Digital Audio Myths - Listening on a PC

The extraction of audio involved the mechanic issue, isn'it? So read again what "What hifi" said:

"Our recent reviews of various CD-RW and MiniDisc recorders have attracted a flurry of correspondence, much of it via e-mail, denouncing the results we reported. 'How can different CD-RW discs/MiniDisc blanks/CD-RW recorders sound different?' they howl, adding, 'Surely the machine/disc combination either records the ones and zeroes or it doesn't. After all, different floppy discs don't make word-processor documents read better or worse, do they?'

It's hard not to argue with that last bit of logic, even if sometimes the reviewing staff on the magazine would love to be able to blame their floppies (!). But experience has taught us that, just as different CD players impose their own sound on a recording, so the various digital recorders on the market, and even the various brands and types of blank media available for them, can make a difference.

So what's going on? Digits are either there or not, right? The answer to that is 'kind of...' since all digital systems rely on error correction to get the sound from the disc to the analogue outputs in a recognisable form. The less hard the correction systems are having to work to reconstitute the original sound, the better the reproduction becomes.

What's being corrected is faults in the data, caused by anything from scratches on discs to mistracking of the laser pickup, from fluctuations in disc speed to wobbles in the spinning disc, and from low reflectivity causing misreading to vibrations caused by someone walking across the room. And that's before you get into electronic failings such as jitter...

Trouble is, a CD or MD player looks dead simple: you bung in a disc and it just plays music, just like these words are about to be saved to a hard disc on a computer and when we want to read them they'll come back on the screen exactly as they were typed. Hopefully.

But the fact of the matter is that CD players, and digital recorders, are all about high-precision engineering operating in a fairly hostile environment. For example, the laser pickup system in a CD player, or the write head in an optical or magneto-optical recorder, needs to move in three dimensions, alter its power and focus, and deal with a disc spinning at a constantly-changing speed, and do all that on a microscopic scale.

Thus anything that can make this task easier, be it discs with greater reflectivity, more even spirals of pits, or even a more consistent optical layer, is likely to give a better sound.

No, all digital equipment doesn't sound the same, however much logic might suggest otherwise - in fact, it's a miracle most of it is so consistent... "

WhatHiFiSound+Vision "

oliverstoned wrote: Why don't you admit that a 20 € drive can make little reading error-especially with vibes- which cause the correction circuits to work more, which result in harsh sound. That's the initial discussion, btw.

Because it's not true. Try it yourself or say no more, I'm tired of explaining.

Install CDex, rip some CDs while shaking the drive, using scratched CDs ... whatever. then compare the files, and if they differ, come back and complain. I'm certain that the ripped files will be identical bit by bit. That would not be possible if the drive was making errors, the resulting files would all be different then because of the shaking/vibes, which is completely different for each rip.

There ...

P R O V E N    W R O N G.

...withouit errors in the sense of a gap, but adding distorsion by missing a bit here and there, maybe.
And how do you explain the intervention of correction circuits?
Considering the software you are talking about, that would be an iinteresting exp, as long as there's no correction circuits involved.



Here's an illustration of a (standard)cd drive which will help our readers to understand the mechanic issue.

oliverstoned wrote: ..and i verify by myself another point is that some kind of blank cds sound different than others, thanks to the chemical product used for the reflective part of the CD. How do you explain that?

IMO that's esoteric bullcrap. Again: If you don't believe me, ask ANY computer expert whom you trust more than me.

You have heard of the word "placebo", haven't you?

BTW: You asked about the error correction:

http://en.wikipedia.org/wiki/Cyclic_redundancy_check

oliverstoned wrote: Yes i know what placebo is. It's like when someone wants to believe that what he has studied in a book fits with the facts.

I have proven my theory to be true, so it cannot be a placebo. Facts don't lie. I have said repeatedly that much of what you say is true, but the chemical substance of a CD doesn't affect the sound.

Let's approach this from another direction. When a CD is manufactured, what essentially happens is that a 650 MB file is transfered to a big machine which somehow prints that file onto a CD.

Now let us suppose that I can read that file from such a CD so that it matches the file which was sent to the CD pressing "machine" (I'm referring to that as a black box, I know it is more complex). Bit for bit identical.

If that is so, how can the material of the disc affect the sound? The material, the mechanics, the moon phase ... neither of that can retrieve more information from the disc than what was in the file which was used to create it.

cobb wrote: I'm sure oliverS is just doing this to wind you up Mike. What's he saying now- that the digital information on any two cd's (that contain the same information) from different manufacturing processes can produce different results. Huh? Any two cd's holding the same original information can only be identical in the binary code they represent.

Thanks cobb ... I'm not willing to give up yet.

BTW: I think he's talking about different CD-R media types, not pressed CDs. But of course what you (and I) said applies to them as well.

Edited by MikeEnRegalia

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Not all CDRs are created equalBy Ron Kubara, Business Development Manager, Noritsu Canada Ltd.Ron KubaraImage permanence for CDRs (Compact Disc Recordable) is an area that is not well known or understood by thegeneral consumer, nor by many photo labs. Contrary to popular belief, most CDRs are not permanent, and low-priced CDRs may not be readable at all and error in as little as two years.A cheap CDR is great for moving files fromone PC to another, but risky if being used toarchive files or images. Quality CDRs utilizehigh-quality recording and reflective layers,and are well sealed to reduce the harmfuleffects of the human environment.The material used for the plastic substrate (polycarbonate) of the CD and CDR is also important, as it needs to begas impermeable. Unfortunately, no plastic is; but some plastics are better than others. Even more important is thequality and thickness of the top coatings used to seal layers coated on the substrate.Prerecorded CDs are made by “stamping” the information into the plastic substrate, then analuminum alloy coating is applied to the “bumpy” stamped surface. The laser either reflects offthis reflective layer and a “1 bit” is determined, or the laser is deflected by the “stamped” bumpand a “0 bit” is determined. Contrary to popular belief, the recorded layer of a CD/CDR is not“sandwiched” within the plastic substrate. A clear lacquer protective layer is put on top of thealuminum reflective layer. A label is put on top, or a thick ink coating is applied. As the CD isread from the plastic side, a paper, plastic or ink label applied to the CD provides extraprotection against the data surfaces being scratched.CDRs are not stamped with the data; they are burned with data by the end user. The plastic polycarbonate,however, is stamped with splines (tracks or lines) for the laser to follow. A recording layer is also referred to as thedye layer, and it is sprayed on top of these splines. Four basic chemical formulae are used for the recording layerdye:1.Cyanine/light green/blue in color: low cost to make, most common and lowest permanence.2.Phthalocyanine/transparent with a slight green tint: highest permanence and second most common.3.Metallized Azo/blue: similar in quality to Phthalocyanine, costs less to make and are not common.4. Formazan/light green: combination of Cyanine and Phthalocyanine, similar in quality to Phthalocyanine, costsless to make, and are not as common.CDR manufacturers may modify one of these dyes and create a custom, proprietary formula and/or change thetraditional color of the dye. Thus, CDR color cannot accurately be used to determine the type of dye used.CD read lasers are infrared and are not affected by the color or visible light opacity of the dye. As a result, therecording layer dye color is irrelevant to the laser, as it will effortlessly pass through any dye that is not infraredopaque. The dye will become infrared opaque when burned by the write laser.“Funky” CDRs have a colored dye layer in front of the recording layer dye, creating colored CDRs. Black CDRsblock visible light from reaching the recording and reflective layer; thus, these layers cannot be seen by the eye.Yet, the type of black dye used will let the infrared laser pass.Gamers and music experts believe black CDRs produce better quality CDRs, but this researcher could not find anyscientific evidence to support this claim. As a black layer prevents visible light from reaching the recording layer dye(these dyes will fade over time when exposed to visible light), a black layer may increase longevity over an identicalgrade CDR when both are stored in the light.
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A reflective coating made of silver alloy, pure silver, or pure gold is layered on top of the recording layer. Althoughsilver will show the true color of the recording layer dye, gold will change the dye color because of its yellowishcolor. The burning laser melts a “pit” into the dye, which then blocks the read laser from reflecting back, and a “0bit” is determined. A good dye burns a nice clean pit, so the read laser knows for sure if it is a “0 bit” or “1 bit.” If theburn is not clean and the edge is not a clean cut, the CDR will produce an error.To protect the coatings, lacquer is applied, and high-quality manufacturers make it nice and thick or will even applya separate protective coating. Poor CDRs have very little protection on the coatings and will scratch easily, orworse, delaminate. By writing with a nonwater-base felt pen, the ink could make its way to the data layer anddamage a poorly sealed CDR. But be aware that even the best-coated CDRs can be damaged over time bynonwater-based felt markers.It is difficult to use CDR color only as a guide; but as a general guideline, if the CDR does not have a color tint, it islikely a lower-quality silver alloy with a poor dye layer. Blue, green, and faint green CDRs will be good if they usedquality silver. Unfortunately, there is no way to know for sure. Gold CDRs are the best because, when themanufacturers use gold, they use a quality dye. But don’t be fooled by manufacturers that place a gold-color labelon the non-read side, or the ones that add a funky gold-color layer on the read side.There are several reasons for good or poor CDR permanence.1. Plastic (polycarbonate substrate) is oxygen permeable. Oxygen eventually makes its way through the non-lacquered side (as well as the lacquered side in some cases) and reaches the reflective layer. As aluminumcorrodes when exposed to oxygen, and silver corrodes or tarnishes when exposed to sulfides in air, airreaching the reflective layers will cause corrosion, causing a read error. This could happen in as little as twoyears with poor CDs. Gold CDRs are best in this area, followed by gold/silver alloy. Silver/aluminum alloy is thepoorest.Equally important is the optical quality of the plastic. High optical-quality CDRs permit the light to pass throughthe polycarbonate with little or no diffusion, permitting a cleaner burn to the dye. The spiral grooves stamped tothe CDR vary by manufacturer. It is easier and cheaper to make a V-shaped groove than a sharp edge Ugroove. A V-type stamp will have a higher degree of skipping errors, as the laser may not be able to trackproperly, much like the needle of a phonograph if it does not have enough weight on it. Additionally, the stampwill wear as it stamps CDR after CDR, resulting in a U-shaped groove becoming more V-shaped over time,which may lead to skipping and errors.2. The dyes used in the recording layer are light sensitive, and will react to ambient light and fade over time.Quality CDRs use a dye that resists fading. To be safe, store them in the dark.3. Humidity may seep through a poor lacquer coating. Quality CDRs are well sealed and resist seepage frommarkers and moisture. To make them last, store in low humidity, and use water-based markers and write on thecenter core.4. A scratch on the base side can be repaired, but a scratch on the lacquer side makes the CD a coffee tablecoaster. Quality CDRs have a thick, protective coating to resist scratches.Archiving reports vary by manufacturer, but 70 years would be low for a quality CDR, with the norm being 100years. Some manufacturers of gold CDRs claim 100 to 200 years. You generally get what you pay for. Don’t putthose precious images on a CDR that costs just a few nickels and dimes.The opinions expressed in this column are not necessarily those of Photo Marketing magazine or Photo MarketingAssociation International.

Another point: i've noticed on my audiophile burnerthan 2X speed degrades much, compare to normal speed...

goose wrote: oliverstoned wrote: ..and i verify by myself another point is that some kind of blank cds sound different than others, thanks to the chemical product used for the reflective part of the CD. How do you explain that? You argue that analogue is better than digital because digital is just 1s and 0s. If digital is just 1s and 0s, then the chemical has no bearing. If the chemical used alters the sound, there must therefore be more to digital recordings than just 1s and 0s, and so why is analogue better?

Could you please reformulate?