serengetiplains said:
Sure, that is possible, in theory. I don't know the relative magnitude of the influence so I have no opinion on whether it actually is possibly audible. The effect may be below the generally accepted limit for audible jitter, or it may be above it, I have no clue about that.
But the discussion was on error correction, no? Or did I miss a subtle redirection of the last few days?
Jan Didden
Agreed. Again, I remain skeptical that such jitter levels as produced by moderate disc vibration would have a readibly audible effect, but I do remain open to the possibility. It is universally accepted that jitter is audible after some level. The question is at what level, for what frequency components, and is this above or below the level produced by consumer CD players under moderate vibration.
However Thorsten has attempted to pin the effect on error correction -> error concealment shifts, and for this explanation I remain more than skeptical.
However Thorsten has attempted to pin the effect on error correction -> error concealment shifts, and for this explanation I remain more than skeptical.
Steve, I think you're twisting John's reference to jitter. My sense is he was saying the high end audio community, for its purposes, discovered that jitter had audible effects. I don't think he was saying, or at least I didn't read him to say, the high end audio community can claim a "discovery." That wasn't his point.
RHosch said:
With good reason.
Unless you have an unusually bad disc, and/or an unusually ill-designed player, the typical number of uncorrectable errors you'll get with a decent disc on even a very modest player you can count on your fingers and toes and still have a few left over.
I'm surprised this issue is still being brought up today. This issue had been well settled back in the 80s.
Most CD chipsets have C1 and C2 error flag pins. If you want to see how your player does with regard to uncorrectable errors, just monitor the C2 fail pin.
This was done by a number of folks back in the 80s (on the old CompuServe CEFORUM). I even built a little counter circuit to count the errors on one person's player (my player at the time had a Yamaha chipset which didn't have any external error flag pins).
Bottom line, uncorrectable errors are rare.
se
Steve Eddy said:
I remember a construction article in Elektor many years ago of what was basically a digital counter counting the corrected errors over the playing time of a disc. It was tapping some signals from the CD player digital section.
IIRC there were literally THOUSANDS of corrected errors within the hour or so it took the disc to play. Error correction is not a safety measure, it is absolutely essential to have a usable replay medium. And remember, those thousands of errors are corrected 100% and caused ZERO misread bits.
Jan Didden
The pointy legs on a CD were the original reason why this discussion got sent in this direction. I was taking issue with Peter Daniel and his rather obscenely overengineered $200+ case for $60 worth of audio kit with pointy legs on it.
This lead to indirectly to this topic of the DACs and pointy legs.
Between themselves the various golden ears come up with all sorts of theories why various elaborate / expensive tweaks sound better, and they eventually become gospel. So they take these utterly extreme measures to isolate vibrations from a CD player, as if it is affected by acoustic feedback like a record turntable.
Now that the error-correction misunderstanding has been thoroughly trampled into the ground as an explanation for the audio effects they claim are there, up comes yet another theory to explain sonic effects caused by pointy feet and other even more elaborate tweeks.
So now it is feedback-induced jitter as the pet theory. This one is a bit harder to prove wrong, but I think I can do it. Many of the same proponents also believe that freezing their CDs makes a difference in the playback, but now that we have utterly and completely demolished the argument that small errors occur when CDs are played back, there is no mechanism for a freezed CD to affect the sound in any way.
The Cryo'ed CD simply could not have an effect on jitter, since the error correction would read EXACTLY the same digital stream into the DAC. Or really, really big errors. There is no in-between.
I found a very authoratative article about quartz oscillators:
http://www.us.anritsu.com/downloads/files/freq_accuracy.pdf
So I did calculations based on the short term accuracies stated in the article. Long term accuracy does not matter so much, because you are not going to have the temperature changing hardly at all during a listening session, or any significant aging of the quartz crystal happening during that time.
I did the following calcs in Excel:
I really think you must have astonishing ears if you can hear jitter at 0.00002 hz.
This lead to indirectly to this topic of the DACs and pointy legs.
Between themselves the various golden ears come up with all sorts of theories why various elaborate / expensive tweaks sound better, and they eventually become gospel. So they take these utterly extreme measures to isolate vibrations from a CD player, as if it is affected by acoustic feedback like a record turntable.
Now that the error-correction misunderstanding has been thoroughly trampled into the ground as an explanation for the audio effects they claim are there, up comes yet another theory to explain sonic effects caused by pointy feet and other even more elaborate tweeks.
So now it is feedback-induced jitter as the pet theory. This one is a bit harder to prove wrong, but I think I can do it. Many of the same proponents also believe that freezing their CDs makes a difference in the playback, but now that we have utterly and completely demolished the argument that small errors occur when CDs are played back, there is no mechanism for a freezed CD to affect the sound in any way.
The Cryo'ed CD simply could not have an effect on jitter, since the error correction would read EXACTLY the same digital stream into the DAC. Or really, really big errors. There is no in-between.
I found a very authoratative article about quartz oscillators:
http://www.us.anritsu.com/downloads/files/freq_accuracy.pdf
So I did calculations based on the short term accuracies stated in the article. Long term accuracy does not matter so much, because you are not going to have the temperature changing hardly at all during a listening session, or any significant aging of the quartz crystal happening during that time.
I did the following calcs in Excel:
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An externally hosted image should be here but it was not working when we last tested it.
I really think you must have astonishing ears if you can hear jitter at 0.00002 hz.
Thanks 'sere' of course I was talking about the importance of jitter to audio quality. In my day, we had Wow and Flutter, this was a problem with analog recording and a real problem with FM recording. I'm sure the military-industrial complex and the telephone company had lots to say on the subject, BEFORE we got interested in it.
geewhizbang said:
Hey, nice graphics. Are you perchance a graphics designer? Imagine that ole fool Meitner believing what he believes! I think I need a beer!
serengetiplains said:
Bell Labs.
Hell, where do you think the linear pulse code modulation (LPCM) scheme that Compact Disc uses came from? It was created by Bell Labs in the 1940s and the effects of timing jitter were being considered even before any sort of LPCM system could be implemented.
Most people simply aren't aware of how much "audio" technology has come from the telecommunications industry, and most of that from Bell Labs.
If you have a good library nearby, paritcularly a good university library with a good reference section, see if they have any of the old Bell Labs technical bulletins and publications from the 1930s, 40s and 50s.
se
Stop scratching your CD's, if it's such a problem.Kuei Yang Wang said:
Indeed. A lot of IFs. It all sounds a bit iffy to me.
I'm not questioning that vibration might increase drive current demands, and thus induce jitter in the clock circuit. I have no reason to doubt that. However, with all these vibration issues, I'd simply suggest relocating the dang CD player to another room!
Why insist on having it a wavelength away from the loudspeakers?
As far as error concealment is concerned, it is truly alarming if it happens so often that it's noticed not as occasional glitches, but rather as a more or less continous sound degradation. What rate are you measuring? One every 10 samples? One every second? One on every track? One on every CD?
Rune
janneman said:
Yeah. Far as I'm aware, even the earliest Philips CD decoder chipsets had external C1 and C2 error flag pins. You just have to monitor the C2 pin for a C2 failure, which means an uncorrectable error.
Exactly.
Uncorrectable errors are very rare. This is old news. Which is why I'm surprised that some are still trying to make an issue of it.
se
The only reason I can think of that would make cryo work is that the disc gets som better physical properties like weigth (neee) or symetry (more round, flatter) and thus, causing less vibration itself.
geewhizbang, I can't relate to the figures but jitter end up as frequency response errors in the analouge domain !
Maybe that could explain something ....
/
geewhizbang, I can't relate to the figures but jitter end up as frequency response errors in the analouge domain !
Maybe that could explain something ....
/
I'm a graphic designer, web page designer, computer programmer, odd job repairs, computer consultant. I wear a lot of different hats and get the bills paid one way or another.
The table is just a cropped print screen copy of the excel table, btw.
I also have a master's in Mechanical Engineering. This is almost the same thing as a degree in Physics, except the emphasis is on application rather than research.
I am also somewhat of an audio nut too. Mostly I build my own speakers, but I am trying to branch out to see what I can do with more complex things like amplifiers.
There is both a stunning amount of really good ideas on this site and an abundance of totally absurd pseudoscience. I am not interested in wasting on things that make no sense based on the laws of physics.
I am not so easily awed by psuedoscience as so many here, so I like this current thread. I'm a big fan of Randi in the first place.
And yes, Meitner is just blowing hot air. He does it quite well, but he is just full of ... you know what.
The table is just a cropped print screen copy of the excel table, btw.
I also have a master's in Mechanical Engineering. This is almost the same thing as a degree in Physics, except the emphasis is on application rather than research.
I am also somewhat of an audio nut too. Mostly I build my own speakers, but I am trying to branch out to see what I can do with more complex things like amplifiers.
There is both a stunning amount of really good ideas on this site and an abundance of totally absurd pseudoscience. I am not interested in wasting on things that make no sense based on the laws of physics.
I am not so easily awed by psuedoscience as so many here, so I like this current thread. I'm a big fan of Randi in the first place.
And yes, Meitner is just blowing hot air. He does it quite well, but he is just full of ... you know what.
If such jitter is being caused, then in the usual five minute track we have:
0.00002 cycles/second (hz) x 5 minutes x 60 seconds/minute = .006 cycles in the average song. Now if there is a frequency domain effect from that I'd be really surprised.
I really though those that were talking about significant microphonic effects were blowing hot air in the first place. Quartz oscillators are very very precise, especially in the short run. Over the longer run, they do have problems with temperature and age-related drift, so they have to be recalibrated against atomic clocks for very high accuracy measurements, but we are talking parts per billion here.
0.00002 cycles/second (hz) x 5 minutes x 60 seconds/minute = .006 cycles in the average song. Now if there is a frequency domain effect from that I'd be really surprised.
I really though those that were talking about significant microphonic effects were blowing hot air in the first place. Quartz oscillators are very very precise, especially in the short run. Over the longer run, they do have problems with temperature and age-related drift, so they have to be recalibrated against atomic clocks for very high accuracy measurements, but we are talking parts per billion here.
I'm with Kuei here
No it won't.
You obviously don't understand how this works. There is a BIG difference between getting the data from the disc (which a non-real time process, like a PC copy can do repeatably) and actually playing the disc, in real time for music.
They are NOT the same thing.
Mark Levinson, Naim Audio, Wadia, Chord Electronics and no doubt others go to great efforts to re-clock this data because it makes a difference, it is, in essence, synchronous.
Try looking up phase noise and jitter in oscillators, you may learn something!
They are very stable, but not sufficiently so to prevent degradation in the analogue performance of a DAC, unless very well designed.
Clock jitter and the analogue domain are directly related in a DAC. single digit picoseconds of jitter are audible.
Andy.
No it won't.
You obviously don't understand how this works. There is a BIG difference between getting the data from the disc (which a non-real time process, like a PC copy can do repeatably) and actually playing the disc, in real time for music.
They are NOT the same thing.
Mark Levinson, Naim Audio, Wadia, Chord Electronics and no doubt others go to great efforts to re-clock this data because it makes a difference, it is, in essence, synchronous.
Try looking up phase noise and jitter in oscillators, you may learn something!
They are very stable, but not sufficiently so to prevent degradation in the analogue performance of a DAC, unless very well designed.
Clock jitter and the analogue domain are directly related in a DAC. single digit picoseconds of jitter are audible.
Andy.
Konnichiwa,
NO.
I clearly stated that such vibrations, if they caused a sufficiently high degree of error would cause the Error Correction to interpolate samples. This was a slight misstatement, as error correction and interpolator are seperate items. However, they operate as one functional unit as the interpolator is invoked by the error correction if the error correction fails to correct the errors.
Now I may be guilty os a modest semantic error, namely of cobining error correction and error concealement into one, but I would posit that besides semantics there is no issue.
Absolutely. If you actaulally bothered to read what i had written that would be clear. But have you ever attached a LED to the "error flag" output of the Decoder IC (if present)? You would be surprised how often and how brightly this can light, even with factory new CD's indicating an error that could not be corrected.
Interpolation between two adjecent samples is unlikely to be VERY audbile. It is likely however that it will be SOMEWHAT audible. Even the repeat of one sample in place several of the 22.7uS long samples MAY not be grossly audible, depending upon the musical passage it may in fact remain inaudible if one has no direct comparison to a source that is not subject to the same error.
So, the two go very much hand in hand and the states between "No Error" and "grossly audible error" are fluid, not a "digital" state.
Repeating your claims again and again, even in the light of clear proof from philips own datasheets to the contrary insults the intelligence of all readers and shows your own actual understanding in a rather bad light.
In case you failed to notice, I ALREADY GOT AWAY WITH IT.
I have already posited PROOF that error correction and concealement work together in EXACTLY the fashion I described.
Anyone who has seen the Eye pattern on a CD being vibrated (like by the workshop system) will not argue that there CANNOT be any influence.
How large this is and how audible is another story.
My point was merely that if we postulate audible differences for different footers under CD Players (and I must say that I observe such differences) the mechanism I suggested MAY be one of them, together with microphonics in the Clock crystal, in Capacitors and in C-Mos Chips, analogue and digital.
So, IF pointy feet change the resonance behaviour of the Player placed upon them (the fact of them being pointy or not is not my point BTW - most other "feet" can operate similarly - I prefer wooden disks over anything pointy in most cases) then mechanisms exist that MAY lead to audible differences.
Hence anyone claiming that there is NO LOGICAL POSSIBILITY is severely ignorant or deluded. That was my point and again, i would argue that it has been proven in the context of the argument.
Now the argument says nothing about what is the source of Peter Daniels experiences with pointy feet. It does not claim that any, all or even different mechanisms cause the differences he observes or indeed if such differences are purely imaginary and the result of mass hypnosis by the manufacturers of pointy feet.
The argument is merely that an outright dismissal is unscientific.
I believe that in that particular sense the argument has been made sufficiently.
I had a very early front loading, vertical CD Player that actually had an Error LED (I believe a badged Yamaha or Sony). This would show the Error Flag from the decoder board. Even after a full service, alignment and all some bandnew CD's would illuminate the LED almost permanently. I did not per se notice any drastic audible changes and never really invetigated further, the whole sounded pretty bad anyway. I needed it however to get me through my second degree at university in the mid 1990's.
Actually, I did nbot state that ALL new CD's cause more errors than can be corrected, I noted merely that I had some which in a case where the "error" was easily observed I observed them even with some barndnew and unscratched CD's. Not all, not most, but some.
No, I can live with that. DVD Players MAY be a seperate case, especially "low grade" ones as they often combine the DVD and CD Replay into one servo processo etc, leading to asyncronous Read on CD, as this is the way DVD works all the time. So, in such a player the Bitaccuracy may indeed be high even in poor conditions.
For the rest, shall we say that in your circumstances you did not observe much?
Did you find in CD's with largaer number of micro scratches that the "single sample interpolation" events where independent of the soundfield the player was exposed to or not?
I have since regulary observed that on my rather more sophisticated replay gear CD's that are fairly scratched sound rather "bad", hazy, as i some low level resolution is gone. I have aso found that these CD's can be rescued by ripping them to HD using EAC in paranoid mode (it tends to take a long time to rip) and then recording it on a new CD.
These are extreme cases and note that I did not posit the Vibration/Error Correction as THE EXPLANATION, but as a possible one.
Now, would consider that if the resonance behaviour of a CD player was changed and a CD with a large number of micro scratches (often invisible to the naked eye) was played that an audible effect MAY be possible, which is what I suggest, or do you feel that you can exclude the above suggested effect in the above suggested circumstances reliably to the point of saying "It cannot logically happen"?
Sayonara
janneman said:
NO.
I clearly stated that such vibrations, if they caused a sufficiently high degree of error would cause the Error Correction to interpolate samples. This was a slight misstatement, as error correction and interpolator are seperate items. However, they operate as one functional unit as the interpolator is invoked by the error correction if the error correction fails to correct the errors.
Now I may be guilty os a modest semantic error, namely of cobining error correction and error concealement into one, but I would posit that besides semantics there is no issue.
janneman said:
Absolutely. If you actaulally bothered to read what i had written that would be clear. But have you ever attached a LED to the "error flag" output of the Decoder IC (if present)? You would be surprised how often and how brightly this can light, even with factory new CD's indicating an error that could not be corrected.
janneman said:
Interpolation between two adjecent samples is unlikely to be VERY audbile. It is likely however that it will be SOMEWHAT audible. Even the repeat of one sample in place several of the 22.7uS long samples MAY not be grossly audible, depending upon the musical passage it may in fact remain inaudible if one has no direct comparison to a source that is not subject to the same error.
So, the two go very much hand in hand and the states between "No Error" and "grossly audible error" are fluid, not a "digital" state.
janneman said:
Repeating your claims again and again, even in the light of clear proof from philips own datasheets to the contrary insults the intelligence of all readers and shows your own actual understanding in a rather bad light.
In case you failed to notice, I ALREADY GOT AWAY WITH IT.
I have already posited PROOF that error correction and concealement work together in EXACTLY the fashion I described.
Anyone who has seen the Eye pattern on a CD being vibrated (like by the workshop system) will not argue that there CANNOT be any influence.
How large this is and how audible is another story.
My point was merely that if we postulate audible differences for different footers under CD Players (and I must say that I observe such differences) the mechanism I suggested MAY be one of them, together with microphonics in the Clock crystal, in Capacitors and in C-Mos Chips, analogue and digital.
So, IF pointy feet change the resonance behaviour of the Player placed upon them (the fact of them being pointy or not is not my point BTW - most other "feet" can operate similarly - I prefer wooden disks over anything pointy in most cases) then mechanisms exist that MAY lead to audible differences.
Hence anyone claiming that there is NO LOGICAL POSSIBILITY is severely ignorant or deluded. That was my point and again, i would argue that it has been proven in the context of the argument.
Now the argument says nothing about what is the source of Peter Daniels experiences with pointy feet. It does not claim that any, all or even different mechanisms cause the differences he observes or indeed if such differences are purely imaginary and the result of mass hypnosis by the manufacturers of pointy feet.
The argument is merely that an outright dismissal is unscientific.
I believe that in that particular sense the argument has been made sufficiently.
RHosch said:
I had a very early front loading, vertical CD Player that actually had an Error LED (I believe a badged Yamaha or Sony). This would show the Error Flag from the decoder board. Even after a full service, alignment and all some bandnew CD's would illuminate the LED almost permanently. I did not per se notice any drastic audible changes and never really invetigated further, the whole sounded pretty bad anyway. I needed it however to get me through my second degree at university in the mid 1990's.
RHosch said:
Actually, I did nbot state that ALL new CD's cause more errors than can be corrected, I noted merely that I had some which in a case where the "error" was easily observed I observed them even with some barndnew and unscratched CD's. Not all, not most, but some.
RHosch said:
No, I can live with that. DVD Players MAY be a seperate case, especially "low grade" ones as they often combine the DVD and CD Replay into one servo processo etc, leading to asyncronous Read on CD, as this is the way DVD works all the time. So, in such a player the Bitaccuracy may indeed be high even in poor conditions.
For the rest, shall we say that in your circumstances you did not observe much?
Did you find in CD's with largaer number of micro scratches that the "single sample interpolation" events where independent of the soundfield the player was exposed to or not?
I have since regulary observed that on my rather more sophisticated replay gear CD's that are fairly scratched sound rather "bad", hazy, as i some low level resolution is gone. I have aso found that these CD's can be rescued by ripping them to HD using EAC in paranoid mode (it tends to take a long time to rip) and then recording it on a new CD.
These are extreme cases and note that I did not posit the Vibration/Error Correction as THE EXPLANATION, but as a possible one.
Now, would consider that if the resonance behaviour of a CD player was changed and a CD with a large number of micro scratches (often invisible to the naked eye) was played that an audible effect MAY be possible, which is what I suggest, or do you feel that you can exclude the above suggested effect in the above suggested circumstances reliably to the point of saying "It cannot logically happen"?
Sayonara
This is from 'Digital Audio Technology' Dr. Doi: p144" ... Delta T is the jitter margin, and if jitter exeeding this value occurs, random errors will increase to the level that it becomes impossible for a machine to read the signal correctly. Of course, the reproduction waveform will, as a rule, deviate from the ideal and this in itself will reduce the jitter margin and lead to an increase in code errors. " This basically tells me that so long as the jitter is does not exceed a very large amount, it is unimportant. Is this true? How about other effects? This was all that was said by Dr. Doi of Sony in 1979. Check it out for yourself.
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