Originally Posted by amirm
Net, net, you are not going to get to the bottom of this using simplified tests.
Which begs the question why was so much space given to quoting a simplified test when the same document provided information about far more relevant tests?
The document quoted but not cited is:
"Eric Benjamin and Benjamin Gannon, "Theoretical and Audible Effects of Jitter on Digital Audio Quality", Preprint 4826 of the 105th AES Convention, San Francisco, September 1998"
That paper concludes:
The effect of clock jitter in the digital interface was studied extensively. Measurements of the jitter
spectrum of numerous digital audio sources, primarily DVD players, were conducted. A wide range of
performance was found. The jitter spectrum of a typical source can be characterized as a white noise
floor with one or many sinusoidal jitter components with a magnitude in the range of 10 ps to 10 ns
rms. The effect of jitter induced in the interface was studied and found not to be a significant factor for
short interconnection runs likely to found in a domestic environment. Several DACs and their DIRs
were measured in order to characterize the sensitivity to distortion induced by jitter. These results
were compared to each other and to results derived from simulations. Most DACs were found to be
similar to each other and to the simulation in terms of susceptibility to jitter-induced distortion. That
distortion is approximately -107+201og(F)+201og(J) dBr for sine wave signals at F kHz with J ns rms
of clock jitter.
Up-Down threshold and AB comparison listening tests were conducted to determine the threshold of
audibility for jitter-induced distortion. The threshold of audibility for pure tones was found to be about
10 ns rms at 20 kHz and higher at lower frequencies. For nearly all program material no audible
degradation was heard for any amount of jitter added below the level at which the DIR lost lock.
Certain program material was found in which an audible degradation due to jitter was heard. The
threshold of audibility for these programs was generally found to be in the range of 30 ns rms to 300 ns
rms for sinusoidal jitter. Finally, the audible degradation was found to correspond to measurable
changes in the spectrum of the program material.
So, pick your number:
- the absolute worst case, audible only under artifical lab conditions number which is 10 ns or 10,000 ps
-the reasonable worst case for musical recordings which is 30 ns or 30,000 ps.
I believe the worst-performing device that has been talked about around here lately was a now-obsolete AVR with HDMI inputs that had what, 5,000 ps jitter?
5,000 < 10,000 < 30,000 !!!!!!!!!!!!!!
By any criteria given
by the reference, that worst-performing AVR was free of audible jitter, even under the worst circumstances that could be contrived by one of the leading audio research labs in the world.
How many attempts to sell high-priced asynch USB DACs does that flush down the porcelain convenience? ;-)