[time-nuts] from Sputnik to CD

Henk ten Pierick henk at deriesp.demon.nl
Tue Oct 9 14:29:36 EDT 2007

1. At first: thank you Greg Burnett.

2. There are some nice similarities between audio and time keeping.
  As an example: the relation between jitter and what is audible is a  
difficult one. There are not yet good models developed. The models  
are based on single or dual tone stimuli.
Also: the relation between temperature behaviour and oscillator  
frequency is a difficult one. There are not yet good models  
developed. See the excellent articles of Rick Karlquist on this.
The way out for this temperature modeling problem is the oven or even  
the double oven. For audio and jitter such a solution is not possible.

3. It is clear to me, and has been clear to me always, that I can not  
hear pico seconds jitter on a clock. But it is also clear to me, and  
has been demonstrated by others, that effects can be heard that  
correlate very well with the measurements of this pico second jitter  
value. It is very well audible in music on loudspeakers.

4. I do not have a model for what can be heard in relation to jitter.  
Psycho-acoustic models are most based on single or dual tone stimuli.

5. W.r.t. the SPDIF interface, it is the low frequency content of the  
jitter is caused by the loop. It is the proportional part of the loop  
that make another difference. Driving the drive from the dac, thus  
reversing the direction, helps and shows a big improvement.

6. Noise like jitter is more audible than sine modulation. I do not  
know why.


On Oct 9, 2007, at 19:33, Greg Burnett wrote:

> It would have been nice if our group (with our impressive, collective
> talent, logical, scientific and mathematic abilities) could have
> brainstormed this topic with a positive outcome. Might we have hit  
> on an
> idea or principle that would further our (and the worlds?)  
> understanding of
> this topic?
> The question about the relationship between SPDIF (and AES/EBU)  
> clock jitter
> and audio DAC fidelity is of interest to those of us (who can hear  
> these
> differences).  For example, might there be a second order effect  
> (with a
> high sensitivity coefficient) regarding the effect of timing jitter  
> on the
> overall process of ADC / DAC audio processing (as some, here, have
> suggested)? ...Or other mathematical relationships yet to be  
> defined or
> understood?
> But, unfortunately, when it comes to this topic, there are always a  
> few
> discussion killers. Who wants to risk their peer status by offering  
> their
> findings, or theories (after some have posted put-down links,  
> generally
> implying that those who can hear these differences are fools)?
> --Greg
> ----- Original Message -----
> From: "Dr. David Kirkby" <david.kirkby at onetel.net>
> To: "Discussion of precise time and frequency measurement"
> <time-nuts at febo.com>
> Sent: Tuesday, October 09, 2007 9:54 AM
> Subject: Re: [time-nuts] from Sputnik to CD
> Poul-Henning Kamp wrote:
>> I have paid my dues in the HiFi world, but I have always insisted  
>> that
>> there be a solid scientific basis for any product I bought.
>> When faced with claims that picosecond jitter can be perceived by
>> the human ear, my flim-flam-o-meter blows a fuse.
> You might like to take a read at this.
> http://www.g8wrb.org/useful-stuff/audiophools.pdf
> which is in a web site of mine. To find it quickly, I used Google,  
> then
> see a few places link to it  - I've no idea what this page says - I
> guess it might be Romanian with the .ro domain.
> http://www.hi-fi.ro/fhifi/viewtopic.php? 
> p=186493&sid=e8b54fc8fa8a51f312d6a3770381ef99
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