Theoretical question about how CD's work

Maybe Michael Green is right, after all. I.e., Lightweight systems sound better than heavy systems. The sampling rates are much higher for Blu Ray. Large capacitors and transformers in older, heavier CD players would not be good for the sound. So, it’s a little like comparing apples to oranges. I find small, lightweight (portable) CD players have inherently good sound. One assumes Blu Ray discs are subject to scattered light and vibration issues just like CD players. 

Maybe the high speed and narrower laser beam is at the heart of why a cheap Sony Blu-ray player sounds so great compared to 80's and 90's CD players.  I had huge and very heavy Sony CD players that sound thin compared to a one pound Blu-ray player.  This suggests that the transport quality maybe better now than then as well as the DAC formulation.

Have you flipper your gizzard? Nobody said CDs are like Laserdiscs. I already explained why laser reading is an analog process. That doesn’t mean the transitions from pits to lands and lands to pits don’t represent 1s and 0s. But those 1s and 0s represented by the transitions do not (rpt not) represent the music signal (waveform).

The laser reading of the transitions is an analog process. The laser reads, ON, OFF, ON, OFF according to whether the photodetector receives a reflected signal or no signal. The transitions occur between ONs and OFFs. And the system keeps track of the time periods between transitions. So, the lengths of pits and lands is also important in organizing the transitions into meaningful data strings, according to the Redbook standard.

The “1s and 0s” detected by the photodetector have to be decoded into predetermined strings of meaningful data downstream. As the link I provided a couple weeks ago shows there are approximately 9 or so discreet strings of data that are read off the Compact Disc. The 1s and 0s represented by transitions don’t mean anything until they’re organized even when they’re organized they still don’t mean anything until they go through a Digital to Analog Converter DAC. But, unfortunately, as I’ve stated many times, by the time the organized 1s and 0s get to the DAC it’s too late to recover from all the damage to the original data on the CD. The reasons for the damage include,

1. Scattered laser light that above a certain energy level gets into the photodetector and is interpreted as real signal. Since the laser is invisible infrared 780 nm attempts to block scattered light with green pens is only fractionally successful. There is a red component to the CD laser for safety reasons. It’s that red component of the scattered light that green pens absorb.

2. Mistracking of the laser caused by external vibration as well as vibration of the Compact Disc itself while spinning. The fluttering and wobbling is caused by out of round discs and exacerbated by the non level spinning of the disc. Mistracking occurs even though Reed Solomon Error detection/correction codes supposedly correct all errors and even though the laser tracking servo system supposedly keeps the laser on the data spiral at all times.

OK so I learned something. Analog means distance and speed dependent. I am off this thread . . .

There are quite a few reasons why the same issue CD of a recording from different CD manufacturing plants sound different on the same CD player.

The accuracy of the process of laying down the bits and lands on the metal master.

The accuracy of producing the actual CDs from the metal master. The edges/transitions between pits and lands must be perfectly clean and correct with respect to timing (lengths of pits and lengths of lands).

Differences in the inks used for the CD label. Some inks may be more ferrous. Also if the colors of the inks are different that would influence the sound, too.

The thickness of the CD can influence the sound since a thicker CD will be stiffer and not flutter as much during play as a thinner one.

The transparency/purity of the polycarbonate layer. The nominal transparency of polycarbonate is actually only about 91%. SHM-CDs employ a more transparent material for the clear layer. Hence Super High-performance Material (SHM). Less transparency, more laser light scattering.

The purity and composition of the metal layer. Some metals and alloys have higher reflectivity for infrared light than others.

The variation in roundness of the CD. We know that out-of-round CDs flutter and flop around more than CDs that are perfectly round, causing mis-tracking.

Someone who actually knows what they're talking about, ie NOT kosst_amojan :

Bits is bits? 
Although CD manufacturing appears to be a straightforward process of stamping inviolate ones and zeros into a plastic disc, these manufacturing techniques introduce analog-like variations in the quality of the HF signal read from the disc. 

Because the HF signal recovered from the finished CD is created by the tiny pit-and-land structures, it follows that any changes in pit shape will affect the HF signal. Well-formed pits produce a good-looking HF signal; poor pit geometry creates a poor-quality HF signal. 

A clean HF signal is essential not only to low error rates and good tracking ability, but also to sound quality. Although the HF signal undergoes significant processing before the raw audio data and timing clock are recovered, many digital designers agree that the HF signal's shape and quality affect how the disc sounds. Some high-end transports even have circuits to clean up the HF signal before it's sent to the decoding electronics. 

That the HF signal's quality affects the sound is suggested by many examples of audible differences where there should be none. In 1986, Doug Sax (footnote 4) first alerted me that CDs made from the same CD master tape, but pressed in different factories, sound different. Doug routinely buys CDs of records he's mastered and compares them to the original CD master tape from which the CD was made. He has found a huge variability in sound quality between different pressing plants—some plants produce discs that sound very similar to the original; others make discs that sound dreadful. The only difference is in the manufacturing process. Indeed, engineer Bob Katz's experience, described in the companion piece to this article, further suggests that, although the binary 1s and 0s on two CDs may be the same, it doesn't necessarily follow that the discs will sound the same.

So its Doug Sax, who we're pretty sure can hear a difference, vs kosst_amojan, who we aren't sure can hear at all. This by the way is from the Stereophile article, The Analog Compact Disc. The key word in case you missed it kosst is analog, not digital, and it ain't no typo. It would seem you are once again way, way, WAY off base. https://www.stereophile.com/content/analog-compact-disc-page-2

Here’s some really bad news, especially if you purchase CDs from eBay. For anyone concerned about dynamic range on your CDs, you will find generally that CDs listed for sale are the compressed reissues. Usually, not always, the original CDs that came out in the 80s or 90s are the most uncompressed versions. This is a generalization, and I’m referring to classic rock CDs here. When an original CD of a particular album does come up for sale, especially if it’s a Japanese or German import, the price is double or triple.The trend is not your friend. Apparently everybody and his brother are dumping crappy overly compressed CDs. Which in a weird way is refreshing, inasmuch as your humble scribe is not the only person who eschews compressed CDs. 

Actually, I don’t think he did know that. As my old boss at NASA, Chuck Rounds, used to say, hit a man when he’s down. 

kosst_amojan

That's the stupidest thing I ever heard. Cheap, flimsy optical drives jammed into laptops have no problem tracking a CD spinning it more than 50 times normal play back speed.

Don't be silly. There's a big difference between playing CD audio  in real time and pulling data off a CD on a computer. I'm pretty sure you knew that.

Exhibit A

I recently heard a friend’s (big) system that employs a clamp down device on the CD. I was able to improve the sound considerably by using my Mystery Tweak 🤫 on the CD, which stiffens and damps the CD. This, gentle readers, means the CD clamp down device is not (rpt not) effective in preventing CD vibration and flutter. Even CD Rings ⭕️ which are a good idea and address the problem I’m referring to, are not completely effective, even though they add mass to the circumference of the disc, helping reduce flutter and wobble.

I just moved and set-up one of my video rooms. Yes, the IC to the receiver was high end as is the speaker wire (left overs from prior audio systems). Using an HDMI cable from an $85 blu-ray player, my CDs sound fantastic (in terms of tonality, dynamics, PRAT and imaging) using a Yamaha CR620 receiver and ADS 620 speakers. Also, 4 SR HFTs on the TV and front glass stand.  No, it doesn’t have the ambiance retrieval or bass slam (but goes down to probably 40Hz). I can’t believe how good it sounds (the room is also 18’ vaulted ceiling and about 48’ wide X 30’ deep). Even my wife commented on how good music sounds on it (it will take me some time to set up my audio rooms and I've just moved about 27,000 LPs/78s and 7,000 CDs-I never want to do that again).  So, a cheap ass blu-ray player can sound amazing. I have a collection of about 30 CD players like Denon, Sony, HK, Sharp, etc. from the 1980s and 1990s because I was so dissatisfied with the sound back then. Now, even a cheap player can sound miles better.  I might as well donate them and take the write-off.  Only a post 2000 DAC or high end CD player sounds better.

That is why a few CD manufacturers have created clamping/isolation devices for the CD wherein the vibrations from an out of round CD are greatly or completely diminished.  Even my EAR Acute has a flimsy CD tray and internal puck to hold it while it spins.  This is a basically a design error by most manufacturers in eliminating non-concentric and floppy discs.  Same with DVDs, Blu-Rays.

kosst_amojan
Folks, I don’t think anything more needs to be said after Geoff’s last post. How can you possibly top that list of ridiculous snake oil solutions to problems nobody has ever had?

And who cares how round the edge of the CD is? That doesn’t fix track concentricity issues. CD don’t spin on their outer edge. They spin from that hole in the middle. DUH. R

>>>>>The reason out of round CDs are bad for the sound is because they wobble and flutter during play due to their mass not being uniformly distributed. Thus, the laser servo mechanism is overloaded trying to keep the laser on the nanoscale track.

Here are a few other audiophile thingamabobs that improve the sound of CDs that ought to get the 1s and 0s crowd’s blood boiling 🥵.

Nespa High intensity strobe light CD treatment

The Intelligent Chip quantum Chip for treating CDs, and the Intelligent Box (Think Inside the Box)

Audio Deske CD Improver - edge beveler for making CDs perfectly round

The PWB Violet Pen for coloring the outer edge of the CD. Interestingly, the Violet Pen also works on LPs.

tomcy6
geoffkait

You may think of it as a logic puzzle.

In that case, logic tells me that you are trying to take advantage of highly suggestible people. 

>>>>You must be channeling Juror #3 from 12 Angry Men. “You can’t prove it!!” 😡

kosst_amojan
@geoffkait

"Since everything is known and can be found in Wikipedia or some online textbook we can dismiss any inconvenient arguments as not worthy of examination. Bravo, moopman!"

You don’t have any arguments worthy of examination. Pretty much everything is known about the function of the electromagnetic force so if it’s not in a reputable book, it’s nonsense. Anyone who buys into your hocus-pocus is simply gullible.

>>>>Koost, no need to go full retard on me. you should have listened to your mommy when she told you to stay in school. You don’t even know the difference between an electromagnetic wave and a force. 😬

Yes. But he has to be one badass monkey.

 You may think of it as a logic puzzle.

In that case,  logic tells me that you are trying to take advantage of highly suggestible people.

With today's online catalogs of tracks to download, especially in high res, why would anybody still want to buy a CD? It beats me why CDs do not encode regular wav or flac files, with much more effective error correction for buffered playback. Add a state of the art reclocker after that to get jitter down to lowest possible level and a DAC to suit your taste in terms of filtering and conversion, and you are good to go! Once the CD is properly ripped it is of no big use. 

tomcy6
Geoff, I’ve noticed that you have frequently posted about the scattered light problem since you started selling a product to help eliminate this problem. There’s nothing wrong with that if you discovered a problem and came up with a solution.

>>>>That’s might generous of you.

It would be helpful to us and you, though, if you provided the evidence that shows that scattered light increases reading errors for cds that cd players don’t correct. If the evidence is simply that you hear a subjective improvement when playing cds treated with your product, it would be good to know that too.

>>>>I’m afraid you’ll have to take my word for it. I’ll leave all the measuring to someone else. I’ll even leave the subjective opinion to someone else. You may think of it as a logic puzzle.

fleschler
geoffkait: generic, thin, bass shy, brittle, honky, synthetic, congealed sound. That maybe your definition of CD reproduction, but it isn’t mine or half a dozen close friends of mine. While we all appreciate the sound of a good LP, the average classical and jazz CD well mastered is stunningly good. I have 35,000 LPs and 7,000 CDs. I wouldn’t give up any of them because of their format limitations. I have near SOTA front ends which permit me to extract superior performance from each format. Even my 78s sound more alive, dynamic and tonally rich compared to most audiophiles systems.

>>>>Fabulous! 😛

One wonders why the Labs 47 Shigaraki CD player doesn’t advertise the advantage wrt scattered light, compared to closed designs. I imagine some stray light scattered off the pits will get into the detector but less than closed transports, I.e., everything else. Reading one review of the Labs 47 Shigaraki CD Player I gather they have not solved the scattered light problem based on the reviewer’s description of the sound.

Yes, I experimented with 40 or 50 CD players prior to 2006, trying to find one that approximated LP playback.  I hated CD reproduction until the 2000s.  The players got better as did the DACs.

Geoffkait   generic, thin, bass shy, brittle, honky, synthetic, congealed sound.  That maybe your definition of CD reproduction, but it isn't mine or half a dozen close friends of mine.  While we all appreciate the sound of a good LP, the average classical and jazz CD well mastered is stunningly good.  I have 35,000 LPs and 7,000 CDs.  I wouldn't give up any of them because of their format limitations.  I have near SOTA front ends which permit me to extract superior performance from each format.  Even my 78s sound more alive, dynamic and tonally rich compared to most audiophiles systems.  My most treasured vocal recordings are Ward Marston mastered to CDs.  There is no equivalent except buying $1 millions of "78"s, finding the correct speed, stylus size and equalization to play each.  No chance in my life of doing what Ward does.

Q asked by OP | <------------------------------------------------->|  This thread

The light travels really fast and it all arrives at the sensor at the same time so there is no problem except that Geoff needs to sell stuff.

Geoff, I've noticed that you have frequently posted about the scattered light problem since you started selling a product to help eliminate this problem.  There's nothing wrong with that if you discovered a problem and came up with a solution. 

It would be helpful to us and you, though, if you provided the evidence that shows that scattered light increases reading errors for cds that cd players don't correct.  If the evidence is simply that you hear a subjective improvement when playing cds treated with your product, it would be good to know that too.   

Geoffkait- I have a CD transport the "47 labs shigaraki" the CD sits on top of the player out in the open, do you think this helps with the scattered light problem?


Thanks, TISH

Apparently mapman’s butt is still stinging from something I said. Get well soon, Moops.

Geoffkait actually you are clearly the skeptic here. Don’t be such a sad sack! Why don’t you write a book and enlighten the world further then smart guy? I’m sure there are enough neurotics out there you can appeal to to make it a big seller and help your business.

Just for emphasis, anyone who thinks he’s listening to all the information that’s on the disc is badly mistaken. The scattered light problem itself without even going into any of the other problems associated with CD playback accounts for an apparent loss of at least 30% to 50% of performance, in terms of bass articulation and slam, treble performance, air, resolution and size of the soundstage, signal to noise ratio, dynamic range, distortion, compared to the case where scattered light is controlled. It’s not even close, gentle readers. Geez, even a green pen around the outer edge gives a glimpse of what you can get if you control all the scattered light, not just the visible red portion. Hel-loo! 

mapman
No reason to argue about how CDs work. It’s pretty well documented. Books are still an inquiring mind’s best friend.

>>>>Ah, good one, moopman! The old Skeptics Society chestnut. 🌰 Since everything is known and can be found in Wikipedia or some online textbook we can dismiss any inconvenient arguments as not worthy of examination. Bravo, moopman!

P.S. to my previous post:

I recall seeing measured data a few years ago indicating that erroneous reads by the laser mechanism occur vastly more often when ripping at high speeds than when ripping (or playing) at normal (1x) playback speed. Although even when ripping at high speeds the hardware will usually correct at least the vast majority of those errors bit-perfectly (assuming disc and drive are in good condition).

That would suggest, though, that if the particular ripping program being used cannot detect erroneous data and perform multiple re-reads as necessary, and provide an indication to the user if and when uncorrected errors cannot be overcome by re-reading at the particular speed, it would be desirable to rip at low speeds, e.g. 1x or 2x or thereabouts.

Regards,
-- Al

No reason to argue about how CDs work.   It's pretty well documented.  Books are still an inquiring mind's best friend.

erik_squires
I love that the OP has orphaned this thread, but people are still arguing about how CD’s work. :D :D :D

Yeah, I’m starting to think it might have been a drive by. 😬

almarg
IMO the reason many of the tweaks mentioned above by Geoff may be beneficial in some situations has nothing whatsoever to do with bit errors or error correction.

The main reason in most cases is likely to be related to electrical noise generated by the servo mechanisms and circuitry in the transport part of the player, as it tracks the disc, coupling into unrelated downstream circuitry in the player, causing jitter in the D/A conversion process, and/or intermodulation or other effects on the analog signal path. The degree to which that occurs will be dependent on the design of the particular player, of course, as well as on the condition of the disc.

>>>>Uh, I never said all the tweaks I mentioned affected bit errors or error correction. The ones I am pretty sure I can prove affect bit errors and error correction are New Dark Matter visible and invisible stray light absorption tweak, damping the CD (my Mystery Tweak) and coloring the CD, which absorbs visible stray light. Also, vibration isolation. All of those are my tweaks.

The demagnetizing of CDs and elimination static electric fields ON CDs is anybody’s guess. I don’t think anyone has explained them, at least not to my satisfaction.

note to self - I hate to judge before all the facts are in but it appears the Skeptics (capitalized for almarg’s benefit) would rather fight than switch. It certainly would not take a neurosurgeon or rocket scientist to do a little investigation and try to get to the bottom of these things. Isn’t investigation a primary part of the scientific method. And what about curiosity? Isn’t that part of the scientific method? Apparent it’s all too much trouble.

I love that the OP has orphaned this thread, but people are still arguing about how CD's work.  :D :D :D

Most of CDPs play in real time - there is no time to read particular sector again.  Ripping program can access each sector unlimited number of times to obtain right data (proper checksum).  Car or portable CDPs have to make up time to be able to return to troubled (bump) moment/sector and reread it.  In order to do this CD is rotating a little faster than necessary and the data is buffered.  I had once Panasonic portable CDP with a switch to enable/disable this mode.  I could clearly see thru the window CD rotating faster in bump-proof mode.  I'm only not sure what is considered a "bad data".  Reed Solomon code allows not only error correction up to certain number of missing data point (2.5mm scratch along the track per Al's post), but also data interpolation for a little longer scratches along the track.  CDs in really bad shape might still play fine, but a lot of data will be interpolated.  Ripping program can obtain right data to create new CD-R with better sound than original scratched CD.  I was even able to save that way few completely unreadable CDs (but it took long processing time).