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Thread: Audible Jitter/amirm vs Ethan Winer

  1. #61
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    Quote Originally Posted by Phelonious Ponk View Post
    I would argue that riding the volume up during quiet passages, or any manner of playing the material at abnormally high volume for the purpose of pushing the distortions into audibility is cooking the tests.
    I agree, and I have learned to say "at normal levels" when discussing jitter and dither and the benefit of 24-bit recording. I'm pretty sure I never said "jitter is never audible in any circumstance," but if I did I meant any normal circumstance. If you have to crank the volume on soft parts such that playing other parts of the same music would blow out your speakers or your eardrums, then it's not a valid condition.

    As for blind versus double blind, I think that single blind can be adequate in many cases. I've tested people blind in my own studio to my satisfaction. I knew which file was which, but the listener didn't and I'm confident my facial expressions gave nothing away. The last the I did such a test I was facing away from the listener. I also test myself blind by closing my eyes so I can't see which state the solo buttons are in.

    --Ethan

  2. #62
    Quote Originally Posted by Steve Williams View Post
    That is too funny. I think you should "trademark" that term in audio at the very least
    Perhaps, but in a hobby filled with people who believe they are impervious to expectation bias, it's probably not worth much more than an occasional laugh, a consistent sneer. This place has its share of fire-breathing audiophiles, but it has some balance as well. Other boards bristle at the mention of any kind of objectivity. On another board I visit, there has been an on-going discussion of counterfeit hi-res - SACDs on Amazon, files on HDD Tracks - that have been discovered to be nothing more than upconverted 16/44.1, complete with the 20khz ceiling. The discussion has taken up 3 or 4 threads, many pages, and has covered the ethical considerations, the need for renumeration, a debate over the responsibilities of the producers vs. the retailers and on and on.

    What has hardly been touched are the implications of the fact that so many owners and users of these recordings had no idea they were not genuine until someone put a scope on them and published the information on the internet.

    P

  3. #63
    [WBF Founding Member] Ron Party's Avatar
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    Quote Originally Posted by Ron Party View Post
    Amir, <snip>

    I've read the description you've posted here and (in what seems like another lifetime) at AVS, and IIRC in all of the tests you've run you were listening through cans. Have you heard what you describe as jitter through loudspeakers?

    Quote Originally Posted by amirm View Post
    No I have not tested jitter using speakers. <snip>

    I was asked once whether I thought it would be as easy to hear these artifacts with speakers and I said no. Happy to elaborate once we cover some of the main points of the debate.
    Quote Originally Posted by Ethan Winer View Post
    I agree, and I have learned to say "at normal levels" when discussing jitter and dither and the benefit of 24-bit recording. I'm pretty sure I never said "jitter is never audible in any circumstance," but if I did I meant any normal circumstance. If you have to crank the volume on soft parts such that playing other parts of the same music would blow out your speakers or your eardrums, then it's not a valid condition.

    --Ethan
    A few additional thoughts, all of which tie into the concept of a person actually detecting what Amir has identified as jitter in real world situations.

    I would like to see this discussion to evolve in the direction of detecting jitter while listening through loudspeakers.

    Amir stated he has only detected what he has identified as jitter while listening through cans. He left a piece of bait out there about the unlikelihood of detecting the same while listening through loudspeakers. Given the wide misunderstanding of the subject matter and numerous (but IMO erroneous) declarations of the audibility of jitter, including some right here at WBF, Amir, I would like to ask you to further expound on this.

    I also think it is important to focus on Ethan's point about *normal* listening levels.

    I suppose there is a range of what might be considered normal, e.g., I know I like to listen at much louder levels than most I know. (I have a SOTA headphone preamp and what many have described as one of the top 3 cans ever made, but I cannot imagine turning up the volume anywhere near what I do when listening through loudspeakers.)

    Having stated my own preference, however, a discussion on the detection of what Amir describes as jitter at much lower listening levels through loudspeakers is essential to the discussion, particularly if we're looking for something that is -60 to -80 dB.

    A couple of other passing thoughts. It is my understanding that there is an abundance of gear for which jitter has been measured at less that 250 picoseconds. If this is the case, then when trying to detect the audibility of jitter by listening through loudspeakers, are we discussing a moot point, a question made quite significant since there are many DACs on the market in the 5 figure range?

    And, finally, how come there has been no discussion in this debate about jitter, or a jitter equivalent, in vinyl playback, which in a best possible case has only about 12 bits of dynamic range?

  4. #64
    Member Sponsor [Technical Expert] DonH50's Avatar
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    To address only the last question Ron raised: The jitter under discussion is related to the "timing noise" on the sampling clock in a digital system. There is no sampling noise in a purely analog system. There is broadband noise that could be compared to random jitter, and phase issues in tracking (and the electronics) that could be compared to deterministic jitter.

    In my opinion, dynamic range is a red herring in much of this discussion. Not because it does not matter, but because (a) there's usually more than enough dynamic range to hear the music above the noise, (b) like many other systems, our ears can pull signals from below the noise floor via filtering and averaging, and (c) pure noise is much less objectionable than distortion, whether induced by jitter, nonlinearity in the electronics, or something else.

    My 0.000001 cents - Don
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  5. #65
    [WBF Founding Member] Moderator RBFC's Avatar
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    I have what is perhaps an uninformed question:

    If jitter distortion is at -80dB (for example), is it possible that the combined distortions of the reproduction chain can become cumulative enough for total system distortion to reach typical audibility? Is it possible that jitter is one of the items to be summed as distortion approaches the threshold of audibility? Would it not make sense to reduce those distortions that can be effectively reduced to avoid an audible "sum"? Which distortions contribute most heavily to audible disruption?

    Maybe best for another thread or debate, but this "summation" seems like an important concept to me.

    Lee

  6. #66
    Member Sponsor [Technical Expert] DonH50's Avatar
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    "Summation" can be coherent or not, which changes significantly how much each component "adds" in the chain. Gain, bandlimiting and such also have an impact. Random jitter, like random noise, is not "distortion" from an engineering perspective, btw.

    Of course it makes sense to reduce all noise and distortion compenents as much as reasonable, where "reasonable" implies not only theoretically possible but practically realizable and at a given price point.

    I am not sure what you mean by "disruption". If objectionable to the listener, then distortion is likely more disruptive than noise in practical systems, and intermodulation or non-harmonic disortion more so than harmonic distortion. Most error sources do not sum linearly due to phase differences and are RSS'd -- root-summed-squared, e.g. RSS = sqrt(a^2 + b+2 + c^2 + ...) where a, b, c... are individual error sources.

    And yeah, this is getting a bit off just jitter... - Don
    Don Herman
    "After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
    Don's Technical Articles on WBF

  7. #67
    Quote Originally Posted by RBFC View Post
    I have what is perhaps an uninformed question:

    If jitter distortion is at -80dB (for example), is it possible that the combined distortions of the reproduction chain can become cumulative enough for total system distortion to reach typical audibility? Is it possible that jitter is one of the items to be summed as distortion approaches the threshold of audibility? Would it not make sense to reduce those distortions that can be effectively reduced to avoid an audible "sum"? Which distortions contribute most heavily to audible disruption?

    Maybe best for another thread or debate, but this "summation" seems like an important concept to me.

    Lee
    I suppose that it's possible, if a number of distortions were occurring at exactly the same time and at the same frequencies, that they could "sum," but this concept is more pertinent, I suspect, to the noise floor than it is to non-linear distortion. And in the context of this conversation, Amir has identified specific jitter artifacts he can hear at high volumes. If they are "summed," how could we possibly identify them as jitter?

    P

  8. #68
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    Quote Originally Posted by Phelonious Ponk View Post
    If they are "summed," how could we possibly identify them as jitter?

    P
    Assume you have a digital transport feeding a DAC. And assume that you make certain changes to that source and the sound changes. What would you conclude is changing?

  9. #69
    Quote Originally Posted by amirm View Post
    Assume you have a digital transport feeding a DAC. And assume that you make certain changes to that source and the sound changes. What would you conclude is changing?
    I would assume it was jitter. But you know what they say about "assume."

    P

  10. #70
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    Quote Originally Posted by Phelonious Ponk View Post
    I would assume it was jitter. But you know what they say about "assume."

    P
    I this case, they don't say anything bad .

    A digital source conveys two types of information:

    1. The PCM samples. If something goes wrong with these, you get glitches and audio drop outs. These failure modes are not of interest to us so we can assume all is well here if the music keeps playing.

    2. The timing of said samples. If the sound changes, and #1 is not impacted, then by induction, it is the timing of the samples which is impacted and hence jitter is the sole reason for audibility differences.

    If you read my posts though, you often see me mix in the term "other distortion" to talk about downstream conversion issues which indeed wind up being the sum of jitter and DAC non-linearities. There, we can't distinguish between the two without measurements (and even then it may be challenging at times).

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