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An interesting paper on jitter audibility - Page 5

post #61 of 112
12/20/06 at 11:23pm
Quote:
Originally Posted by hciman77 View Post
1) Jitter on CDs - does that make sense ? i.e the bits are read correctly or not and buffered into the word clock and then clocked out. Any timing variations on read would surely be irrelevant unless bits were wrong or somehow the buffer was not filled, can that happen ?. I thought jitter was only a problem at D/A and A/D stages ?
There are no bit errors with my CD's. Very clean, treated and no scratches. The Transport PLL reacts to the changing bit-rate from the disk read and jitter is the result. If you dont believe me, I can ship you a rewrite so you can hear the difference yourself.

Quote:
Originally Posted by hciman77 View Post
2) I think the 3;4 step may be flawed. Computer transports are much better at error correction than CD transports as they cannot tolerate a single bit error, thus going from 3:4 must improve bit error rate i.e a variable enters here.
There is no error correction. The data is read error-free during the rip and the playback from the Computer is just a transfer from memory to the USB port.

Quote:
Originally Posted by hciman77 View Post
3) A modded transport may have other changes such as different SNR, THD, FR, Dynamic range, RFI noise and so on, can you verify that all these were unchanged in the mods
The Transport is improved by the mods, so the power noise levels, the edge-rates, the impedance matching etc.. are all improved over the stock transport. These things all improve the jitter in the S/PDIF output, nothing else.

Quote:
Originally Posted by hciman77 View Post
4) Did you check the bit error rates on the S/PDIF and I2S cables ?
Not saying the changes didnt improve things but not sure you have proven that you have isolated jitter as the culprit[/QUOTE]

Again, I seriously doubt if there are any errors on the CD read. The I2S does not error-correct. If there is any drop-out or error on the I2S, you will hear a pop. The only thing changing here in every case is the jitter, not the data.

Quote:
Originally Posted by hciman77 View Post
5) Did you verify that some listeners actually had worse HF sensitivity and that only those listeners failed or was this your interpretation for those who failed ?
I asked if the one listener that did not hear the difference in one case had some kind of hearing loss. He didn't believe so, but further tests that I did with other music tracks verified that he did.

Quote:
Originally Posted by hciman77 View Post
5a) What was the highest frequency on the track ?
I used two tracks. They had cymbols and bells etc.... Probably in the 16kHz range. I dont know for sure.

Quote:
Originally Posted by hciman77 View Post
6) Did any listeners with HF deficiencies get it right ?
None said that they had deficiencies. The one that did denied it.

Quote:
Originally Posted by hciman77 View Post
7) Define vast majority and few
We had probably three sets of 8-10 listeners, about 25. The few was one.

Quote:
Originally Posted by hciman77 View Post
8) Did you check that the audio levels were the same for each condition ?
The DAC was identical and the digital feed data identical as well as the preamp settings. They were the same gain.

Quote:
Originally Posted by hciman77 View Post
9) What exactly did you say to listeners, this is important as it is very very easy to accidentally skew results by varying instructions ever so slightly or accidentally exposing your expectations i.e "NOW listen to this"
Wife is calling me - will answer this later....

Steve N.
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post #62 of 112
12/21/06 at 12:24am
Thread Starter 
Quote:
Originally Posted by audioengr View Post
There are no bit errors with my CD's. Very clean, treated and no scratches. The Transport PLL reacts to the changing bit-rate from the disk read and jitter is the result. If you dont believe me, I can ship you a rewrite so you can hear the difference yourself.
Cheers, and I will happily pay postage and materials costs. If you could send me a normal copy and a jitter-reduced copy but just mark them A and B, thanks. Bung me your paypal address and I will send you some cash.
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post #63 of 112
12/21/06 at 1:08am
Quote:
Originally Posted by hciman77 View Post
Er, the man does hold something like 15 patents, 5 are audio related, for cables and connectors, so however strange his approach may seem to you (and me as it happens) I dont think it is fair to decry his engineering credentials.

A nice sig I saw at rec.audio.opinion is

Music is art
Engineering is science

Actually this is wrong anyway as engineering is strictly speaking the application of methods and techniques and knowledge which have been derived or discovered elsewhere (often by science)

Theodore Von Karman, an aerospace engineer, says, "Scientists discover the world that exists; engineers create the world that never was."
Actually that's exactly why I reacted perhaps strongly to Steve's statement. I have over 25 years of experience in designing electronics and a few patents to my name as well, so I think I know what engineering is all about, and I must say I still find it odd that a trained professional would discredit his peers simply because they believe in one of the main principles of science and engineering - validation by others.

So let me rephrase what I'm trying to say: Whether it's a scientific discovery or an engineering application, the procedure or the result must be able to be replicated by others, and that's where measurements come in. Why? Because unfortunately in acoustics, as well as many other applications, people just don't hear the same, and measurements are used as marks to render a more objective view; so others can validate and/or improve upon it.

Now as I have stated in my previous post, whether the measurements are meaningful depends on whether it is the correct technique and instruments used to obtain these measurements; nonetheless, that's no excuse to downplay the significance of measurements and those who believe in it in general.
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post #64 of 112
12/21/06 at 2:37am
Quote:
Originally Posted by odmanca View Post
Now as I have stated in my previous post, whether the measurements are meaningful depends on whether it is the correct technique and instruments used to obtain these measurements; nonetheless, that's no excuse to downplay the significance of measurements and those who believe in it in general.
Measurements are great. But the biggest determiner as to whether a measurement is meaningful to a home stereo enthusiast is if it is in the range of human perception. Frequencies that only bats can hear and time shifting too small to be perceived aren't worth sweating over.

See ya
Steve
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post #65 of 112
12/21/06 at 10:20am
Originally Posted by audioengr:
There are no bit errors with my CD's. Very clean, treated and no scratches. The Transport PLL reacts to the changing bit-rate from the disk read and jitter is the result. If you dont believe me, I can ship you a rewrite so you can hear the difference yourself.

Quote:
Originally Posted by hciman77 View Post
Cheers, and I will happily pay postage and materials costs. If you could send me a normal copy and a jitter-reduced copy but just mark them A and B, thanks. Bung me your paypal address and I will send you some cash.
Your system's source jitter, and other colorations in your sysem, could mask the differences making discrimination difficult between the jitter-free and jitter-containing materials.
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post #66 of 112
12/21/06 at 11:50am
Thread Starter 
Quote:
Originally Posted by drarthurwells View Post

Your system's source jitter, and other colorations in your sysem, could mask the differences making discrimination difficult between the jitter-free and jitter-containing materials.
Ah, the your stereo isnt good enough to hear the difference clause, I was wondering when that would rear its head again and bang on cue. Of course if I come back and say I do hear jitter you wont say - no you couldnt your stereo isnt good enough.

If added jitter is a problem any competent system should show it up, if it isnt the best system in the world will not. You are obviously worried that I wont hear any difference and are getting the excuses in early, next will be my hearing ability, my taste in music and my training.

Lets recap the study

The experimenters used a computer based system - such systems supposedly less prone to the jitter inducing issues plagued by normal CD systems, thus they could produce a signal with very very low levels of jitter Audioeng himself uses such systems and implies that they are in fact better in jitter terms. His 3:4 test is predicated on this assumption.

Then the experimenters added high levels of jitter to determine at what point it became audibly perceptible. Using their own kit and music they know nobody (inc musicians and audio pros) in blind tests could detect added jitter until it was between 250 and 500 ns. Are you serioulsy suggesting that anybody has discriminative abilities that are 2500 times better i.e enough to detect 100ps. By that premise the Wow and flutter in turntables of even 0.02% i.e several hundred microseconds would be grotesquely unlistenable for these listeners.
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post #67 of 112
12/21/06 at 3:51pm
Quote:
Originally Posted by hciman77 View Post
Cheers, and I will happily pay postage and materials costs. If you could send me a normal copy and a jitter-reduced copy but just mark them A and B, thanks. Bung me your paypal address and I will send you some cash.
Better yet, if you already have one of these:

Nora Jones - come away with me (best)
Miles Davis - Kind of Blue

Then I can just send you the copy.

nugent@empiricalaudio.com is my PayPal address

Steve N.
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post #68 of 112
12/21/06 at 4:29pm
Thread Starter 
Quote:
Originally Posted by audioengr View Post
Better yet, if you already have one of these:

Nora Jones - come away with me (best)
Miles Davis - Kind of Blue

Then I can just send you the copy.

nugent@empiricalaudio.com is my PayPal address

Steve N.
I have ordered a copy of

Nora Jones - come away with me (best)

from Amazon, sadly it wont be hear until after Christmas, how much do you want for shipping ?

This should be interesting. I have two transports feeding a DAC, I will get the wife to load the two CDs into the transports without telling me which is in which and I will switch betwen the two blind. Alternatively I have a changer and I can get the missus to load two adjacent slots but this will introduce a delay.

I will listen to the commercial CD a few times first to get ued to the sound.

I must be honest and say that Jazz really is not one of my normal listening choices, I generally listen to "Classical" and lately a lot of Lute music from John Dowland and contemporaries. I offer this in the spirit of disclosure, though if the effect of jitter is pronounced this should not be an issue.

Why did you choose that particular CD incidentally ? - I would have gone for Mehta's 1975(?) Mahler 2 which has a tremendous dynamic range and is a superb recording for such an old performance.

Regarding your jitter-free copy, I could not get the same reduction from a 1X speed secure rip using EAC and 1X burn and a good quality CD-R ? - just asking.
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post #69 of 112
12/21/06 at 4:58pm
Quote:
Originally Posted by Audioengr
There are no bit errors with my CD's. Very clean, treated and no scratches. The Transport PLL reacts to the changing bit-rate from the disk read and jitter is the result. If you dont believe me, I can ship you a rewrite so you can hear the difference yourself.
Hi Steve,

I am really amazed this keeps coming up. Modern players do not use a PLL to impact the output clock in any way. They use a stable crystal oscillator to drive the DACs and the output and feed that same clock to the laser assembly controller.

The disc spins and is being read completely asynchronously to this master clock. Pit jitter has no impact on the output clock in a contemporary CD player. Even all lowly in-dash players in cars work exactly this way. I am a bit pressed for time otherwise I would repost the link to the Philips CD chipsets that are being used to implement most CD players. They have this feature till 1995.

This tigtht coupling to a local clock is one of the reasons why it is harder to make an external DAC sound as good as a standalone player. The external DAC usually needs to synchronize on the incoming digital signal and that is where all your good work on low jitter comes in but it does not apply for most current CD players.

Cheers

Thomas
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post #70 of 112
12/21/06 at 5:05pm
Thread Starter 
Quote:
Originally Posted by thomaspf View Post
Hi Steve,

The disc spins and is being read completely asynchronously to this master clock. Pit jitter has no impact on the output clock in a contemporary CD player. Even all lowly in-dash players in cars work exactly this way. I am a bit pressed for time otherwise I would repost the link to the Philips CD chipsets that are being used to implement most CD players. They have this feature till 1995.
Now you tell me

I have just ordered a copy of a Jazz CD to test this out and I dont even particularly like Jazz !
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post #71 of 112
12/21/06 at 5:23pm
At least Jazz is audible!

See ya
Steve
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post #72 of 112
12/21/06 at 5:32pm
But that doesn't mean it exists...
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post #73 of 112
12/21/06 at 7:28pm
Thread Starter 
Quote:
Originally Posted by trains are bad View Post
But that doesn't mean it exists...
Ah the Zen paradox.

Like...

'If a tree falls in a forest, and no one's around to hear it, and it falls on a mime, does anyone care?' - Gary Larson, The Far Side

or

The dungeons of the palace held a number of felons imprisoned "at his lordship's pleasure", and since Lord Vetinari was seldom very pleased they were generally in for the long haul. The notable exception to this rule are mimes, who Vetinari despises for some unknown reason. Vetinari banned all mime performances from Ankh-Morpork shortly after taking power. Mimes who violate the ban usually find themselves trying to climb invisible ladders out of Vetinari's scorpion pit whilst reading a sign saying 'learn the words.' - Terry Pratchett
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post #74 of 112
12/21/06 at 7:51pm
Quote:
Originally Posted by hciman77 View Post
I have just ordered a copy of a Jazz CD to test this out and I dont even particularly like Jazz !
Had you ordered Kind of Blue, you would at least have Steve to thank for turning you on to a good album. Norah Jones comes in handy occasionally, tho.
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post #75 of 112
12/21/06 at 7:53pm
Quote:
Originally Posted by thomaspf View Post
Hi Steve,

I am really amazed this keeps coming up. Modern players do not use a PLL to impact the output clock in any way. They use a stable crystal oscillator to drive the DACs and the output and feed that same clock to the laser assembly controller.

The disc spins and is being read completely asynchronously to this master clock. Pit jitter has no impact on the output clock in a contemporary CD player. Even all lowly in-dash players in cars work exactly this way. I am a bit pressed for time otherwise I would repost the link to the Philips CD chipsets that are being used to implement most CD players. They have this feature till 1995.

This tigtht coupling to a local clock is one of the reasons why it is harder to make an external DAC sound as good as a standalone player. The external DAC usually needs to synchronize on the incoming digital signal and that is where all your good work on low jitter comes in but it does not apply for most current CD players.

Cheers

Thomas
Thomas - the offer is for you as well. I'll be happy to send you a copy of either of these disks. Just email your shipping address to me and which of the two disks.

Steve N.
Empirical Audio
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