effects at different jitter frequencies - random jitter is much less of a problem as it is basically just broadband noise and benign until it gets quite high, distortion sidebands are much easier to detect.
 

 

[Albedo]

Strange that sinusoidal jitter and residual harmonics are inaudible or is this in fact something that some prefer, as with DACs the odd harmonics will contain higher energy levels than the even harmonics, which I thought were audible because of duty cycles.

In the paper from 1994 by Dunn & Dennis "The diagnosis and solution of jitter-related problems in digital audio systems" I read the following "the harmonic nature of jitter-related artifacts means that they are potentially much more audibly objectionable than simple harmonic distotrion", which I thought the B & G paper was about.. as participants could just turn the jitter up and down, as such the cognitive factor is almost making it a sighted test. D & D compared six DACs and concluded that most DACs were good "as long as converter designers provide adequate jitter attenuation".

This is difficult.. as 2nd and 4th harmonics are of key interest to me for choosing a DAC, one can opt for a cheap one with skirt (warmer sound) and some of the harmonics that are distorted, and the other hand for 2.22 x the price one gets more attack (colder) and less harmonic distortion.

What those in the B & G test chooses as preferable is something I take under consideration, but in the end I think I'll opt for more attack and silver for a digital cable.

 

[nick_charles]

Quote:

Strange that sinusoidal jitter and residual harmonics are inaudible or is this in fact something that some prefer, as with DACs the odd harmonics will contain higher energy levels than the even harmonics, which I thought were audible because of duty cycles.

In the paper from 1994 by Dunn & Dennis "The diagnosis and solution of jitter-related problems in digital audio systems" I read the following "the harmonic nature of jitter-related artifacts means that they are potentially much more audibly objectionable than simple harmonic distotrion", which I thought the B & G paper was about.. as participants could just turn the jitter up and down, as such the cognitive factor is almost making it a sighted test. D & D compared six DACs and concluded that most DACs were good "as long as converter designers provide adequate jitter attenuation".

This is difficult.. as 2nd and 4th harmonics are of key interest to me for choosing a DAC, one can opt for a cheap one with skirt (warmer sound) and some of the harmonics that are distorted, and the other hand for 2.22 x the price one gets more attack (colder) and less harmonic distortion.

What those in the B & G test chooses as preferable is something I take under consideration, but in the end I think I'll opt for more attack and silver for a digital cable.

Julian Dunn did some interesting papers on jitter as did Malcolm Hawksford, but their papers are model-based,  neither of them did any empirical listening tests, also Dunn's model of audibility is predicated on very loud listening levels , so his 20ps threshold for jitter at 20Khz is based on listening levels of 120db above the threshold of hearing, for even an anechoic chamber this would be an absolute level of well in excess of  130db and in a listening room, well painfully loud if not actually dangerous.
 
You need to look at the magnitude of the distorton products to see why jitter is so hard to hear.  For example in Fig 17 on page 24
 
The distortion for the 300 ns rms jitter level is approximately 60 dB below the fundamental component of the piccolo note, 
 
and 300ns is over 1000x worse than a good budget CD player.
 
and then there is masking..... 
 
For example, a 4 kHz signal at 97 dB SPL causes the masked threshold at 2 kHz to be approximately 20 dB higher than the threshold of hearing in the absence of signal. The distortion due to 10 ns rms of jitter is -75 dBr for a 4 kHz sine wave. Since the threshold has been raised to approximately 20 dB SPL from the unmasked 0 dB SPL, the distortion at 22 dB SPL is 18 dB below the masked threshold of hearing. Jitter-induced distortion caused during the reproduction of sine wave signals becomes audible
only when the jitter is very large, or in the case of very high frequencies where the effect of masking in the range of 1 to 4 kHz is minimal and the distortion due to jitter is greater. Virtually all audio program sources have a spectrum that emphasizes the middle frequencies more than high frequencies (or Iow frequencies). Audio program signals that have strong high frequency components almost always have even higher levels of mid range or high mid-range frequencies. This acts to make the effect of jitter extremely difficult to hear with normal program material.
 

 

[Albedo]

The topic concerning audibility of jitter is as PRM point out maybe something of a preference, but to put it in another perspective the other DAC that I'm looking at has the same chip that was in a device costing $2000 a few years back. These days one can get the same chip implemented in a dirt cheap DAC, so.. as for cables as jitter it's always the factor of uncertainty as I have to take our precognitive absolute pitch perception into account.
 
I have a transport which I clock-locked with a DAC, there was a difference, but is it worth the price, same as cables, is it worth the price, when under other conditions one can't tell them apart. The perspective from Mid-Fi to High-End is debatable, as in.. a few years down the digital road your High-FI DAC is considered a POS amongst other Hi-Fi nuts.
 
Makes you wonder when you take a few steps back, reading ridiculous amounts of threads and papers get you to a conclusion, what matters the most is the music. Even through a POS gear with the right attitude it sounds good, but with Hi-Fi one tends to listen to ones equipment and the sickness of upgrades always tends to make one search for something that's not in nuances, but in attitude and such take a toll on ones wallet.
 
I think I'll rather take the blue pill..

 

[maverickronin]

Quote:

I think I'll rather take the blue pill..

Ok Cypher.  Just don't kill us while our backs are turned.  

 
On a serious note, I'd like to echo PRM's statement that knowing a bit about of the science can put your mind at ease.  OTOH it might dash a few hope of infinite improvement.

 

[bigshot]

Every instrument has a different 4th harmonic. Different volume, different frequency. It even changes characteristics with each note played. Nonsense is being spouted.