how can digital be different

Here's another paper for you to regarding the currrent discussion, they may contain some useful info, and then again they may be full of DBT ?, however they are fairly strightforward

Jitter conceptive theroy

 

No disagreement there, but again Altman states (albeit without the figures to back it up that would have been nice) from his experiments:

Again, rather than just attempting to pick holes in other peoples information and score points...if you have any counter-evidence POST IT!

Thanks for the summaries.

Again agreed, and one of the points I made above. But if those people who do know what they're talking about don't explain or correct misapprehensions, you can't blame journos (or simple amateurs) for getting it wrong. I suspect the "hobbyhorse" is that jitter seems the one effect that could lead to differences in digital performance (note that this discussion has nothing to do with anything downstream of the DAC chip itself)

So that "groan" was entirely due to YOUR misreading/misinterpretation of what I wrote, of which every word of that comment I stand by (and which your comments in no way contradict). As a simplified example, a peak error of 100ns could be seen from a) a single 100ns component at 10kHz or b) a single 100ns component at 100Hz or c) 10 10ns components at 100,200,300,400,500,600,700,800,900 Hz, or d) some much lower equally distributed wideband noise....or.... These will produce very different distortions in the output - those of the third example being a bunch of distortion products each about 20dB (can't remember the modulation formula exactly ATM but it's something like that) down on the former two, and (if anything is audible at all ) would sound quite different.

Now we get to the nub of the matter. So Benjamin and Gannon (and since you cited it I assume you agree) would seem to imply that digital cannot sound different. Is this actually your position? (My view, maybe simplistic, is that it is possible, and unfortunately seems remarkably prevalent, to design DACs sufficiently badly for it to sound different, but that it's not necessary).

The whole point of this thread has been to try and describe what is and is not important in digital audio transmission, and how. Up to now it seems that it's primarily myself, PeteH and michaelab that have been actually interested in volunteering any information. Someone else's turn now (step forward dat19).

Ah...WM - thanks for that link....I remember reading some of it a while ago (but don't remember much of what I read ). Interesting that it does seem to contradict/query the Benjamin and Gannon result in the "Audibility Considerations" sidebox right near the end.

 

While in fact citing the same Benjamin and Gannon pre-print There's something a bit odd here - Benjamin and Gannon finding that "for nearly all program material no audible degradation was heard for any amount of jitter added below the level at which the DIR (Digital Interface Receiver) lost lock" (thanks dat19) doesn't really square with the claim in that link that "Benjamin and Gannon found... with music, none of the subjects found jitter below 20ns rms to be audible". Are they saying that the DIR lost lock at 20ns?

 

Dunn is backpeddling on his earlier theoretical result in the light of B&G's paper..

Pop Quiz:

What products do Audio Precision make?

What are they used for?

Who buys them?

Suppose you were writing a technical document about jitter and your company sold test instrumentation for measuring jitter. Which of the two quotes would you use: #1 or #2 ?

 

Oh well, Pete....seems that's not to be. As we also seem to be the only three with any interest left here, I guess this thread should now be declared dead. Still, the thread originator (ChrisD - who seems to have given up long ago) should have some idea now about the issues...but unfortunately not a tremendous amount about how serious they are (or need to be) in practice.

And now I'm outta here for some seriously satisfying sliding sur les snowy slopes. :banana:

 

Boy is this one still going?

A very time ago I saw an article in a mag.. by a guy that is now well known and, at the time, was just about the only person that was interested in getting to the bottom of the phenomenom of transports sounding different. Basically what he found was that the sound of a transport wasn't absolute.. it was dependant on the DAC that was used in combination with it. The reason? He found measureable differences between the the levels and type (ie spectrum) of Jitter being generated by the transports. This had an effect at the input stage of the DAC and the resulting spurious output at the analogue stage of the DAC was dependant on the Transport/DAC combination.

That's basically it in a nutshell. The cable has an effect because of it's potential to alter the level and type of jitter even further.

I thought it was well accepted these days that jitter can be audiable..in the sense that it can add colouration (ie distortion) to the analogue output stages of the DAC.

GTM

 

Which magazine?

Playboy
What HifI
Journal of the AES
IEEE Spectrum

But you can't remember his name?

Hugh Hefner
Alvin Gold
Robert Adams (Analog Devices)
Stan Lipshitz (Waterloo University)

And he had appropriate test instruments? Because you're looking at tens of thousands of dollars of equipment to measure pico-seconds of jitter...

Did he also conduct a study to correlate the jitter (on a test instrument) with the ability of people to detect through their ears the effects of jitter. Putting that another way a proper test which married engineering and subjective testing?

Again, just because it can be measured with a test instrument, does not mean it can be heard...

It is widely accepted in the Hifi press that jitter is audible, but none of the journalists have participated in properly conducted tests. Look at the way they review gear: the box arrives, the open it, they know who made it and how much it cost and the opinion is formed before it is plugged in. They never participate in blind tests to save themselves the humilation of not being able to demonstrate their "golden ears". Yet, audiophiles lap up the bullshit written by these reviewers and products succeed or fail based on a handful of badly conducted reviews.

So, if the article you mention was written by Hugh Hefner, appeared in Playboy and the test instrument was a bunny bouncing her boobs on the transport, then that is probably a far more interesting article, and more technically accomplished than anything by Alvin Hughes or Jimmy Gold writing in WhatHiFI+Stereophool.

If on the other hand this article was by Lipshitz or Adams and appeared in the IEEE or JAES, then it would have merit. No such article has been forthcoming, and the articles that have been published have concluded that jitter is not audible.

Let me take another tack: You only have to look at the group of people who become audiophiles: middle aged men, on the verge of age related hearing loss, with large disposable incomes. They want to buy a set of expensive gadgets, and need some justification for the expense, so as not to look stupid for buying something sonically indistinguishable from a much cheaper product. When it comes to CD transports "jitter" is the perfect excuse: jitter is an obscure topic in EE, and if someone should ask you why you've "wasted so much money on a CD player" you can mumble "oh it's jitter I read about it in hifi porn monthly, and it's definately audible, a reviewer swore blind he heard it in a single sighted test, it's the minute differences in clock blah blah" and 99.9% of the time the person asking will assume you know what your about. Then every once in a while someone will say, "OK then, I'll bring over my $100 dvd player and I'll blindfold you and swap between your transport and my DVD player, you tell me which is which"

So, here's my advice:

If your on a budget, spend your money on speakers - they are where the action is.

If you want an expensive transport, just buy it. When someone asks why you spent so much say that "you liked the way it looked"; "it's got a great warranty", "women love it", "I enjoy owning it", just don't go around claim huge sonic improvements because sometime, somewhere, someone will double blind test you

 

Of course! I understand it now. We are all deaf. Why didnt I think of that before?

I could have saved myself thousands by just going out and buying a £100 mini system. What a fool I've been.

 

I'd subscribe immediately.

-- Ian

 

Well thats 2 copies of ''tits and gear'' monthly puplication ordered!

Brazilian virgins astride a B&W snail-shell nautilus, Siberian vixens in a snow-scape with a gyrodec... .....steady!!!...

 

Countering an argument with ridicule:SLEEP:

The guy was Keith Miller in HiFi Choice, a few years ago when it was slightly more technical than it is now. He was somebody who believed all measurements could say why things sounded different.

 

Lee, who's ridiculing who

So I guess he's looking for another job then. As I recall, he tried to actually measure audible differences. The fact that he couldn't on occasion suggests either that the differences were imaginary, or that he didn't know what to look for. No one of these explanations is any more plausible than the other.

 

dat19, I'm with you.

 

You forgot the part about the "hospitality" provided by manufacturers for journalists reviewing their products Unfortunately I don't seem to be able to get hold of the journals you've mentioned which is a little annoying as I'd like to have a look at some of those articles now.

I hadn't twigged that it was the same Dunn writing that Audio Precision document - it makes a lot more sense now So just to clarify, when Dunn says that Benjamin and Gannon found 20ns jitter to be the perception threshold, that's in fact a misrepresentation of Benjamin and Gannon's results? ie. basically Dunn is making out that jitter is an audible problem, whereas Benjamin and Gannon found that it wasn't?

Stereophile is an odd mixture of intelligent writing of high integrity and absolute out-and-out credulous nonsense - the editorial style seems largely to be the latter but there are some genuinely clever people contributing sometimes.

And don't forget to green pen the Playmate's breasts for best results