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Jitter Correlation to Audibility - Page 6

post #76 of 331
Quote:
Originally Posted by Theta Alpha 1 View Post

Modern equipment has digital sheen in it.  You need to go backwards to older chips or use flagship stuff like AK4399 to achieve analog sound.  The effect is minimal but when you've listened to digital sheen for over 10 years it starts to get annoying.

If you want to go back in time to get analogue sound, pick up a used cassette deck at ebay. That will give you 100% analogue goodness.
post #77 of 331
Quote:
Originally Posted by stv014 View Post

With jitter:
Range_j.flac
Range_j2.flac
Both files have jitter added, but the second one has more. The sample might not make it the easiest to hear any jitter, so I increased the magnitude of the sidebands by 10 times, and the modulation frequency by a factor of 2. In the second file, all jitter is further amplified by a factor of 10.

Am I reading this right? Nick Charles provided specs for the absolute worst performing piece of consumer gear and you had to multiply the error by ten to make it at all audible?
post #78 of 331
Quote:
Originally Posted by bigshot View Post


Am I reading this right? Nick Charles provided specs for the absolute worst performing piece of consumer gear and you had to multiply the error by ten to make it at all audible?

 

I was not a great track to choose (The Damned) perhaps, single pure tones are always better, but nobody else was volunteering. I have about 800 classical CDs so if somebody has some better suggestions I will see if I have a copy to upload a segment from, Bach organ ? Sustained Piano ? Brass ? Since my high freq hearing is pretty knackered I cannot from ear come up with a good candidate. But I'll try the jitter test for a laugh !

 

Well with my laptop and Senn HD535 I could not tel j2 apart from the original but my hearing is not great !


Edited by nick_charles - 6/26/13 at 12:25pm
post #79 of 331

jitter gives the largest error products with the highest signal slew rates - bass would just waste amplitude while being too slow - but no one wants to listen to full scale 20 kHz sines - probably shouldn't expose yourself to them even if your hearing has already lost those highs

 

"music" has been found to have ~ 3KHz "power bandwidth" on average - the highs roll off proportionate to frequency above there - so music shouldn't be too sensitive to jitter even before considering masking

post #80 of 331
Thread Starter 
Quote:
Originally Posted by BlindInOneEar View Post

All this fussing over whether jitter might be causing a problem instead of just enjoying your music!   It's kind of like being so worried that there might be a monster under the bed that you end up forgetting all about that rather attractive person in bed with you. 
 

 

Nah..nothing stated here on the Sound Science board is going to affect my music enjoyment.  I’ve been enjoying my system just fine this past week. It was a funny comment though. :)

 

For me, it’s not a “worried” thing, but a cognitive dissonance thing.  I was flaberghasted when people here started telling me “jitter is inaudible”. I’m now even more flaberghasted that there isn’t much concrete scientific evidence (at least from what I can tell), that supports the audiblity of jitter case when it seems to be such popular industry-wide belief. My whole intention is to get to the bottom of the argument, and I'm trying to keep an open mind about things. I would personally like to see an end to all the bullsh***ng that goes on with audio related discussion boards, but that is most likely wishful thinking on my part.

 

For what it is worth, I believe Steve Nugent.  Everything he says makes plausible sense.  I truly believe he is a straight shooter, and not just some guy trying to hawk his products.  He seems to be an extremely passionate person, and I believe that the passion is what drives his intense obsession; not profitbility.  I really don’t understand certain people’s hostility towards him. Just b/c he has some expensive products to sell does not make him the boogie man.

 

Likewise, I do not understand the paranoia people have with the audio industry.  Where does this originate from?  It appears somebody(s) got ripped of at some point with a sub-par piece of expensive equipment, and now they refuse to listen to anything else while believing the entire "high end" industry is a sham. I believe if people actually take time to listen to various products like a USB/Spdif converters maybe they would realize what they believe is scientific fact is not at all correct. Everybody seems to have their minds already made up while refusing to believe any possible error on their part.

 

 

NOW.... back to the "science".


Edited by robertsong - 6/26/13 at 2:08pm
post #81 of 331
Thread Starter 
Quote:
Originally Posted by ab initio View Post


Jitter can only have an effect when signal is present. A jittery sequence of 0's still perfectly reconstructs the zero-amplitude signal. For that jitter to be present at -80dB full scale, the actual signal level has to be at 0 dB full scale. If the signal is below clipping levels, say -10 dB full scale, then those jitter side lobes are at -90 dB full scale.

 

If you guys want to hypothesize worst case scenarios when jitter could be most audible, I would be happy to do the sample calculation or create an artificial waveform with and without jitter of a specified size and spectral content.

 

Cheers!

 

Hi, is this (bolded part) for correlated jitter or non-correlated? Previous listening tests appear to be non-correlated jitter only, and I think this is major factor in the discussion. I'm under the impression that many who have posted here do not understand the difference, and why it is important to differentiate the two types.

post #82 of 331
Quote:
Originally Posted by robertsong View Post

I was flaberghasted when people here started telling me “jitter is inaudible”. I’m now even more flaberghasted that there isn’t much concrete scientific evidence (at least from what I can tell), that supports the audiblity of jitter case when it seems to be such popular industry-wide belief.

Welcome to Sound Science. Sorry about your preconceptions.
post #83 of 331
Quote:
Originally Posted by robertsong View Post

 

Previous listening tests appear to be non-correlated jitter only...

 

No, the Benjamin and Gannon study used correlated jitter and placed  audibility at about 10ns for a pure tone and about 20ns for a musical signal. 


Edited by nick_charles - 6/26/13 at 3:33pm
post #84 of 331

I believe that Steve Nugent is quite sincere and wholly believes everything he says I do not have an issue with him selling anti-jitter devices as nobody forces anybody to buy anything. Steve Nugent holds a large number of electrical engineering patents many to do with computer chips, I do not doubt doubt his engineering prowess at all. However, he has not made a good case for jitter audibility, he does a load of dog and pony shows but has never demonstrated the audibility of low amounts of jitter in any properly controlled tests

 

 

 

 

 

Quote:
Originally Posted by robertsong View Post

 

For what it is worth, I believe Steve Nugent.  Everything he says makes plausible sense.  I truly believe he is a straight shooter, and not just some guy trying to hawk his products.  He seems to be an extremely passionate person, and I believe that the passion is what drives his intense obsession; not profitbility.  I really don’t understand certain people’s hostility towards him. Just b/c he has some expensive products to sell does not make him the boogie man.

 


Edited by nick_charles - 6/26/13 at 4:34pm
post #85 of 331
Quote:
Originally Posted by leogodoy View Post

So what now? Accusing manufacturers of using "unscientfic tweaks and magic" on products design can get you banned.

Ok, again, what happened to xnor?
Edited by leogodoy - 6/27/13 at 6:21pm
post #86 of 331

read the rulz on moderation, discussion of moderation, banning - I don't agree that they are fair or wise but those are the terms - continuing to flout them, jumping into new threads with complaints will likely get more threads locked


Edited by jcx - 6/27/13 at 10:58pm
post #87 of 331
Quote:
Originally Posted by nick_charles View Post

I believe that Steve Nugent is quite sincere and wholly believes everything he says I do not have an issue with him selling anti-jitter devices as nobody forces anybody to buy anything. Steve Nugent holds a large number of electrical engineering patents many to do with computer chips, I do not doubt doubt his engineering prowess at all. However, he has not made a good case for jitter audibility, he does a load of dog and pony shows but has never demonstrated the audibility of low amounts of jitter in any properly controlled tests

 

 

 

 

 

I think pretty much everybody involved with audio is quite sincere and wholly believes everything they say.  I think the honest to goodness trolls and folks who peddle things they know to be bogus are few and far between.  That said, your point about properly controlled tests is the nub, isn't it?  So long as audio scorns such tests many audiophiles will continue to be unable to distinguish between the sincere but deluded and the sincere but correct.  Indeed, the more time I spend on audio boards the more I believe that most audiophiles simply do not want to make that distinction, nor even be reminded of it.   

post #88 of 331

Hi folks,

 

Audiophile by birth, head-fier by choice. I am new to Head-fi discussions, so I might have missed lots of discussions but this seems like a fun thread to post to.  I am a EE by profession.  Part of my daily routine is clock measurement for gigabit communication systems. That's frequencies in ranges of 10^9 Hz and higher.  So when I see picoseconds and ppm talked about in these threads, my mouth starts to water.

 

What I want to say is that when operating at frequencies that I am working on, where bit times themselves are on the order of few tens of picoseconds, every picosecond counts.  We take this further to breakdown the types of jitter in the clocks in order to understand the causes and possibly mitigate the the problem.  There are numerous ways to measure jitter. There is no industry agreement on how jitter is measured and which parameters are critical for a specific application. For the audio DAC applications I would imagine the more relevant jitter metrics are either cycle-to-cycle and/or period jitter.  The former are timing variations between adjacent clock cycles, where is period jitter is variation of any clock cycle with respect to desired (zero-jitter) clock period. These two metrics are actually interrelated through a difference equation. Furthermore, jitter is further broken down into random and bounded distributions. The random element is interesting because theoretically there is no limit to amount of jitter as more measurements are made over time. In other words, there is always some low but non-zero probability that there will be clock transition increasingly before or after the ideal clock time. Therefore, clocks jitter numbers need to be always measured with a qualifier, such as over how many clock cycles, or to a confidence level for a specific probability. My point I am trying to make here is that descriptions like "5ps peak-to-peak" have little value as a key element of information is missing.

 

I'd like to comment about the frequency deviation from nominal,  typically referred to as ppm of a clock source. This is usually defined as a static frequency offset with respect to the desired frequency of the clock source. As we all know, ppm stands for parts per million, with 1ppm being 10^-6 deviation.  As a simple example, I will choose an ideal 1000 hertz tone out of a DAC sourced by a +/-100ppm clock. A maximum of 100pm deviation will generate a tone somewhere between  999 and 1001 hertz.  In otherwords, the deviation simply manifests itself as a minute shift in pitch. I don't know how many people would be able to distinguish a pitch shift to that detail, but I am personally skeptical that even a fairly loose frequency deviation like this example will create perceivable difference. You can run a simple tone test yourself on your setup and see if you could determine the differences in pitch.

 

I am not going by get into the spectral characteristics of jitter here, which is a fairly complex topic. In itself it is often a cruical piece of information about the jitter. I suspect might be relevant to audio applications, but off the top of my head it's not immediately obvious what the impcat might be. I would imagine the resulting waveform is a function of jitter spectral characteristics, sampling rate, and sampling technology (PCM vs a sigma-delta of DSD).

post #89 of 331
Quote:
Originally Posted by Digitalchkn View Post
 

Hi folks,

 

Audiophile by birth, head-fier by choice. I am new to Head-fi discussions, so I might have missed lots of discussions but this seems like a fun thread to post to.  I am a EE by profession.  Part of my daily routine is clock measurement for gigabit communication systems. That's frequencies in ranges of 10^9 Hz and higher.  So when I see picoseconds and ppm talked about in these threads, my mouth starts to water.

 

What I want to say is that when operating at frequencies that I am working on, where bit times themselves are on the order of few tens of picoseconds, every picosecond counts.  We take this further to breakdown the types of jitter in the clocks in order to understand the causes and possibly mitigate the the problem.  There are numerous ways to measure jitter. There is no industry agreement on how jitter is measured and which parameters are critical for a specific application. For the audio DAC applications I would imagine the more relevant jitter metrics are either cycle-to-cycle and/or period jitter.  The former are timing variations between adjacent clock cycles, where is period jitter is variation of any clock cycle with respect to desired (zero-jitter) clock period. These two metrics are actually interrelated through a difference equation. Furthermore, jitter is further broken down into random and bounded distributions. The random element is interesting because theoretically there is no limit to amount of jitter as more measurements are made over time. In other words, there is always some low but non-zero probability that there will be clock transition increasingly before or after the ideal clock time. Therefore, clocks jitter numbers need to be always measured with a qualifier, such as over how many clock cycles, or to a confidence level for a specific probability. My point I am trying to make here is that descriptions like "5ps peak-to-peak" have little value as a key element of information is missing.

 

I'd like to comment about the frequency deviation from nominal,  typically referred to as ppm of a clock source. This is usually defined as a static frequency offset with respect to the desired frequency of the clock source. As we all know, ppm stands for parts per million, with 1ppm being 10^-6 deviation.  As a simple example, I will choose an ideal 1000 hertz tone out of a DAC sourced by a +/-100ppm clock. A maximum of 100pm deviation will generate a tone somewhere between  999 and 1001 hertz.  In otherwords, the deviation simply manifests itself as a minute shift in pitch. I don't know how many people would be able to distinguish a pitch shift to that detail, but I am personally skeptical that even a fairly loose frequency deviation like this example will create perceivable difference. You can run a simple tone test yourself on your setup and see if you could determine the differences in pitch.

 

I am not going by get into the spectral characteristics of jitter here, which is a fairly complex topic. In itself it is often a cruical piece of information about the jitter. I suspect might be relevant to audio applications, but off the top of my head it's not immediately obvious what the impcat might be. I would imagine the resulting waveform is a function of jitter spectral characteristics, sampling rate, and sampling technology (PCM vs a sigma-delta of DSD).

 

...my arithmetic is slightly off today. In my example, the frequency deviation is actually between 999.9 and 1000.1 hertz.

post #90 of 331
Quote:
Originally Posted by Digitalchkn View Post
 

Hi folks,

 

Hi to you too !

 

I am not going by get into the spectral characteristics of jitter here, which is a fairly complex topic. In itself it is often a cruical piece of information about the jitter. I suspect might be relevant to audio applications, but off the top of my head it's not immediately obvious what the impcat might be. I would imagine the resulting waveform is a function of jitter spectral characteristics, sampling rate, and sampling technology (PCM vs a sigma-delta of DSD).

 

 

 

 

 

here is an example of the effect of adding extreme amounts of sine wave jitter (From Benjamin and Gannon, 1998)

 

 

Quote:

The spectra show an easily visible tonal component at about 670 Hz that is proportional to the amount

of jitter added. This component is the lower sideband of the two that are created by the 1700 Hz jitter

applied during the listening test. There is presumably a corresponding upper sideband but it is not

visible in these tests due to the noise in the spectrum of the piccolo between the fundamental and the

second harmonic. Additional spectra measured with jitter of 30 ns rms and less showed no observable

difference relative to the unjittered spectrum. The distortion for the 300 ns rms jitter level is

approximately 60 dB below the fundamental component of the piccolo note, as predicted by the

simulation and by the measurements of the DAC


Edited by nick_charles - 9/6/13 at 3:00pm
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