Senior HTF Member
- Jun 29, 2001
That level of jitter could be audible (as shown by Eric Benjamin and Ben Gannon's paper at last years San Francisco AES) but the conclusion that then jitter audibility in the ps region is possible is misleading by a factor of (possibly) a thousand.Chu, I spoke with the man a few months before his passing and he said:
"Myself and most researchers believe that the range of audibility is around 20 picoseconds of jitter."
This statement was made at the end of 2002, a full four years after that statement you referenced. So he clearly chnaged his mind.
Advances in jitter measurement have been substantial over the past four years and science has moved on to new conclusions about what is audible.
look, i can appreciate, from a technical point of view, companies such as Meridian, that strive to minimize distortions, improve upon things such as rotational stability, look to maintain signal integrity, in a sense apply a bit of overengineering. that's laudable in my estimation. jitter for some of their products is somewhere in the 200 ps area which i see as an honest attempt at quelling what's become the silliness with this jitter stuff.We record in hirez at 88.2 khz on an Alessis MasterLink at 200 picoseconds. Over time we experimented in lowering jitter by synching to an external Lucid Audio master clock which take the jitter down to 25 picoseconds.
The result? more clarity across the FR, more natural midrange, tighter and deeper soundstage. The clock was the only thing we changed and we have noticed this on transfering analog tapes, recording live events, studio work, etc. Clearly even low levels of jitter can make a difference. Michael Bishop and Bob Ludwig and others have also been exposed and understood the effects of master clocks and use them regularly in their acclaimed work.
This is not some audiophile dream, but something that is theoretically discussed by academics and applied in the real world by the top recording and mastering engineers.
Chu, I spoke with the man a few months before his passing and he said:"Myself and most researchers believe that the range of audibility is around 20 picoseconds of jitter.Did he present this to the AES in a same form as his previous papers?
Since he's not around we can only rely on your "testemony",which I must say is, far less convincing.
I take it you're familiar that modern DAC's have anti-jitter circuitry built in by the manufacturers.This works to a degree REDUCING the incoming jitter but the PLL used to reclock the incoming bitstream will still pass on some of the jitter - it must to adjust to bitrate variations in the incoming bitstream since the inbuilt buffer is so small.
I suggest anyone interested in this issue listen for themselves in as close to a DBT environment as they can arrange.
Some of the work Dunn was investigating were those 'other' things and one of them was cross-talk in the electrical components.The external DAC used was the same in the case I heard so I can't see how anything but jitter was the difference. I'll see if I can find measurements of the jitter for those players.
As an aside, the Chord DAC64 has a selectable buffer with no buffer, 1 sec and 4 sec options - the differences are quite audible with music and I can't explain the (smaller) differences between the 1 and 4 sec settings except that perhaps the larger buffer allows a much greater comparator period for the PLL so transport jitter is further reduced.
I'm an engineer, too, and understand what you are getting at but the problem is that the psychoacoustic model of our hearing is incomplete and some things can't be easily quantified yet. The study with test tones is a case of looking in the wrong area.
Vinyl? Not for me, pal. Whatever the shortcomings of digital recordings (which are damned few IMO), CD is the greatest mass market audio medium ever to succeed and I have severe doubts as to whether the hi-res formats will be successful or are even necessary (a major point of contention between Lee and myself).
I'm glad our government decided to support yours and Great Britain's - means I voted for the right mob.
Where are the moderators? This thread really belongs in the AV sources forum.
For all we know, the ultimate levels were different or the lower jitter clock resulted in less corrections being sent to the motor which may've resulted in improved stability...I just don't know and neither do you.Actually I do know...here's how:
1. Lucid calibrates to a jitter manufacturing standard of around 20PS.
2. We have heard this effect across several Lucid master clocks.
3. We do not change ANYTHING else in the recording chain so it has to be the effect of the clock.
4. Volumes were matched.
Here I have recounted real world experience Chu and you seem to want to blame the difference on everything but that of jitter. We have scientifically found the answer though - lower jitter from 200PS to 20PS. We have eliminated any other possible variation and we have reproduced the results over several recording sessions.
Craig, you are right about test tones. These often substitute for musical passage because the brain has an easier time finding them. But real music is a complex aggregation of same and such tones better produced at any frequency will add to the music's clarity and definition.