How CD and DVD Players work

[Deleted]

www.optics.arizona.edu/ODSCsponsors/03-01-31-417-Semi-AnnualReport/D%20-%20Mansuripur.pdf

See also :
www.iar-80.com/page53.html - Improving CD Sound. p.53-59
Also check out the other Home Page articles at the concluding link.

I have previously read some of the earlier articles in IAR that were referred to, but I am unable to access them at the present time.
Alex

The quote below is from the conclusions of the "Improving CD Sound" article.

"Adding It All Up

If we add up everything we've learned in the four lessons above, it suddenly becomes clear that all kinds of CD tweaks can and indeed should be effective in making a sonic difference. Those who deride CD tweaks as snake oil are actually themselves the peddlers of improbability, or perhaps they naively subscribe to the popular misbelief that bits is bits, that digital is robust if not immune to external influences, and therefore nothing can possibly make any sonic difference. Now we know better. Digital is vulnerable, fragile, and as susceptible to analog external influences as analog ever was. Digital is as fertile a ground for inventive tweaking as the vinyl LP ever was, and legitimately so."

[rowuk]

How a cd player works: insert disc, push start.

Calling the sceptical names does not legitimize the tweakers cause. Digital is no where near as fragile as analog was and never will be!

With a bit of common sense very good and REPEATABLE playback can be achieved with very little effort. Even the very discerning audiophile can get an AMAZING amount of believable sonics with a couple of mouseclicks and modest modifications to the playback equipment.

If the reviewers would listen to more real music, they would learn that their audio experience has little in common with the original. Most "audiophiles" that I know are disappointed at the piss poor imaging at an orchestra concert, the lack of black and slam, incredible amounts of phase distortion created by contrabasses spaced 8 feet apart or the clicking of real saxophone keys. They are often VERY surprised at the amount of energy coming off of the ceiling of the concert hall (a violins sound is pointed UP) as well as the directionality of a trumpet. One of the most difficult concepts for those that can hear the grass grow is the HUMAN touch that does not have a studios perfect rhythm or pitch.

What I learned from the article is that some avid tweakers throw around terms that they do not understand, often need miracles instead of common sense truth and use the same bad manners as in the analog days to criticize those who do not soak up all of the snake oil that they dish out. If they would search for truth, they would discover that less is more and that simple physics, biology and chemistry deliver more audible pleasure than all of the flavor of the week wonders. Why can't some admit that something sounds better for some reason that they don't understand? A SSD can sound better than a harddrive. I can't explain it and have read NOTHING with a compelling argument. So What? Just accept that it is better if it sounds that way. I tried it and liked it.

The only statement that I unequivocally agree with is "Digital is as fertile a ground for inventive tweaking as the vinyl LP ever was, and legitimately so." Making money is indeed legitimate.

We should be thankful for Rock Grotto. Here we have serious listeners that do not need big wallets for big sound. We are still working on the miracles part.................

[Deleted]

The only statement that I unequivocally agree with is "Digital is as fertile a ground for inventive tweaking as the vinyl LP ever was, and legitimately so." Making money is indeed legitimate.

Robin
Despite the claims made elsewhere, the Demag and Ion treatment appeared to have a negative effect. Perhaps Geoff in NYC should have rubbed the CD numerous times on his acrylic jumper before comparing before and after ? Even then ... Some claims do make you wonder, but I have read quite a few good reports about the machine that corrects the CD circumference, and gives it a chamfered edge .
Perhaps some enterprising salesman could start a mini franchise operation in Bridgestone Tyres outlets, where they could balance your CDs for you ?

Alex

[rowuk]

Jan 5, 2010 21:58:45 GMT @sandyk said:

The only statement that I unequivocally agree with is "Digital is as fertile a ground for inventive tweaking as the vinyl LP ever was, and legitimately so." Making money is indeed legitimate.

Robin
Despite the claims made elsewhere, the Demag and Ion treatment appeared to have a negative effect. Perhaps Geoff in NYC should have rubbed the CD numerous times on his acrylic jumper before comparing before and after ? Even then ... Some claims do make you wonder, but I have read quite a few good reports about the machine that corrects the CD circumference, and gives it a chamfered edge .
Perhaps some enterprising salesman could start a mini franchise operation in Bridgestone Tyres outlets, where they could balance your CDs for you ?

Alex

I would prefer to put the CD on a flatbed scanner to "read" it without it needing to turn and then with OPR (optical pit recognition) turn the scan into audio. That would jitter the hell out of the snake oil vendors!

It may be cheaper to get some enterprising young programmer to slow a CD drive down to a crawl and read it at 1/4 or better 1/10th speed, pit for pit, bit perfect, jitter free.

I think there is an audiophile advantage going to the Hubble mirror and lens dealer to get your CDs polished to optical perfection with no diffraction and then antistatically treated.

The problem is, if we get the information off the disk perfectly, there will still be something for the snake oilers...............

[Deleted]

I have a VERY THICK book (a factory coarse I followed on CD players as a reapairman) on how the CD works.

The tracking of the pits is a complex task performed by a separate circuit that drives the lens coils and it's ability to do so greatly varies per manufacturer and the state the optical/electrical circuit is in (adjustments/aging/dirt)

There is no magic involved in the recovery of the EFM bit pattern on the disk that in a later stage will be fed to a X'tal clocked DAQ with it's own physical properties that DO matter.
Every bit in the Eight to Fourteen Modulation signal on the disk will be used to calculate what the recorded bits are supposed to be. (within a certain limit of time in loss/deterioration of this signal and depending on the kind and place in the datastream .

The databits in the EFM datastream also are not in a single row behind each other but scattered in a certain order to achieve the best posible results when data is missing and by the use of more than enough redundancy can be calculated back to its original values without any problems.

The pits on the CD are most certainly not read and fed directly to a DAC.. a LOT of number crunching and processing is between this process.

I once made a visual output (LED) on the 'uncorrectable error' output pin of the processing IC which sometimes lights up and still can't be heard.
Only longer errors (damaged CD's) can deteriorate the sound.
a digital 1 to 1 copy is still a copy and I (nor anybody I know of) is able to hear differences.

If it does.. someone explain to me WHAT 'extra' signal (that is not made of 1's and 0's) will be responsible for it ?

But this is only about the technical stuff.
I don't want to strain myself searching for something nobody knows WHAT to look for and can be seen as subjective as it can't be explained but only be 'reasoned' or guessed at with the most beautiful theories and questionable solutions.

I know ... some people will hate me for this conviction and consider me NOT to be a true audiphile.
They are right.. I am not.. I am just a very skeptical but 'realistic' audiofool.. who prefers to listen to music and enjoy it instead of being annoyed and looking for things they can't be SURE of they really EXIST all the time.

(Now I have done it !)

[Deleted]

If it does.. someone explain to me WHAT 'extra' signal (that is not made of 1's and 0's) will be responsible for it ?

Frans
Has anybody claimed there is an extra signal ?
Don't be so quick to dismiss timing errors, due to noise and vibration, PSU inadequacies etc.which are commonly referred to as Jitter, although that would not be strictly correct terminology.
Without subjective observations, there would not be the need for objective measurements.
Alex

[andy]

I think i prefer Fran's title of audiofool than audiophile.....

I am an Audiofool!

[robertkd]

Umm actually an object rotating/spinning in a magnetic field is more likely to be demagnetised and a n object in a static (stationary) field is more likely to be magnetised just a thought,..

As for digital systems being "fragile" you have to consider the terabytes nah petabytes traversing the WWW with nearly zero error, scale that back to a CD and their dreaming.

no fertile ground for scamming more like it,..

[robertkd]

@fran

you left out NZRI and Cross-Interleaved Reed-Solomon Coding

Here's a nice animation for the optics

micro.magnet.fsu.edu/electromag/java/cd/index.html

[Deleted]

a digital 1 to 1 copy is still a copy and I (nor anybody I know of) is able to hear differences.

-- Multiple Instances of One CD

The focus of this article is on ways you can improve the sound from each single CD in your collection, so the examples just above, showing evidence that eye pattern quality affects sound, pertain to changes in the sound of a single CD. But perhaps the strongest evidence, that eye pattern quality does affect sound, comes not from comparing the sound of a single CD before and after, but rather from comparing the sound of multiple, alternative CD copies of what should be the same "digital" data and therefore should presumably sound identical. The fascinating finding is that they in fact don't sound identical, and in many cases the only possible (or most plausible) cause is a difference in the quality of the eye pattern.
Our first example of this sort pertains to multiple instances of exactly the same CD. As we discussed in IAR issue 79, we compared two instances of a first edition classical CD from a major label, and they sounded very different in sonic quality. What could explain these sonic differences? CDs are plastic discs, pressed in hot molding machines, just as vinyl LPs are. The pits and pit edges that will create the analog eye pattern are mechanically molded or stamped into the plastic by a stamper mold. Since the title was a small run classical CD, the mother for any plural CD stampers was presumably the same. But stampers wear over time, as they press out hundreds of plastic CDs. The stamper that pressed out one instance of our classical CD could have been more worn than the other, or perhaps both instances of our CD title came from the same stamper, but one instance came from later in the life of that stamper, so it was more worn. A more stamper could well stamp out pits with edges that are more gradual, more sloppy, less sharply and cleanly defined. Alternatively, the thin flash of aluminum that does the reflecting might have been better quality or better applied on one CD instance than on the other. Or perhaps the polycarbonate substrate (body) in one CD instance was from the bottom of the plastic material barrel, so it did not transmit reflected light as well. Or, although both CDs were brand new, perhaps one had a thicker coating of mold release compound than the other, and thus did not reflect as strongly.
In any case, the two CD instances had to be physically different in some way, since they sounded different. We just noted three possible physical differences above: poorer (less sharply defined) pit edges due to a worn stamper, poorer reflectivity due to inferior aluminum coating, and/or poorer reflectivity due to contaminated disc surface. Note that all these possibilities affect the quality of the analog eye pattern. So, whichever of these possibilities is the actual cause, they all support the same finding that's at issue here: the quality of the eye pattern does indeed affect the final sonic quality you hear.
The popular misbelief is that multiple instances of the same CD should sound identical, because CDs contain digital data, and these multiple instances of the same CD contain identical digital data, and bits is bits, so they must sound the same. But now we know that the data are read from a CD in analog form, not digital form. And we know that analog factors like sharpness of molded pit edges and degree of reflectivity affect the quality of the analog waveform that is read from the CD. So in point of fact a CD contains analog information (including sharpness of pit edges and degree of reflectivity), not digital information. True, that analog information indirectly represents the amplitudes of music signal samples in digital format. But that analog information is still a very concrete, real intermediary between the abstract digital representation of music on the disc and the later digital interpretation and recreation of that digital information inside your CD player, which then subsequently re-converts its freshly created digital data back to analog.
In a very real sense, the music signal, only abstractly represented as digital on the CD, goes through a digital-to-analog conversion as the concrete information is actually read off the CD, then an analog-to-digital conversion within your CD player, as your player interprets the incoming analog information to freshly create a digital bit stream, and then later another digital-to-analog conversion in your CD player's DAC chip, so that your CD player can output an analog music signal to your amplifier. Now, we know that each conversion of a signal, digital-to-analog or vice versa, brings with it the potential for degradation of the music, since each physically real conversion is less than perfect; so the mere fact that we now realize there are two more conversions than popular misbelief supposes is bad news, suggesting that laser media are less perfect than previously thought.
But the real kicker here is that, thanks to this extra, heretofore unsuspected double conversion, your music signal is actually in analog form for an intermediate stage in the process. And analog signals are notoriously susceptible to being degraded by external analog influences. So, while your music is in analog form at this intermediate stage, its sonic quality is vulnerable to external analog variables, variables like degree of pit edge sharpness and degree of disc reflectivity, both of which affect the analog degree of quality of the analog eye pattern waveform actually read off the disc.
Of course, the whole reason for going to a purportedly digital medium like CD, instead of an analog medium like vinyl LP, was because digital is supposedly robust and immune from external influences. But, by converting your music to analog at this intermediate stage in the chain, laser media like CD actually can make your music vulnerable to those same analog corruptions and variables we experienced with analog vinyl LP. One wonders what the design engineers were thinking (or if they were thinking), when they designed a new digital system to have similar analog vulnerability as a purely analog system. Hello? Is anybody in there?
We all fondly remember how, in the old days, we'd compare two pressings of the same analog vinyl LP, and find they sounded different because one came from a more worn out stamper, or one had more mold release gunk, or was made from inferior reprocessed material (vinyl vs. now polycarbonate or reflective aluminum) instead of virgin materials. So it is bitterly nostalgic to find that CDs are just as vulnerable to these same analog influences, thanks to the extra conversions which make the signal analog for a while.


www.iar-80.com/page57.html

[robertkd]

rowuk

And how dare those wind instrument players sneak a breath in between bars I mean it just isn't hi fi,....

[Deleted]

As for digital systems being "fragile" you have to consider the terabytes nah petabytes traversing the WWW with nearly zero error, scale that back to a CD and their dreaming.

Don't places like Rockhampton have DTV ?

[robertkd]

Feb 2, 2010 10:08:05 GMT @sandyk said:

a digital 1 to 1 copy is still a copy and I (nor anybody I know of) is able to hear differences.

-- Multiple Instances of One CD

The focus of this article is on ways you can improve the sound from each single CD in your collection, so the examples just above, showing evidence that eye pattern quality affects sound, pertain to changes in the sound of a single CD. But perhaps the strongest evidence, that eye pattern quality does affect sound, comes not from comparing the sound of a single CD before and after, but rather from comparing the sound of multiple, alternative CD copies of what should be the same "digital" data and therefore should presumably sound identical. The fascinating finding is that they in fact don't sound identical, and in many cases the only possible (or most plausible) cause is a difference in the quality of the eye pattern.
Our first example of this sort pertains to multiple instances of exactly the same CD. As we discussed in IAR issue 79, we compared two instances of a first edition classical CD from a major label, and they sounded very different in sonic quality. What could explain these sonic differences? CDs are plastic discs, pressed in hot molding machines, just as vinyl LPs are. The pits and pit edges that will create the analog eye pattern are mechanically molded or stamped into the plastic by a stamper mold. Since the title was a small run classical CD, the mother for any plural CD stampers was presumably the same. But stampers wear over time, as they press out hundreds of plastic CDs. The stamper that pressed out one instance of our classical CD could have been more worn than the other, or perhaps both instances of our CD title came from the same stamper, but one instance came from later in the life of that stamper, so it was more worn. A more stamper could well stamp out pits with edges that are more gradual, more sloppy, less sharply and cleanly defined. Alternatively, the thin flash of aluminum that does the reflecting might have been better quality or better applied on one CD instance than on the other. Or perhaps the polycarbonate substrate (body) in one CD instance was from the bottom of the plastic material barrel, so it did not transmit reflected light as well. Or, although both CDs were brand new, perhaps one had a thicker coating of mold release compound than the other, and thus did not reflect as strongly.
In any case, the two CD instances had to be physically different in some way, since they sounded different. We just noted three possible physical differences above: poorer (less sharply defined) pit edges due to a worn stamper, poorer reflectivity due to inferior aluminum coating, and/or poorer reflectivity due to contaminated disc surface. Note that all these possibilities affect the quality of the analog eye pattern. So, whichever of these possibilities is the actual cause, they all support the same finding that's at issue here: the quality of the eye pattern does indeed affect the final sonic quality you hear.
The popular misbelief is that multiple instances of the same CD should sound identical, because CDs contain digital data, and these multiple instances of the same CD contain identical digital data, and bits is bits, so they must sound the same. But now we know that the data are read from a CD in analog form, not digital form. And we know that analog factors like sharpness of molded pit edges and degree of reflectivity affect the quality of the analog waveform that is read from the CD. So in point of fact a CD contains analog information (including sharpness of pit edges and degree of reflectivity), not digital information. True, that analog information indirectly represents the amplitudes of music signal samples in digital format. But that analog information is still a very concrete, real intermediary between the abstract digital representation of music on the disc and the later digital interpretation and recreation of that digital information inside your CD player, which then subsequently re-converts its freshly created digital data back to analog.
In a very real sense, the music signal, only abstractly represented as digital on the CD, goes through a digital-to-analog conversion as the concrete information is actually read off the CD, then an analog-to-digital conversion within your CD player, as your player interprets the incoming analog information to freshly create a digital bit stream, and then later another digital-to-analog conversion in your CD player's DAC chip, so that your CD player can output an analog music signal to your amplifier. Now, we know that each conversion of a signal, digital-to-analog or vice versa, brings with it the potential for degradation of the music, since each physically real conversion is less than perfect; so the mere fact that we now realize there are two more conversions than popular misbelief supposes is bad news, suggesting that laser media are less perfect than previously thought.
But the real kicker here is that, thanks to this extra, heretofore unsuspected double conversion, your music signal is actually in analog form for an intermediate stage in the process. And analog signals are notoriously susceptible to being degraded by external analog influences. So, while your music is in analog form at this intermediate stage, its sonic quality is vulnerable to external analog variables, variables like degree of pit edge sharpness and degree of disc reflectivity, both of which affect the analog degree of quality of the analog eye pattern waveform actually read off the disc.
Of course, the whole reason for going to a purportedly digital medium like CD, instead of an analog medium like vinyl LP, was because digital is supposedly robust and immune from external influences. But, by converting your music to analog at this intermediate stage in the chain, laser media like CD actually can make your music vulnerable to those same analog corruptions and variables we experienced with analog vinyl LP. One wonders what the design engineers were thinking (or if they were thinking), when they designed a new digital system to have similar analog vulnerability as a purely analog system. Hello? Is anybody in there?
We all fondly remember how, in the old days, we'd compare two pressings of the same analog vinyl LP, and find they sounded different because one came from a more worn out stamper, or one had more mold release gunk, or was made from inferior reprocessed material (vinyl vs. now polycarbonate or reflective aluminum) instead of virgin materials. So it is bitterly nostalgic to find that CDs are just as vulnerable to these same analog influences, thanks to the extra conversions which make the signal analog for a while.


www.iar-80.com/page57.html

what do they mean the data is read from a CD in analogue form ?

[Deleted]

what do they mean the data is read from a CD in analogue form ?

You could try reading the rest of the story at the link given .

Not that I am saying all of it is necessarily correct, as there still appears to be a lot of conjecture about the subject from most sources.
Let's face it, if Sony and Philips had got it all working as well as they claimed originally , then there wouldn't be so many people still playing and enjoying Vinyl recordings !

[robertkd]

Well I tried that, but they seem to talk a lot of shit with not a lot of science to back up their shit, oh sure they use a lot of emotive descriptive words but not a lot of real tangible evidence,..

As for get it right well not really a lot of people still watch I dream of Genie, don't they,.. it doesn't mean it was good or better they just like it.

[Deleted]

Well I tried that, but they seem to talk a lot of shit with not a lot of science to back up their shit, oh sure they use a lot of emotive descriptive words but not a lot of real tangible evidence,..

Just as most qualified Engineers are unable to disprove what they are claiming ?
THe sad truth is that there does not appear to have been enough definitive published research in this area. It could also be that much of the research is regarded as commercially sensitive information, and not released.

[robertkd]

Feb 2, 2010 10:42:39 GMT @sandyk said:

Well I tried that, but they seem to talk a lot of shit with not a lot of science to back up their shit, oh sure they use a lot of emotive descriptive words but not a lot of real tangible evidence,..

Just as most qualified Engineers are unable to disprove what they are claiming ?
THe sad truth is that there does not appear to have been enough definitive published research in this area. It could also be that much of the research is regarded as commercially sensitive information, and not released.

Or that real advances are made with definable measurable repeatable attributes and not unmeasurable non-repeatable non-quantitative emotional assessments

PS As research has shown it would definitely be not released as it would be commercially sensitive to anyone claiming "magic"

[Deleted]

Or that real advances are made with definable measurable repeatable attributes and not unmeasurable non-repeatable non-quantitative emotional assessments

You guys still can't even explain why amplifiers with very similar specifications can sound so different !
Yes, I know, if the measured specifications are the same, they MUST sound the same.

W.A.L.O.C. !!!

[robertkd]

Feb 2, 2010 11:48:37 GMT @sandyk said:

Or that real advances are made with definable measurable repeatable attributes and not unmeasurable non-repeatable non-quantitative emotional assessments

You guys still can't even explain why amplifiers with very similar specifications can sound so different !
Yes, I know, if the measured specifications are the same, they MUST sound the same.

W.A.L.O.C. !!!

well this is for starters,...

[Deleted]

I happen to be a qualified engineer and HAVE disproved what 'THEY' are saying on numerous occasions. ;D
There are LOTS of scientific books written about EXCACTLY what and how the CD format is all about.
NOTHING is not known about it.
That's why they call it Logic !
0110111011 = 0110111011 and NOT 0110111011+"magic"
During subjective tests the "magic" cannot be proven to "skeptics" like me that it is there (they have not been able to, yet ...) as well as "NON skeptics i.e. "believers" cannot be convinced the magic isn't there and it is probably ...

There is little point in debating this issue really as 'believers' are not going to be convinced to believe otherwise as well as "Skeptics" (mostly engineers who have (deep ?) knowledge of electronics) cannot be convinced that besides common sense and repeatable/measurable/prove-able evidence the "Magic" also plays an, yet unchartered, role in the equasions.

Only a few handfull qualified technicians aside perhaps