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Audibility of Jitter, Proposing a series of tests
Arnold B. Kruege...
post Sep 26 2013, 03:31
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QUOTE (krabapple @ Sep 24 2013, 12:52) *
FWIW, here's a good faith attempt to supply examples of audible jitter


http://www.cranesong.com/jitter_1.html



It appears to be at least partially in error. File B is inverted. You probably want to invert it to avoid an irrelevant potentially confounding variable.

I picked two files at random and subtracted them producing a residual that averages about 70 dB down. The residual, when raised by 40 dB may show signs of FM distortion being the difference between the two files as it sounds kinda warbly.

This post has been edited by Arnold B. Krueger: Sep 26 2013, 03:34
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Arnold B. Kruege...
post Sep 26 2013, 03:48
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QUOTE (Gigapod @ Dec 27 2006, 11:27) *
QUOTE (cabbagerat @ Dec 27 2006, 14:33) *
The threshold of audibility of phase noise in ADC and DAC clocks
...

I would suggest you begin with a working definition of "Jitter", which you could post to the HA Knowledgebase. Is jitter "phase noise" ?


Depends what you call noise. If your definition of noise includes only random or pseudo-random signals then no. Jitter error is FM or phase modulation. The modulating signal or modulating function can be and often is deterministic.

QUOTE
What does it sound like?


Depends on the nature of the modulating function.

If the modulating function is random or pseudo-random then all that happens is that the noise floor gets raised. The nature of the rise may have a broad spectrum or it may have a narrow spectrum that is bunched up around the signal, in which case you have modulation noise.

If the modulating function is deterministic and reasonably simple (it often is - e.g. a sine wave or a square wave) then in small quantities it adds a rough character. If the modulating function has high enough amplitude but still has a simple spectral content, then it sounds like a vibrato.

If the modulating function is complex then the effects are more like what you get with a random or pseudo random function.

QUOTE
What does it do to a sine wave that goes through ADCs and DACs ?


Simply stated it FM or phase modulates the signal.

QUOTE
Does it matter at all ?


Jitter matters if it is large enough to be audible.

One curious factoid is that traditional forms of analog recording and playback are often relatively speaking engorged with audible jitter, and the golden ears never seem to hear it. Digital transcriptions of analog recordings perpetuate their jitter unless the jitter has been forcibly removed, which can be done.

Jitter in digital gear tends to be much lower and is generally inaudible.

QUOTE
What is the order of magnitude of jitter in PCs? and in high-end audio equipment?


It can be all over the map. PCs with high quality audio interfaces and even just good cheap ones are generally free of audible jitter.

But as usual it is impossible to make a perfectly general statement.

This post has been edited by Arnold B. Krueger: Sep 26 2013, 03:49
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stv014
post Sep 26 2013, 10:56
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Not sure if this is relevant here, but there is currently an ongoing discussion - including listening and hardware tests on the last few pages - related to jitter and its audibility on another forum here.
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Arnold B. Kruege...
post Sep 26 2013, 12:35
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QUOTE (stv014 @ Sep 26 2013, 05:56) *
Not sure if this is relevant here, but there is currently an ongoing discussion - including listening and hardware tests on the last few pages - related to jitter and its audibility on another forum here.



Quote from that article:

"For instance, Empirical Audio uses two oscillators that are both specified at 2psec RMS jitter. The two oscillators sound radically different to me when used in a re-clocker in a resolving audio system."

Sighted evaluations - IOW golden eared techno junk.

Next! ;-)
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krabapple
post Sep 27 2013, 02:59
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QUOTE (Arnold B. Krueger @ Sep 25 2013, 22:31) *
QUOTE (krabapple @ Sep 24 2013, 12:52) *
FWIW, here's a good faith attempt to supply examples of audible jitter


http://www.cranesong.com/jitter_1.html



It appears to be at least partially in error. File B is inverted. You probably want to invert it to avoid an irrelevant potentially confounding variable.



Did you read the explanation of the files?

"All files are phase canceled with the B file, which is the reference."

http://www.cranesong.com/jitter_2results.html

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stv014
post Sep 27 2013, 10:53
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QUOTE (Arnold B. Krueger @ Sep 26 2013, 13:35) *
Sighted evaluations - IOW golden eared techno junk.


That may be the case for the opening post, but not necessarily for many of the replies. For the listening tests, skip to page 8. UltimateMusicSnob again has some surprising ABX results, although for now only with rather high amounts of jitter (however, the actual levels of the jitter products are fairly low).

QUOTE (krabapple)
Did you read the explanation of the files?

"All files are phase canceled with the B file, which is the reference."


There might be a real problem, however, the difference files have far higher level (I mean by orders of magnitude) than expected for the amount of jitter, even if the gain applied to the files is taken into account.

This post has been edited by stv014: Sep 27 2013, 10:56
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2Bdecided
post Sep 27 2013, 13:04
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I think UltimateMusicSnob is becoming the new Guruboolez, but probably to a far higher degree.
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Wombat
post Sep 27 2013, 14:38
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QUOTE (2Bdecided @ Sep 27 2013, 14:04) *
I think UltimateMusicSnob is becoming the new Guruboolez, but probably to a far higher degree.

This, or a very sophisticated troll payed by High-End business to reinforce audiophile 'facts' in popular forums laugh.gif
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2Bdecided
post Sep 27 2013, 17:35
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Don't joke, a similar thought had crossed my mind - though the jitter being ABXed is still a lot greater than anything normal equipment would exhibit.

I haven't followed it, but there's a report that he's ABXed pre-ringing at 22kHz or something?

FWIW I've tried and failed to ABX the files over there. It's strange - when listening critically I can hear plenty of flaws in the source content, but not the "large" amounts of jitter. I'd have to listen far less critically to enjoy such flawed sources (or for that matter any music), so it's interesting what other people hear and care about.

Even the artefacts that I can ABX (mp3 encoders etc) are often far smaller and less annoying than the faults in a typical good recording. To me, at any rate.

Cheers,
David.

This post has been edited by 2Bdecided: Sep 27 2013, 17:37
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Wombat
post Sep 27 2013, 19:46
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i already made up my mind when he described things he listens for around the Ravel sample. Since i lately often appeared as bugger in here i decided to shut up about it.
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greynol
post Sep 27 2013, 19:56
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It's difficult to describe the tonality of noise, but this really isn't the place for a discussion of the Ravel sample.

This post has been edited by greynol: Sep 27 2013, 19:57


--------------------
I should publish a list of forum idiots.
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Arnold B. Kruege...
post Sep 28 2013, 14:32
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QUOTE (krabapple @ Sep 26 2013, 21:59) *
QUOTE (Arnold B. Krueger @ Sep 25 2013, 22:31) *
QUOTE (krabapple @ Sep 24 2013, 12:52) *
FWIW, here's a good faith attempt to supply examples of audible jitter


http://www.cranesong.com/jitter_1.html



It appears to be at least partially in error. File B is inverted. You probably want to invert it to avoid an irrelevant potentially confounding variable.



Did you read the explanation of the files?


I read this which justifies my comment:

http://www.cranesong.com/jitter_1.html

"At exactly the same playback level, listen to each sample all the way through - several times. Become familiar with the recording. The files are the same level"

What is unclear about "listen to each sample"?

QUOTE
"All files are phase canceled with the B file, which is the reference."


Since polarity can be audible, this conditions the proposed test for 100% positives in any comparison between the unknowns and the known, for a reason that has nothing to do with jitter.

We are talking about the validity of following the instructions to the listener, and nobody not even us should encumber the listening test with details about how the samples were made.

The proposed test is still flawed by the introduction of an irrelevant but potentially confounding variable.

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