Luke's "are identical CDs identical?" thread

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Postby Crummy Old Label Avatar » Sat Mar 18, 2006 5:56 pm

I have a Pioneer Elite PD65 that can play anything you can throw at it EXCEPT those Black CD-Rs. No matter the brand or burning speed, the black discs choke it always. Given that the big claim about the black discs has always been that they "track more easily" than other discs, I always found this strange.

Every other player (portable Discman, car stereo, 3 different DVD players) I've ever put these into has never exhibited any problems whatsoever.

We all have stories like this, I'm certain. No big revelation, surely, but if you have confirmed that you have a proper rip and error-free burn already, that's tangible, postiive proof that the player itself is the culprit.

However, I wouldn't underestimate user ignorance. I'd be willing to bet that the majority of people DO NOT have EAC or cdda2wav or whathaveyou set up properly, have never run simple tests to make sure their burner is properly configured, etc. Nor are they willing to learn how to do so.

(And if you think I'm just taking cheap shots, Andreas, need I remind you of some of the other laughable claims being made by the likes of Grant and Dave Night Goof, such as "purchased songs from the iTunes music store will only play a certain number of times before disappearing" and "gold CDs sound better than aluminum and I can hear the difference"?

What these two have demonstrated time and again is that they suffer from incomprehension -- not to mention an utter inability to digest basic information; my guess is that their ripping/burning setup is as half-assed as any of their half-baked "theories".)

You can't have cockamamie elitism without pricy obscurantism. False consciousness always wins in these "audiophile" debates: the $1000 cable MUST be better than the $10 interconnect at Home Depot, the MOFI CD-R has got to be better than the TDK disc from (gasp) Taiwan. After all, it has a MOFI logo on it! It costs 10 times more than "lesser" CD-Rs! It'll clear up those cloudy transients!

Luke wrote:Without a trial once and for all that would prove that differences are just in people's heads, I'm not going to make that claim


OK, then I will. How is this any different from their cable claims, their green marker claims, their Shakti stone voodoo, the jitter boogieman.................. ? With a track record like that, I'd err on the side of their proven nuttiness.
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Postby lukpac » Sat Mar 18, 2006 6:15 pm

Crummy Old Label Avatar wrote:OK, then I will. How is this any different from their cable claims, their green marker claims, their Shakti stone voodoo, the jitter boogieman.................. ? With a track record like that, I'd err on the side of their proven nuttiness.


Well, like I said, at least one person I trust has heard differences - or at least has thought he has.

And really, as much as I'm eager to discount all of that other voodoo, has any of it been tested? Either via A/B/X tests or some type of spectral analysis?

Check out figures 7 and 8 in the Prism article. 7 is using the DAC in the CDP, while 8 is using an external DAC. Lots of extra garbage when using the CDP's DAC. The only thing I'm *not* certain of is how much that changes depending on the discs used. Wait, never mind:

Figures 11. and 12. show the same two test tracks but using a different disc from the set. Note that the behaviour of the 390Hz-spaced components is the same as for the other disc, and varies identically with track position. The low-frequency components, on the other hand, are characteristic of the disc and vary only slightly with the track position.

Neither component type was reproducible with an external DAC, regardless of the jitter-rejection capabilities of the DAC.

The track-position-dependent and disc-dependent components were investigated further using the DC test track, with the analogue output of the player connected through an analogue band-pass filter to an oscilloscope.

By tuning the band-pass filter to 390Hz, the modulation source was seen to be a 390Hz signal which was being rapidly switched on and off. The duty-cycle of the switching was directly dependent on the track position on the disc. It was conjectured that the 390Hz-spaced modulation components were related to the player's motor-control servo.

By tuning the band-pass filter over the 10Hz-100Hz region, it was possible to investigate the disc-dependent components. In this case it was necessary to capture the output on a storage oscilloscope. The technique employed was to start the DC track and allow a fixed period of time to elapse for the system to stabilise after the beginning of the DC output, before capturing a few seconds of output on the oscilloscope. This was found to produce a characteristic pattern for each disc. It was inferred that the low-frequency modulation components were related to the player's tracking and/or focusing servos.

The extent and precise characteristics of the servo-related modulation components varied considerably from player to player.

It appears on the basis of superficial investigation that the nature of the disc-related components does not correlate noticeably with the manufacturing variables; i.e. they are not repeatable from set to set.

None of the disc-related or servo-related artifacts was present for any two-box system: jitter-rejecting DACs were generally clean, as shown in the figures, whereas the spectra of non-jitterrejecting DACs were swamped with interface-jitter-induced components which were large in comparison to the artifacts noted above in one-box players.

The existence of the above-mentioned amplitude modulation components in one-box players have since been independently corroborated by other investigators [5].


While blind tests may not yet be conclusive, it sure looks like there is *some* scientific evidence to indicate that players *can* make digitally identical discs produce different sounds.
"I know because it is impossible for a tape to hold the compression levels of these treble boosted MFSL's like Something/Anything. The metal particulate on the tape would shatter and all you'd hear is distortion if even that." - VD

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Re: Luke's "are identical CDs identical?" thread

Postby krabapple » Sat Mar 18, 2006 6:44 pm

Ah, the Dennis & Dunn paper that helped spawn my avatar here back in early '04. A shame Dunn died, no one seems to have taken up the banner for research into audibility of jitter since then (AFAIK, he never nailed down what the audible level was. Hence the invocation of 'jitter' remains the audiofool's last, best, yet most predictable defense against reality)

Interestingly, when I asked Stewart Pinkerton about this paper, he seemed to be of the opinion that it was outdated, and it was more likely now that CD separates would be more prone to audible difference (such little as may exist), than one-box unit.

I've more recently come to believe that many CD/DVD player differences may simply be mismatched levels in output stages and/or different settings. I could make the output clip on one of my players simply by setting the channel level menu to 'FIXED', which gave every channel a +6 dB boost.
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Postby krabapple » Sat Mar 18, 2006 6:53 pm

lukpac wrote:
Andreas wrote:Not if the uncorrectable data errors occur at a continuous rate and force the CD player to interpolate frequently.

A burned CDR has more physical errors than a factory-pressed CD. The faster the burning speed, the more physical errors.


Any source for this? I don't want to say "I don't believe you", but I don't believe you.

If you extract the CD with a program like EAC, these physical errors can be corrected accurately, since it reads each stream twice and has enough time to slow down the reading speed. Therefore, the burned CDR will still be bit-identical to the original.

However, a CD player does not have the possibility to slow down if necessary or to read error-laden parts twice.


I get bit-accurate rips at higher than 16x extraction. Even with all of EAC's "stuff" turned on (which I often don't use anyway), I always get something faster than 1x overall (more like 4x or 8x or something). Which means the disc is spinning a lot faster than that. Why would a standalone player have more problems at 1x?

If the errors add up and can't be corrected by the Reed-Solomon-Cross-Interleaved Code anymore, the CD player will use interpolation to avoid skipping or stalling. This interpolation is audible, and it can affect things like the definition of the bass, the clarity of the highs, the soundstage or transients. Therefore, the CDR can sound different from the original CD, even if it is bit-identical.


If the errors really "add up" in the way you are describing, I would think there would be far more than would be able to be interpolated, and you'd actually end up getting clicks and such. What are the odds that these errors would just happen to be too large to actually correct but not large enough that they can't be interpolated?


This has been hashed ut in detail over at hydrogenaudio.org. IIRC the result was that some drives work 'best' (fewest errors) at faster speeds, some not. I don't think Andreas' scenario was supported.

HA might be a better place to run all this by, btw. You'd be surprised at some of the big tech brains that come out of hiding when topics like these show up.
Last edited by krabapple on Sat Mar 18, 2006 6:56 pm, edited 1 time in total.
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Postby krabapple » Sat Mar 18, 2006 6:56 pm

Andreas wrote:
lukpac wrote:Any source for this?

It's a theory. A theory has no source, because then it would be a fact.


Wrong. In science a theory is a very well-supported model; it's actually a rather lofty level for any idea to attain. What your propose is more like a hypothesis -- or, since it isn't based on any known facts other than the 'observation' that some people, in sighted listening, think bit-identical CDs sound differemt, closer to sheer speculation.
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Postby krabapple » Sat Mar 18, 2006 7:24 pm

here's an interesting HA thread on jitter

http://www.hydrogenaudio.org/forums/ind ... opic=11909
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Re: Luke's "are identical CDs identical?" thread

Postby lukpac » Sat Mar 18, 2006 9:39 pm

krabapple wrote:Ah, the Dennis & Dunn paper that helped spawn my avatar here back in early '04. A shame Dunn died, no one seems to have taken up the banner for research into audibility of jitter since then (AFAIK, he never nailed down what the audible level was. Hence the invocation of 'jitter' remains the audiofool's last, best, yet most predictable defense against reality)


Eh? Pretty much everything I've seen says different CDs *don't* produce differences in jitter, that paper included.

Interestingly, when I asked Stewart Pinkerton about this paper, he seemed to be of the opinion that it was outdated, and it was more likely now that CD separates would be more prone to audible difference (such little as may exist), than one-box unit.


Any idea why? How could any differences make it through the digital stream from one piece of equipment to another? That paper showed that the differences in single box equipment didn't exist in separates.
"I know because it is impossible for a tape to hold the compression levels of these treble boosted MFSL's like Something/Anything. The metal particulate on the tape would shatter and all you'd hear is distortion if even that." - VD

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Postby lukpac » Sat Mar 18, 2006 9:54 pm

krabapple wrote:here's an interesting HA thread on jitter

http://www.hydrogenaudio.org/forums/ind ... opic=11909


Interesting, although I don't see anything about differences in digitally identical CDs causing different amounts of jitter...
"I know because it is impossible for a tape to hold the compression levels of these treble boosted MFSL's like Something/Anything. The metal particulate on the tape would shatter and all you'd hear is distortion if even that." - VD

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Postby Xenu » Sat Mar 18, 2006 11:05 pm

The thread's on again at sh.tv. I've had my fill of Sisyphusian ordeals for one week.
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Re: Luke's "are identical CDs identical?" thread

Postby krabapple » Sun Mar 19, 2006 12:25 am

lukpac wrote:
krabapple wrote:Ah, the Dennis & Dunn paper that helped spawn my avatar here back in early '04. A shame Dunn died, no one seems to have taken up the banner for research into audibility of jitter since then (AFAIK, he never nailed down what the audible level was. Hence the invocation of 'jitter' remains the audiofool's last, best, yet most predictable defense against reality)


Eh? Pretty much everything I've seen says different CDs *don't* produce differences in jitter, that paper included.


um...OK, and *I'm* saying that audiofools will keep invoking jitter regardless.

I'm *agreeing* with you, Luke.

Interestingly, when I asked Stewart Pinkerton about this paper, he seemed to be of the opinion that it was outdated, and it was more likely now that CD separates would be more prone to audible difference (such little as may exist), than one-box unit.


Any idea why? How could any differences make it through the digital stream from one piece of equipment to another? That paper showed that the differences in single box equipment didn't exist in separates.



I'd have to go back and look for Stewart's post, but on that HA jitter thread, there is some mention of why *modern* (as of 2003) one-box players would not be expected to display DAC jitter.

The Dunn and Dennis work was from 1996, btw.
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Postby thomh » Sun Mar 19, 2006 4:39 am

David,

I saw that you brought up the ol' jitter article by Roger Nichols over on SHtv: http://stevehoffman.tv/forums/showpost. ... tcount=102

For the record, that little mess was cleared up some time ago and your hunch that Roger was "hearing things" was not too far off:

http://www.3daudioinc.com/3db/showpost. ... stcount=46
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Re: Luke's "are identical CDs identical?" thread

Postby lukpac » Sun Mar 19, 2006 8:56 am

krabapple wrote:um...OK, and *I'm* saying that audiofools will keep invoking jitter regardless.

I'm *agreeing* with you, Luke.


Sorry, I wasn't following.
"I know because it is impossible for a tape to hold the compression levels of these treble boosted MFSL's like Something/Anything. The metal particulate on the tape would shatter and all you'd hear is distortion if even that." - VD

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Postby lukpac » Sun Mar 19, 2006 8:59 am

thomh wrote:For the record, that little mess was cleared up some time ago and your hunch that Roger was "hearing things" was not too far off:

http://www.3daudioinc.com/3db/showpost. ... stcount=46


?

That guy invokes jitter regarding CD audio. He mentions "faulty equipment" but doesn't go any farther.
"I know because it is impossible for a tape to hold the compression levels of these treble boosted MFSL's like Something/Anything. The metal particulate on the tape would shatter and all you'd hear is distortion if even that." - VD

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Postby lukpac » Sun Mar 19, 2006 9:59 am

BTW...I took Grant's "test" last night. Compared a 48x burn (BBE off of the SH Who's Next) to the pressed CD. Switched back and forth between two CD players. I thought *maybe* I heard a difference, but then...no. I switched the discs around, and I'm pretty sure the only difference is one CDP is ever so slightly louder than the other.

Oh, wait, I didn't burn at *52x*. *That* must be the difference.
"I know because it is impossible for a tape to hold the compression levels of these treble boosted MFSL's like Something/Anything. The metal particulate on the tape would shatter and all you'd hear is distortion if even that." - VD

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Postby Andreas » Sun Mar 19, 2006 10:02 am

"Sheer speculation"

It doesn't really matter, but I am a scientist. I know what a THEORY is. But I also have about 200 "theories", most of which are probably false or wrongly stated. This use of the word "theory" in every day language is so common, even among scientists. That I get called for that on a fun-and-hobby-forum like this one is quite ridiculous.

Of course, I cannot develop a THEORY about perceived differences between bit-identical CDs, because that is not my research area. D'oh! But neither can the specialists, as it seems. Unless the explanation is "listener bias", which is another "sheer speculation".