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Old 2nd January 2009, 08:54 AM   #1
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Default Jitter - gone for good?

I have been participating in a thread on another forum. In this thread, a poster states that jitter is no longer a problem. He also states it can be eradicated by resampling. Is this correct?

It's been several years since I did my theory on CD playback, and having worked in IT for the past 18 years or so, electronics has become more of a hobby than a profession.

Can anybody shed some light on the subject please?

Thanks,
Tony.
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Old 2nd January 2009, 12:04 PM   #2
jitter is offline jitter  Netherlands
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Default Re: Jitter - gone for good?

Quote:
Originally posted by audio_tony

Jitter - gone for good?
Nah, I'm still here .

Quote:
I have been participating in a thread on another forum. In this thread, a poster states that jitter is no longer a problem. He also states it can be eradicated by resampling. Is this correct?
I say he'd be wrong. Maybe some forms of jitter may be reduced by reclocking, but any manipulation may introduce new jitter. At least that's how I understand it.
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Old 2nd January 2009, 03:32 PM   #3
rossl is offline rossl  United States
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If the clock used for the resampling has jitter, then the new samples will have that jitter modulated into the audio stream.
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Old 3rd January 2009, 03:21 AM   #4
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The countervailing view is summed up pretty well on the jitter.de website...

http://www.jitter.de/english/how.html
Quote:
If you use an ASRC as a jitter attenuation device, the jitter at the input of the ASRC will be distributed into the output signal-data, and what was simple clock-jitter at the beginnig is now forever glued your digital audio signal, it has become something comparable to sampling jitter.

(I have to add here, that the designers of ASRC chips try to minimize the susceptibility to input clock jitter, and this is the reason why manufacturers use ASRCs in order to reduce jitter. It may sound a little better if you add an ASRC but the price you pay, is to loose the original sound quality that was contained in the input signal to the ASRC.)

The clock jitter at the output of the ASRC might be less, but the signal is not the same (the data has been altered), it now irrevocably "contains the input jitter" and the initial signal quality is degenerated.

Unfortunately sample rate converters are praised as jitter attenuation devices by some manufacturers, but they are not.
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Old 3rd January 2009, 10:16 PM   #5
jwb is offline jwb  United States
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That's a bunch of horse ****.

An ASRC does not modulate the input clock jitter into the output stream, except below the audible spectrum (< 10Hz). An ASRC only uses the input clock to estimate the IN/OUT clock ratio. This calculation is performed with an extremely low passband. You can't hear it.

It's possible that the input clock will somehow be modulated into the rest of your system, for example through the power supply rails. This, however, is a system design issue and not a feature of an ASRC.
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Old 3rd January 2009, 11:16 PM   #6
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Default Re: Jitter - gone for good?

Jitter is the current 'bÍte noire' of that section of the community which in restless discontent seeks to discover less and less plausible reasons not to enjoy what you hear.

Quote:
Originally posted by Oscar Wilde
...the unspeakable in pursuit of the inedible
Samples are just a string of numbers, fixed once recorded. You have no control over the jitter in recording.

How much jitter is present at playback time depends on the exact technology employed to deliver the string of numbers to the DAC, and where the timing information comes from. It is almost certainly entirely possible to produce a cheap playback system with current technology where the jitter is below the threshold of audibility.

The arguments are all about whether particular systems meet this criterion. As technology advances such considerations will eventually be squeezed to extinction.

Please, Lord... make it soon.

w
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Old 3rd January 2009, 11:32 PM   #7
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Originally posted by wakibaki
As technology advances such considerations will eventually be squeezed to extinction.
That assumes the jitter fetishists are amenable to reason.
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Old 4th January 2009, 12:13 AM   #8
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Default Re: Re: Jitter - gone for good?

Quote:
Originally posted by wakibaki
Jitter is the current 'bÍte noire' of that section of the community which in restless discontent seeks to discover less and less plausible reasons not to enjoy what you hear.




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Old 4th January 2009, 12:22 AM   #9
jwb is offline jwb  United States
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I don't know about fetishes, but it is certainly possible to achieve phase noise sufficient low to claim 24 effective bits during playback, and I don't know anybody who believes that the 24th bit is audible. Therefore, in my opinion, jitter is a solved problem.
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Old 4th January 2009, 12:37 AM   #10
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jwb, that's an elegant argument.

w
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