Interesting tidbits about "jitter" in digital audio reproduction

Phelonious Ponk

New Member
Jun 30, 2010
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The problem is you eliminated 2 distinct components, the DAC and the USB receiver.
Hard to tell "Who dunnit".

I'm inclined to suspect the USB receiver (adaptive mode probably) and/or the direct electrical connection between the PC and the DAC over the power and/or data lines of the USB.
Nice bit of guesswork anyway.

It would be interesting to try a modern USB implementation (asynchronous) preferably combined with galvanic isolation using the same source.

Would it be jitter either way?

P
 

Vincent Kars

WBF Technical Expert: Computer Audio
Jul 1, 2010
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What you describe is in line with how jitter can manifest itself
Of course we can not exclude any other cause.
If you want to know for sure, you need to measure the unit.
 

Phelonious Ponk

New Member
Jun 30, 2010
8,677
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What you describe is in line with how jitter can manifest itself
Of course we can not exclude any other cause.
If you want to know for sure, you need to measure the unit.

The unit is long gone. I didn't keep it. It sounded good, but didn't clearly differentiate itself in my system. Vincent are you and "Roseval" one in the same?

P
 

Nicholas Bedworth

WBF Founding Member
May 7, 2010
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Maui, where else?
Generally it's hopeless to attempt to measure jitter without, say, $100K of highly specialized test gear that has been very carefully set up, with external noise injection circuits, stablized clocks, and so forth. And then the question arises, what kind of jitter, what is the bandwidth, and on and on. Jitter is a multifarious (and nefarious) beast. A single jitter "number" without a lot of explanation and details may not be reliable or indicative. Often characterization of the jitter has to be done through indirect methods, which makes things even more difficult.
 

Nicholas Bedworth

WBF Founding Member
May 7, 2010
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Maui, where else?
Excellent paper on PLL

Basically, eliminating most of the jitter from the incoming clock data can be effected using phased-locked-loops (PLL). This technology has come a long ways in the past 4-5 years.

Read this paper, and the others posted previously. You'll be pretty much at the cutting edge of understanding all this. There's a lot marketing hysteria and misinformation out there. These are the real answers.

Digital is very, very difficult to do correctly.
 

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MylesBAstor

Well-Known Member
Apr 20, 2010
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Basically, eliminating most of the jitter from the incoming clock data can be effected using phased-locked-loops (PLL). This technology has come a long ways in the past 4-5 years.

Read this paper, and the others posted previously. You'll be pretty much at the cutting edge of understanding all this. There's a lot marketing hysteria and misinformation out there. These are the real answers.

Digital is very, very difficult to do correctly.

Nick:

As I remember PLL loops are nothing new. My older Altis digital gear going back 10 years used PLL. What has changed in the intervening years?
 

Nicholas Bedworth

WBF Founding Member
May 7, 2010
312
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0
Maui, where else?
Check out the Frandsen Travis paper on their JET PLL... there are PLLs, and there are PLLs ;) Basically the JET engine combines real-time digital, meaning numerical, processing with analogue technology to optimize performance. This allows for all kinds of exotic shaping of the PLL's filtering capability. The PLL becomes more of a processing pipeline, which can be arranged in several different configurations, and on and on. Quite interesting. My review of Daniel Weiss' INT 202 FireWire to AES3 interface in 6moons (appearing in a few days) will go into some of the details.

This part demonstrates, IMO, the dividing line in high-end consumer audio. There are those who can incorporate software-based solutions into their designs, and those who don't.
 

microstrip

VIP/Donor
May 30, 2010
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This is a great discussion, and I learned a lot from some of the contributions. However I feel that one aspect is not being considered - the real recordings we listen have jitter, as the process of digital conversion from analog is not free from timing errors.

Did any one take a systematic study of the jitter in digital professional recording machines? How does intrinsic jitter of the recordings influence our perception of the effects of jitter in the reproduction chain?
 

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