DAC improvements slowing down?

BBC studies are worthless IMO. They need better system and trained listeners as well as good quality tracks. I doubt if they had any of these three.

I have made improvements in the jitter of my products on the order of 30psec P-P and easily heard the difference.

Steve N.
Empirical Audio

Mapman,

Thank you for the clarification. Your explanation matches my understanding. Based on studies done at the beginning of the development of digital sound reproduction jitter was studied and the threshold of jitter was determined. There are no modern DACs that have jitter beyond what people can hear, but yet there is lots of talk about it. So what makes one DAC sound different than another if it is not jitter?

http://downloads.bbc.co.uk/rd/pubs/reports/1974-11.pdf

How are your studies better than the BBC?

Like I said, they need a better system and trained listeners as well as good quality tracks. I doubt if they had any of these three. The results point to that.

Also, the nature of the jitter is important. If they are generating random jitter, then this is not at all like the jitter in real audio systems. It is usually correlated in some way.

Jitter has three attributes:
1) amplitude
2) frequency
3) distribution

All of these are important and not just one measurement. They all vary with each other.

Steve N.
Empirical Audio

I believe you are familiar with Dr. Kiryu's study jitter detection in humans. His findings were that even trained people could detect less jitter than what the BBC reported.

https://www.jstage.jst.go.jp/article/ast/26/1/26_1_50/_pdf

Where are the scientific studies published by any non-marketing organization showing jitter is detectable even in the sub 200ps range?

It doesn't because it can't be done. It is great to develop an ultra-low jitter device for a feat in engineering, but for sound benefits??? I suspect the dust on speaker drivers has a bigger distortion impact than modern day jitter.