3 ms·

The usual dogma among those with a passing familiarity with digital audio seems to be to the effect of, "Bits are bits - it doesn't matter where they come from.

The usual dogma among those with a passing familiarity with digital audio seems to be to the effect of, "Bits are bits - it doesn't matter where they come from." This, as it turns out, is not entirely correct. Jitter can be a substantial problem in digital transport and does have well-understood effects on overall sound quality, and certain DAC designs are much better at jitter rejection than others. Here, it's a bit of a stretch, but not entirely outside the realm of possibility for jitter to be affected at varying levels by the storage system in use, though there are a lot of variables here (router, UnitiServe, and Naim NDX) that may not have been adequately isolated. That being said, I don't deny that there's a substantial amount of 'snake oil' in the audiophile industry, and reviews like this should be considered with some skepticism - but that shouldn't mean we dismiss them outright. I would, of course, like to see tests indicating these differences, as - if they exist - they will be quantifiable with the right equipment, e.g., an Audio Precision analyzer.

pslam 12y ago
No, jitter is not a problem. It is more than a stretch to go from "jitter as a theoretical problem" to "jitter as an actual problem" - it is absurd. Don't even give this credence. The only way to make jitter audible is to do it deliberately, to the extent that the DAC would have difficulty even locking to it. At that point, it would likely end up dropping samples, and we're not really talking about digital audio any more. Audio marketing has been using crap like "digital jitter" as one of their snake oil sales tools for as long as digital audio has been commonplace. Don't give it even the slightest amount of publicity.
- Florin_Andrei 12y ago
  I used to design digital electronics in a past life. When the slave has locked onto the master clock, and remains there locked for a long time, it's game over. The slave becomes effectively a clamp-down filter on the master's real or imaginary deficiencies. Yes, the master does matter still, but a quality, stable slave acts as a damper. The slave's own jitter tendencies might be important - but then again, where do they end up? Mostly in the analog /dev/null sinkhole - the sampling frequency is far above the audio spectrum, the jitter components are too, mostly (unless it's low-freq drift), and the output of your DAC has a steep downpass filter. Jitter components are obliterated. That's assuming that jitter would matter at all even if it was not filtered out. But if a DAC is flickering that badly that you could hear it, it's probably a piece of trash anyway. Make sure the actual digital-to-analog conversion (the last link in the digital chain) is done well, and don't worry about anything else. Yes, you can screw up DAC design and execution, but nowadays most DACs are very good. This is not your grandpa's radio.
- TheOtherHobbes 12y ago
  You must be unfamiliar with the AES and other papers that describe audible jitter and the threshold at which it starts to become audible. See e.g. "Eric Benjamin and Benjamin Gannon, "Theoretical and Audible Effects of Jitter on Digital Audio Quality", Preprint 4826 of the 105th AES Convention, San Francisco, September 1998" or "The Effects of Sampling Clock Jitter on Nyquist Sampling Analog-to-Digital Converters, and on Oversampling Delta-Sigma ADCs, 87th Convention of the Audio Engineering Society, October, 1989" or Ashihara and Kiryu, etc (2005) https://www.jstage.jst.go.jp/article/ast/26/1/26_1_50/_pdf https://www.jstage.jst.go.jp/article/ast/26/1/26_1_50/_pdf
  - pslam 12y ago
    I am quite familiar and in fact that paper concludes that jitter is not detectable in normal consumer equipment: "About 25% of the listeners detected jitter when its size was 500ns. When it was 250ns, however, no listener could discriminate the sounds." ... "Nishimura and Koizumi made attempts to measure actual jitter of various DA systems during reproduction of music signals. They could not detect any jitter larger than 3ns in their measurements." ... "So far, actual jitter in consumer products seems to be too small to be detected at least for reproduction of music signals" ... CONCLUSION "The threshold values seem to be sufficiently larger than the jitter actually observed in various consumer products."
    - cnvogel 12y ago
      You should point out that typical jitter on the digital interface will be in the order of few 100 PICOSECONDS...
      - Joeboy 12y ago
        and is totally unrelated to any jitter on the storage system (unless it's so slow that it can't keep up with the DAC, which is unlikely to happen unless it's a 20th century hard drive or connected by a wireless/internet connection).
ctdonath 12y ago
Rule of thumb: when discussion of vanishingly small effects as they regard human perception (especially when applied to mere entertainment) devolve to requiring analysis "quantifiable with the right equipment", we've pretty much left the realm of human perception and the cost to obtain further improvements are pure waste.
- igrekel 12y ago
  Yep, I was just having this conversation with a friend recently, he was asking about high definition audio, high end usb cables, power conditioners other things like that. I own a good system to listen to audio from the computer (a Hegel H80) so he was asking me what I thought. I was having a hard tome to convince him that at one point you're better off spending money on better recordings and more music than going after the imperceptible (or not existing) differences through these kinds of equipment "upgrades".
- massaman_yams 12y ago
  My point wasn't about effects being so small they're imperceptible - it was that human perception is notoriously subjective (particularly in the audiophile world where people tend to want to hear differences even if they don't exist), and an AP analyzer (or similar) would provide a much more rigorous way of identifying if an effect was present. As far as perceptibility is concerned, ABX testing is a better method for that, and it really doesn't appear the individuals in this article conducted their listening tests via that method.
cnvogel 12y ago
But here's the thing: The clock source that goes into your DAC isn't influenced by the pattern of packets arriving from your storage system, it's typically a standalone oscillator sitting in the vincinity of the DAC and its controller in the shiny converter box... (for Pro-Audio it will be a rather dull 19" rackmount box, for audiophile stuff it will be brushed aluminum and have wooden knobs...). The only bad thing that can happen with the sound quality is that the computer isn't fast enough to keep up with supplying the controller next to the DAC (often in consumer hardware everything is integrated in one piece of silicon, though) with data, which is normally called a buffer-underrun. The ADC then doesn't know what to do and might produce clicks due to the sudden frames of silence inserted, some might just replay the last frame over and over again (stuttering or harsh noises). This is obviously audible to a huge extent. And yes, there are synchronization issues, and sometimes devices resample to bridge synchronization barrier., You'll be able to configure master/slave relationships, distribute word-clocks, ... but for the simple task of listening to a FLAC file of a Jazz Concert, those complications just don't apply.

pslam 12y ago

No, jitter is not a problem. It is more than a stretch to go from "jitter as a theoretical problem" to "jitter as an actual problem" - it is absurd. Don't even give this credence. The only way to make jitter audible is to do it deliberately, to the extent that the DAC would have difficulty even locking to it. At that point, it would likely end up dropping samples, and we're not really talking about digital audio any more. Audio marketing has been using crap like "digital jitter" as one of their snake oil sales tools for as long as digital audio has been commonplace. Don't give it even the slightest amount of publicity.

Florin_Andrei 12y ago
I used to design digital electronics in a past life. When the slave has locked onto the master clock, and remains there locked for a long time, it's game over. The slave becomes effectively a clamp-down filter on the master's real or imaginary deficiencies. Yes, the master does matter still, but a quality, stable slave acts as a damper. The slave's own jitter tendencies might be important - but then again, where do they end up? Mostly in the analog /dev/null sinkhole - the sampling frequency is far above the audio spectrum, the jitter components are too, mostly (unless it's low-freq drift), and the output of your DAC has a steep downpass filter. Jitter components are obliterated. That's assuming that jitter would matter at all even if it was not filtered out. But if a DAC is flickering that badly that you could hear it, it's probably a piece of trash anyway. Make sure the actual digital-to-analog conversion (the last link in the digital chain) is done well, and don't worry about anything else. Yes, you can screw up DAC design and execution, but nowadays most DACs are very good. This is not your grandpa's radio.
TheOtherHobbes 12y ago
You must be unfamiliar with the AES and other papers that describe audible jitter and the threshold at which it starts to become audible. See e.g. "Eric Benjamin and Benjamin Gannon, "Theoretical and Audible Effects of Jitter on Digital Audio Quality", Preprint 4826 of the 105th AES Convention, San Francisco, September 1998" or "The Effects of Sampling Clock Jitter on Nyquist Sampling Analog-to-Digital Converters, and on Oversampling Delta-Sigma ADCs, 87th Convention of the Audio Engineering Society, October, 1989" or Ashihara and Kiryu, etc (2005) https://www.jstage.jst.go.jp/article/ast/26/1/26_1_50/_pdf https://www.jstage.jst.go.jp/article/ast/26/1/26_1_50/_pdf
- pslam 12y ago
  I am quite familiar and in fact that paper concludes that jitter is not detectable in normal consumer equipment: "About 25% of the listeners detected jitter when its size was 500ns. When it was 250ns, however, no listener could discriminate the sounds." ... "Nishimura and Koizumi made attempts to measure actual jitter of various DA systems during reproduction of music signals. They could not detect any jitter larger than 3ns in their measurements." ... "So far, actual jitter in consumer products seems to be too small to be detected at least for reproduction of music signals" ... CONCLUSION "The threshold values seem to be sufficiently larger than the jitter actually observed in various consumer products."
  - cnvogel 12y ago
    You should point out that typical jitter on the digital interface will be in the order of few 100 PICOSECONDS...
    - Joeboy 12y ago
      and is totally unrelated to any jitter on the storage system (unless it's so slow that it can't keep up with the DAC, which is unlikely to happen unless it's a 20th century hard drive or connected by a wireless/internet connection).

ctdonath 12y ago

Rule of thumb: when discussion of vanishingly small effects as they regard human perception (especially when applied to mere entertainment) devolve to requiring analysis "quantifiable with the right equipment", we've pretty much left the realm of human perception and the cost to obtain further improvements are pure waste.

igrekel 12y ago
Yep, I was just having this conversation with a friend recently, he was asking about high definition audio, high end usb cables, power conditioners other things like that. I own a good system to listen to audio from the computer (a Hegel H80) so he was asking me what I thought. I was having a hard tome to convince him that at one point you're better off spending money on better recordings and more music than going after the imperceptible (or not existing) differences through these kinds of equipment "upgrades".
massaman_yams 12y ago
My point wasn't about effects being so small they're imperceptible - it was that human perception is notoriously subjective (particularly in the audiophile world where people tend to want to hear differences even if they don't exist), and an AP analyzer (or similar) would provide a much more rigorous way of identifying if an effect was present. As far as perceptibility is concerned, ABX testing is a better method for that, and it really doesn't appear the individuals in this article conducted their listening tests via that method.

cnvogel 12y ago

But here's the thing: The clock source that goes into your DAC isn't influenced by the pattern of packets arriving from your storage system, it's typically a standalone oscillator sitting in the vincinity of the DAC and its controller in the shiny converter box... (for Pro-Audio it will be a rather dull 19" rackmount box, for audiophile stuff it will be brushed aluminum and have wooden knobs...). The only bad thing that can happen with the sound quality is that the computer isn't fast enough to keep up with supplying the controller next to the DAC (often in consumer hardware everything is integrated in one piece of silicon, though) with data, which is normally called a buffer-underrun. The ADC then doesn't know what to do and might produce clicks due to the sudden frames of silence inserted, some might just replay the last frame over and over again (stuttering or harsh noises). This is obviously audible to a huge extent. And yes, there are synchronization issues, and sometimes devices resample to bridge synchronization barrier., You'll be able to configure master/slave relationships, distribute word-clocks, ... but for the simple task of listening to a FLAC file of a Jazz Concert, those complications just don't apply.