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Soekris DAM1021 R2R DAC Measurements

Shadrach

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I may be out of date but I thought 'jitter' was defined as a delay in sending a packet from point A to point B. There can be a number of causes of jitter depending on the transmission method.
My logic may be faulty here, but how does one assign a perceived distortion to 'jitter' without measuring it when there are other factors that can produce distortion? It would seem given our ability to measure minute segments of time that 'jitter' using the above definition is measurable, but may not be audible.:confused:
 

amirm

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Jitter is not delay. Delay is just delay. :)

Jitter is variation in delivery of bits. In that sense, it modulates the music tones and with it, creates sideband distortions. This happens even if the bit delivery is perfect.

Jitter can be measured in time domain using specialized gear. Or much more easily and with far more precision by converting everything to frequency domain and looking at the amplitude of jitter sidebands. This is what I show in my reviews in the form of j-test.
 

DonH56

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It takes a lot of random jitter at the output to be audible and then it sounds like noise. Correlated jitter is more objectionable since it introduces fixed, typically nonharmonic, spurs.

For how random jitter relates to SNR and bit resolution, see e.g. https://www.audiosciencereview.com/forum/index.php?threads/digital-audio-jitter-fundamentals.1922/

Note I am talking about jitter in the sampled-analog domain, like the output of a DAC or ADC acquisition errors, and not jitter on a digital bit stream.

HTH - Don
 

Shadrach

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Jitter is not delay. Delay is just delay. :)

Jitter is variation in delivery of bits. In that sense, it modulates the music tones and with it, creates sideband distortions. This happens even if the bit delivery is perfect.

Jitter can be measured in time domain using specialized gear. Or much more easily and with far more precision by converting everything to frequency domain and looking at the amplitude of jitter sidebands. This is what I show in my reviews in the form of j-test.
Yes, I follow the J test theory. Thanks for the definition.:)
It used to be called delay where I worked many years ago. The delay wasn't a fixed period which is much the same as a variation in packet delivery I suppose. Digital signal processing was pretty new back then.:p
 

Shadrach

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It takes a lot of random jitter at the output to be audible and then it sounds like noise. Correlated jitter is more objectionable since it introduces fixed, typically nonharmonic, spurs.

For how random jitter relates to SNR and bit resolution, see e.g. https://www.audiosciencereview.com/forum/index.php?threads/digital-audio-jitter-fundamentals.1922/

Note I am talking about jitter in the sampled-analog domain, like the output of a DAC or ADC acquisition errors, and not jitter on a digital bit stream.

HTH - Don
So, given it was a long time ago I took an interest in the technicalities, is buffering still the preferred means of jitter reduction on a digital bit stream?
Correlated jitter; is this the jitter associated with sampling?
My knowledge is mainly based around networking.

Edit. I'll read the article. Probably easier.:)
 

Blumlein 88

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Good grief, what do those definitions even mean? Just randomly throwing words together? Should not have looked at that after eating lunch...

My guideline: "Don't sling mud with a pig; you just get dirty, and the pig likes it."
Maybe they also employ fractal wordsmithing tech.
 

Blumlein 88

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So, given it was a long time ago I took an interest in the technicalities, is buffering still the preferred means of jitter reduction on a digital bit stream?
Correlated jitter; is this the jitter associated with sampling?
My knowledge is mainly based around networking.
Correlated jitter is jitter correlated with the signal being passed. Not random. It will vary as the signal varies.
 

DonH56

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Jitter breaks down into two general components: random, meaning unrelated to the signal or anything else (e.g. Gaussian noise); and correlated, meaning related to something (may be signal, clock, power supply, etc.) It is the same for Ethernet, SAS, PCIe, etc. but the difference here is when a noisy clock is used to drive the DAC's clock directly. Sooo...

Reclocking the data stream, e.g. an asynchronous DAC, is pretty standard these days to eliminate (or at least greatly reduce) jitter on the incoming bits. Buffering is harder with some protocols (not my area of expertise) since, without the ability to check errors and ask for retries, you'd in theory need an infinite buffer to handle a continuous stream unless the sending and receiving end are perfectly tuned.

HTH - Don
 
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