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Low-Jitter USB: Dan Lavry, Michael Goodman, Adaptive, Asynchronous

Discussion in 'Computer Audio' started by jude, May 20, 2010.
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  1. bigshot

    At what point can human beings not hear jitter any more? That's the real question. One can split hairs and then split the splits, but at some point it all becomes academic as you say. If 121ps is academic, then what about double that? Then double again? Is it still academic? When does it stop being academic. Where is the line that defines what is "good enough" for 100% of human ears. This is the question that the high end audio industry has a vested interest in NOT answering.

    The truth is, the last big improvement in listening to reproduced SOUND (as opposed to technology or convenience or storage or editing or recording or mixing) occurred half a century ago with FFRR and stereo. Since then, the improvements have been more and more academic.

    For listening to home stereos (as opposed to recording and mixing) we long since crossed the line into academic improvements. The people who argue about the number of angels on the heads of pins aren't really interested in listening to music. They just want to whip it out and compare lengths on paper. That's why we see claims of golden ears accompanied by vehement denials of the validity of any sort of testing that generates anything other than more papers covered with numbers.

    Jitter is a hoodoo. Even in a $50 Korean no name CD player it's well below the threshold of audibility of even the most golden ears. There are things that are hard to achieve in home audio, but a fancy DAC or high end CD player won't get you any closer to it.
  2. nick_charles Contributor


    Sorry, I missed this part before. Er, no the word you are looking for is Psychotic, suggesting losing touch with reality. My first two degrees are in Psychology and my dad was a Psychiatrist so I have an interest in mental health issues, words are important, Schizophrenia is a sort of bucket term for several flavours of Psychoses. Anyway, your suggestion that 100,000s of people cannot be wrong is absurd. Of course they can be imagining things, why, because people are massively suggestible and prone to self-deception and post-rationalization and other cognitive biases. These kinds of things have been observed so often it is laughable to suggest that just because X people believe something they must be right. This goes for purveyors as much as consumers. Leaving aside religion (proper) there are many wonderful and strange different belief systems with millions of sincere proponents they must by your reasoning be right, Scientology must be right and so on.
    If there really is a fundamental problem with ps jitter as an audible issue where is the good non-anecdotal evidence for it? Where are the controlled listening tests to show that ps jitter of any kind is audible?
    I have trawled the AES library year after year; nobody has ever shown ps jitter to be an issue ever.
    Now , there is lot of debate about the way to measure jitter such that even jitter device manufacturers and audio hacks cannot agree on it. So we have an ambiguous rather amorphous concept badly understood that is immeasurable in a rigorous fashion and yet it must be a problem. Am I the only one seeing delusion here?
  3. bigshot

    40,000 Frenchmen can't be wrong!

    I may be the only one old enough for that joke.
  4. regal
    Nick as an engineer with a good scientific background I appreciate your post,  but I think people look at science to elucidate  Decarte's body as a machine.   Why is their no good scientific evidence (studies)?  Because who is going to fund it?   Look up ASTM,  that is the first step,  right now there is no standard to measure jitter, no calibration,  basically just numbers with little meaning.  So its hard to publish a decent paper without an ASTM.   And what has been published is rubish,  you do know that many scientific papers are not worth the paper their written on, no?   The human perception of hearing is a very complex "mechanism" that science has little understanding.  One of the reasons it interests me is that it is uncharted territory,  the studies done on jitter audibility are simplistic, not based on real sound waves found in nature or music.
    I do think the "theory" of mass delusion is if not pompous, borderline delusional,  but coming from a psychologist you get a pass :)
    You really need to sit down with a good set of headphones, a great DAC and amp and listen to a half dozen transports.  If they all sound the same to you I would be surprised.
  5. nick_charles Contributor


  6. regal


    OK so the transport industry, engineers, marketers, and customers are on the same level of psychosis as the Salem witch hunters,  this has to be because you read a couple obscure no-name papers published years ago.   Yet you refuse to sit down and compare a couple transports,  don't trust your ears enough.   I know you are more down to earth than you are coming across,  where is your pragmatism?
  7. bigshot
    It's actually probably not all that much of an exaggeration to call hifi nuts crazy.

    I trust my ears. I have never been able to hear the difference between cd players. I can hear huge differences between speakers and rooms though.
  8. regal


    with speakers its hard to tell differences in sources,  I thought we were talking headphones.
  9. bigshot
    Speakers sound more like real musical performances. If you want the most truthful sound reproduction, you don't use headphones. They're OK for recording when you don't want sound spilling back into the mike, but serious listening and mixing is always done on speakers. Cans are a compromise for people who aren't allowed to play their music out loud by neighbors or unsympathetic family members.
  10. regal


     And for people who don't want to spend a fortune on speakers,  dam I could have sworn I came here to talk to headphone users,  must be at the wrong web address. [​IMG]  Cans reveal details like no speakers I've heard are able.   Listen I used to be Mr dutiful Engineer not believing picoseconds of anything could affect my playback, thinking jitter was propped up by stereophile to lure people into spending a fortune on transports,  but over the years I ended up with several transports and they all sound different,  not only that I realized the studies were based on meaningless numbers.  All my transports are verified bit-perfect. There is more going on to make a blanket statement that all transports sound the same.  You guys remind me of the newtonian physcists who would never accept the duality of electrons.   Fact is there has been piss-poor research into the subject of jitter and its a personal decision to trust ones ears or some old papers.
  11. Dynobot


    Nah, we are talking the magical world of Eq's and Jitter.  Where in the minds of some [Eq's] are the end all be all to perfect sound, and the other [Jitter] is clearly audible and kills the listening experience.
    In the mist of it all we have people stroking their egos at each others expense with exaggerated claims of pseudoscience.
    Topics like this have been discussed over and over on every audio forum on the Internet, they always start the same and end up the same.  In the end there are test cases, white papers, spec sheets, Degrees, Industry affiliations, etc. flying all over the place.  All in the attempt to protect ones ego and be [the one] who is right.  Meanwhile in the real world there are people enjoying music using every method imaginable.
    Budley007 likes this.
  12. Syan25
    Bottom line - there is never anything perfect. Whilst it is a joy to try to achieve perfect sound reproduction, and we always should try to get the best we can possibly have, we have to keep in mind that that perfection will never exist - no matter how far we go with technology. Keeping things balanced.
    It's funny how on forums like these - we often ridicule those who buy Dr. Beats or lesser equipment that are based on fads and not on SQ. However, for these people - they are making themselves happy - and they enjoy the music from what they buy. To them they are getting that auditory satisfaction that they want.
    Same here with hi-tech low jitter technology or controlled acoustic environments,  also...we are, including me, satisfying our need for auditory satisfaction. And that is how it should be.
    That is what is firing this long discussion. It's more a debate of the differences in what people get satisfaction from regarding technology and sound.
    Anyway - that is my take on this....we are all of us on the same playing field here. Each to their joyous own! 
  13. nick_charles Contributor


    I merely showed one example of masss delusion of the kind you will not attribute to the hifi transport industry, would you prefer it if I used the word suggestible  which is perhaps less derogatory. Let us examine the effect of expectations on human perception for a while, in the 1980s Masters and Clark amp test listeners were convinced they heard obvious huge differences between amps, when knowledge of what they were istening to was removed they could not, Harman showed that listener ratings on speakers were massively biased by visual appearance and knowledge of cost, when these were removed ratings altered drastically even to the point of changing the order of reference. PIO2001 recounts a listener who rated a cheap Onkyo as crap compared to his Bryston, but he was listening to the Bryston all the time. Cable swappers who omit to swap cables evoke the same reports of change. It is called being human.
    Of course I do not trust my ears when there is poor control on the tests. The only sighted tests that are of any use are level matched rapid switching ones using aligned samples, I have done these a lot but even these allow expectations to interfere and delays are damaging.
    I'll give you an example. I was testing the different inputs on my DAC (USB and SPDIF), I got two time-aligned samples on different devices and was able to switch in an A B C order (Coax, Optical, USB)  so I could do the Optical(B) to USB(C)  switch smoothly. I heard no difference, I tried this many times. But at the end of each cycle I had to go through the null Coax setting to get back to the optical , I always felt that the optical was louder than the USB I had left two positions, it was an illuion caused by the delay where there was no sound.
  14. bigshot
    I don't think it's a good idea to constantly be striving for more and more perfect sound unless the improvements are called for by your own ears. All over this forum I see people asking things like "Should I upgrade my DAC?" and they get a million answers, but no one ever asks "What in the sound are you trying to improve?" If you don't clearly define what you're trying to fix, you end up chasing theory well past the point of audibility. It isn't hard to do listening tests. I've done a bunch myself. Numbers are great when they reflect what you can hear. But they're a big fat lie if you lose sight of scale.

    Most problems with sound are due to bad recordings, mechanical acoustic problems, imbalances in settings or distortion. The plain vanilla rebook CD player is perfectly capable of producing excellent sound. If yours doesn't, odds are it has nothing to do with zeros and ones and everything to do with the rest of the system.
  15. USAudio

    Very true.  They're also good for removing poor room acoustics from the equation.
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