An interesting paper on jitter audibility - Page 4

I dont agree that you con conclude either point (1) or point (2) above.

IMO, all it shows is that the tweaked-out audiophile systems are more resolving than the one in the first experiment, which is no surprise, given that I have yet to hear a stereo salon build a good-sounding system, in any city I have visited...

It also shows that the college students may have untrained ears, or minds for this type of listening. It takes experience to hear these things and not to go down the garden path...

It certainly does not prove that 100psec jitter cannot be heard by humans. It only demonstrates that using these particular systems with this group of listeners that the threshold of audible jitter was relatively high.

Steve N.

First, I have Audio Engineering schooling, but I am a EE with 30 years digital design and management experience. This is my moniker, nothing more.

Secondly, I am not proposing that measurements are not important. I have a lot of measurement tools that I use myself daily. However, I do not ascribe to the notion that just because it cannot be measured using classical techniques or is perceived to be at some low "threshold" of audibility, that it is not audible. They are still discovering things that humans can hear that they previously though were inaudible. The brain is a powerful tool, and this is what makes our hearing so good, not just stirrups and eardrums....

And furthermore, I like to thing "outside the box", believing that there are audible things that typical measurement techniques are not showing. Being in the cable business for 10 years has taught me that much. I'm not saying that the phenomena cannot be measured, only that typical techniques are not showing them or that the perceived "thresholds" of these measurements are artificially high.

Steve N.
Empirical Audio

Your 3rd point is an excellent one, as are the others. I have found myself, that in order to highlight and make audible certain phenomena such as jitter, it is critical to choose the optimum program material, ala music tracks. I can play any number of tracks to an audience that will not expose the effects of jitter, even really large amplitude jitter. But the object is to expose the jitter, so careful selection of tracks that do this is warranted. Playing tones is equally useless in this regard IMO. I have found that it needs to be music with HF transients and good imaging depth and width, and not too busy.

Steve N.
Empirical Audio

So, here's a question for you, Steve. When you do the single-blind listening test, what is the setup? In this paper, at least, they adjusted the jitter by using software, so that everything else in the signal chain is constant (between listeners obviously). When you ask someone to listen to two systems, A and B, with differing levels of jitter, what are the variables that change besides jitter? Without using software, which would probably be difficult to program less than 100 ps of jitter, how do you know you are testing the audibility of jitter, versus some other change in the signal chain. For example, it would clearly be nonsense to switch between two different DAC's, let's say Benchmark and Bel Canto, and claim differences between the two are due to differences in jitter alone. I'm sure these two have different jitter measurements, but there is so much more involved than that. Can you give us an example, just one real world example, of how you tested the audibility of jitter using a controlled experiment?

I wholeheartedly agree with this.
I would like to add:
The formulas, "laws" , methods and measurements the engineer uses are a "working model" of the reality he tries to deal with. It gives a view on what he thinks is reality and some means to predict what will happen in reality in certain circumstances and under certain conditions.
It is a tool. A map of part of reality as we know it.
It is not reality. It is just a model of it.
The map is not the territory.
In the territory are numerous things that are not on the map.
In reality are numerous things that are not in the working models of science.

The jitter demonstrations that I have done compared the following in chronological steps:

1) Stock CD Transport playing a commercial CD track into modded P-3A DAC using S/PDIF
2) Stock CD Transport playing low-jitter copy of same track into modded P-3A DAC using S/PDIF
3) Modded CD Transport (same model) playing low-jitter copy of same track into modded P-3A DAC using S/PDIF
4) Computer playing same ripped track using Off-Ramp USB converter and S/PDIF to modded P-3A DAC
5) Computer playing same ripped track using Off-Ramp USB converter and I2S to modded P-3A DAC

DAC was the same one used for all experiments, same preamp, same amps, same speakers. The jitter was reduced (more precise and clear imaging) in each step. The listeners are all in front of the equipment, so they cannot see what I am doing. The playback equipment is changed back and forth using A/B teminology, changing which ones is A and B at random etc.. Much like what you get when you are being fitted for glasses.

The vast majority of listeners were able to hear an improvement in each of the 5 steps. A few had limited HF hearing, so they didn't. The only difference was the jitter in the digital signal(s). Measurements were not taken, but I had previously looked for the difference in jitter between the S/PDIF and the I2S from the Off-Ramps and I cannot see it on my 2nsec resolution scope. If it was a 500psec difference, I would have seen it.

You must understand that my CES setups are some of the most resolving that you will find at CES. It is essentially my same reference system that I use for the business. I have complete control over all components, speakers and cables. I dont share with any other vendors. Everything in the system is built by me or modded by me.

Steve N.

Well, I think we're getting closer to something meaningful. So, let me ask. What do you mean by "low-jitter copy"? I assume you have ripped a CD track, and then burned it again using some "low-jitter" technique. How is this done?

More importantly, without your actually measuring the change in jitter, let alone whether it is increased or decreased, why should one take it at face value that the copy is lower jitter? If you could show us some data (jitter spectrum, for example) for your copied CD's versus the original, then your test would have much more weight.

Also, when your "testers" at CES are doing the listening, do they know which source they are listening to? If so, one can easily make the arguments for a) placebo or worse b) they are just being polite.

And BTW, what does it mean when you say I "Jeff Goldblum you"?

Is that something you can tell me in public?
Isn't that a children's movie? Seems I did hear of it.

Originally Posted by Toe :
TO: drarthurwells. Just a heads up, in that long reply to ezkcdude you seem to have completely forgotten to provide any actual evidence, or even a coherent hypothesis, of how chaos theory applies to jitter being something that's audible, or to cite a source that does.

Good to see someone else understands Chaos theory.

One other factor is amplification of error effects in a source. A very small error (in reading a CD) goes through many steps of processing and amplification before it even reaches a speaker or headphone. A small reading error can then emerge as much larger an error before reaching a speaker or headphone. Related to large scale chaos eventually emerging from an insignificant small beginning.

Doesn't make any sense if: the analog recording is free of timing/phase errors, and the analog to digital conversion is free of timing/phase errors, and the embedding of data on a CD is free of any timing/phase errors, and if Santa Claus brings me the 72 virgins I asked for.

Yes. I use a battery-powered Superclock clocked CD writer. It is definitely lower jitter than the original, as is the Reality check. Reality Check did shoot-outs with me at CES last year. They were both excellent superior copies

Steve N.

The CD copies were verified to be bit-identical to the original, so the only variable changing is the jitter.

The Testers did not know until after they voted what they were listening to.

Steve N.