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I keep reading about Jitter..what does it sound like? Is it audible??
Good post, Ethan. It's obvious that the author of the Positive Feedback article is bias, using the words "I believe" frequently when speaking of the audibility of jitter. No one cares what he "believes;" we care about the facts. I think its pathetic that he dismissed the controlled ABX tests, stating the systems probably weren't resolving enough, or that the source wasn't. Give me a break! Excuses, excuses, but the results remain the same.I'd imagine if jitter did get to the point of audibility, the offending product should immediately be taken off the assembly line/recalled, as it should be deemed defective. Of course, some people might like the change in sound they get from it. Tubes add distortion that people like (including me), so why not add jitter?
The weak link in this chain IMO is easily the human ear. As Ethan states, you talking about an effect that is 20-30dB or more below the noise floor of a CD, which is quite low. Quite a few people struggle to listen to -30 to -40 dB on their receiver, let alone hearing that much difference below a noise floor. While an interesting phenomenon, I just don't have the budget to go after so small an effect, the next 10K I spend is going towards the room and perhaps a tube amp for my SongTowers.
Ed -Why not just build a tube pre-amp?Gene
So I'm not worrying about Jitter, if its not audible..screw it!!
I keep reading about Jitter..what does it sound like? Is it audible??I have noticed that between playing back CD's via my PS3 and playing back wav files via SB that sometimes the wav files sound faster as far as tempo goes-is that jitter??? Thanks Ed L.
is the noise pulse rhythm close to the beat of the pop tune (the Men at Work sample)?
Jitter is a timing variation that manifests as FM sidebands and/or noise. These artifacts are typically 20 to 30 dB softer than the residual noise floor of a CD, so it's not likely to be audible. But it's very difficult to create jitter in controlled amounts for conclusive testing. Here are some links that I think give a good real-world evaluation:Artifact Audibility Report Does Your Studio Need A Digital Master Clock?The first link above is a set of audio files you can listen to that play nasty sounding artifacts at various levels below the music, to determine for yourself how soft noise must be to not be audible.The second is a scholarly attempt to mimic jitter artifacts using software, in order to hold controlled listening tests.The third is a "teaser" for a for-pay article ($1.49) at the Sound On Sound magazine site. This article will be free to read in another five months, but I can reveal the answer now because the author has already discussed it at length in other forums. After testing several converters with several brands of external clocks, using an external clock never improved the jitter and in all but one case made the jitter worse.--Ethan
Nevertheless, these results tie in with work by others that indicates that 16-bit data jitter of any kind needs to be less than 200ps or so if it is not to produce measurable effects in the analog signal (footnote 5), which in turn means that even though the data are reclocked, the crystal clock in the CD player or the PLL in the processor that do that reclocking need to hold their word-to-word timing accuracy to better than 10 parts in a million. And that time precision needs to be preserved during the digital data's travails on its way to the DAC, something that in my opinion is, frankly, unlikely.The audible effect of jitter suggested by these simulations would be to add a signal-related grundge and lack of resolution as the analog signal's noise floor rises and falls with both the signal and the jitter, while any periodicity in the jitter—at the power-line frequency and its harmonics, for example—will throw up frequency-modulation sidebands around every spectral component of the music. The "clean" nature of the original analog signal will be degraded, "fuzzed up" if you like, to produce the typical, flat-perspectived, often unmusically grainy CD sound.
all jitter measurements need to be taken with a grain of salt, as there isn't a standard for measuring jitter. It's therefore very hard to compare any numbers that aren't made by the same method. At least if you are comparing numbers arrived at by the same method, you know that the relative levels of jitter in the measurements are accurate.
I have a master clock/slave system working on my home system that was specifically designed for it, and it has been measured to reduce jitter from about 300ns to about 200ns. The difference in SQ with and without the Master clock isn't subtle.
I'm not impressed by any of the 3 links in the above quote.
Jitter isn't just "sidebands" or "noise" - it's heard as a form of distortion and as noted in one of the articles, can effect imaging.
I've personally been tested in double blind tests and can identify jitter in the 15-30ns range, and I know of a few others who can identify it at the level of 10ns. This is way below the threshold of "hundreds" of ns cited in one of the articles.
I'm not sure the SoundonSound article has a lot of relevance to home audio, it's about a studio setup. I have a master clock/slave system working on my home system that was specifically designed for it, and it has been measured to reduce jitter from about 300ns to about 200ns. The difference in SQ with and without the Master clock isn't subtle.
