CD reflective layer quality in regards to performance

I bought a brand new autographed CD once that didn't play. I held it up to the light and it was transparent, totally missing the aluminium layer! Took it back to the store and got a replacement but it was the weirdest Cd I've ever seen. Think this was around 1998

 

I borrowed an original pressing of Synchronicity that was absolutely battered, and had a gigantic hole in the aluminum layer (more like damage from abuse than a naturally occurring pinhole) right over the 1st track. I didn't expect it to work, but somehow the whole disc ripped perfectly and the error correction never kicked in once. CRC tests matched and accurate rip verified. Color me shocked. I don't think it would have played through in a transport designed for real-time playback.

 

Thanks for your input in letting me know your experience with your CDs. The more people post about this seems to indicate that the issue is only cosmetic and does not affect the playback quality of the music.

 

What everyone else has said. I've seen CD's that look horrible and rip perfectly. I also have CDs that look perfect and will barely play if at all.

 

I have a mint copy of Alan Parsons - On Air CD that looks totally flawless but will not track on my CD player. It jumps and skips around the whole album in no specific pattern.

 

With regard to the reflective layer, the only issue is whether it returns sufficient light to the photo-detector to allow 'slicing' to occur. If you can rip/play the disc with no problems, then there is nothing to worry about. As ffracer mentions, the infra-red laser used for CD 'sees' the disc differently to us. What may appear to be an aberration to you may not be an issue in the infra-red spectrum. Moreover, as mrdiscman points out, reading of a CD is nothing like the reading of a vinyl groove. The audio data sample values (the 16-bit audio words) are NOT written to the disc directly. CD uses a complex offsetting/interleaving/re-coding (EFM) scheme to overcome channel problems (scratches, fingerprints, etc.). The data making up each audio sample is widely dispersed over the disc, and it is only after a large block of data has been read, de-serialized, de-interleaved, and error corrected (if necessary) can you get back to the audio sample values [I've never understood the fuss about buffering with regard to CD playback, as it is impossible to decode CD without suitable buffers!]. CD is very robust! Remember, you can drill holes of a millimeter or more in the disc, and still recover the data 100% correctly!!

 

Thanks for the resourceful info.

 

For the most part, do not worry. In ~99.99% of the time, swirls will not even engage error correction. Playback quality will not be affected.

 

Electrical errors are simply data stream errors. Some examples are C1 errors, C2 errors, and elevated block error rate (BLER). This is all defined in the CD Redbook.

Swirling should not be a worry. If you have a choice between a used CD with swirls and the same used CD without swirls, take the one without swirls. But if the swirled CD is less costly or it is your only option, by all means buy it. The swirls will not affect playback.

 

Thanks again for all the info and explaining things to me.

 

In 25 years of CD usage I've only ever had two CDs with pinholes and two with CD rot.

The two CD rotters were The Jayhawks Hollywood Town Hall and Pulp's His 'n' Hers

The Pinholes are CD2 of The Best of The Doors (early 90's issue) and an original version of Terry Reid's The Driver.

Lots of swirls and stuff, never caused an issue. I doubt the laser is troubled by it.

 

I have bronzed and pinholed cds but so far they play OK.

 

Indeed "more". I recall when John Atkinson (Stereophile) tested the Playback Designs MPS-5:

"Until the MPS-5, the best error correction I had encountered was from the dCS Puccini (reviewed in December 2009, which also uses an Esoteric mechanism), which didn’t suffer from glitches in its audio output until the gaps in the data spiral of the Pierre Verany Test CD reached 3mm in length. The MPS-5 exceeded that, playing through 3.5mm gaps in the data, and not suffering from occasional mutes until the gaps reached 4mm. Astounding performance!"

 

I have a few CDs with pinholes, some large ones too, but no payback issues.

 

I have four UK PDO discs that are bronzing, but still play fine since I last checked.

 

Yeah, that Esoteric transport mechanism on its own is more expensive than many CD players!! One would hope it could cope with a few blemishes, but 3.5 mm gaps, that's pretty special.

Rip them NOW!!!!!!!!!!!

Trust me, they will eventually become unplayable (if they actually are from the affected series of discs from PDO Blackburn). I speak from experience!

 

Keep that disc as a test disc! I have a Led Zeppelin original issue with a few big 'pinholes' and you'd be amazed at the different level of 'correction' different players exhibit. My $799 NAD C565BEE threw up on every hole, while my $139 Onkyo C7030 didn't flinch! (????????) So you really can't judge a book by it's cover. $139 player beating the pants off of an $800 player, I bet you NAD wouldn't want to know about this.
the beave

 

I used to test my new players by putting a tapered piece of tape on the surface (used my target Avalon at the time (GAH! )) and my first CD player has been the by far best one to cope with defects, the Philips CD 202. It could take up to 5mm wide defect without skipping or being audible. It had superb reading performance and interpolation ability. Of course it had the metal laminated pivot mounted laser pickup arm with glass lens and such stuff that all the early Philips had. A wonderful drive from an engineering standpoint.

None after that have come close, though the Yamaha CDX 1030 were pretty good and second best so far. My present Pioneer PD-S901 is also really good, but still inferior and I fear the new Marantz CD6005 which arrives this week will be at the bottom if user reviews are anything to go by. Thankfully, most of my CDs are in really good condition.

I have some PDO discs but they haven't begin bronzing so either the climate is kind up in northern Sweden or they're aren't of the affected batch.

 

Between Mr.Discman and Black Elk (thanks for chiming in with your expertise!) and others here, there are plenty of people here on SH who actually have first hand experience with the technology from the companies who provided it. i.e. they either contributed to the design or engineering or worked in the facilities.

The CD format is amazingly robust as Black Elk put it. Like any product, there are companies who made some errors or defects for a short time. In the CD's case, this is a small number of companies and for a limited time. The point is the number of defective CDs made is so small in the % of all CDs made, it really is almost a non-issue (<0.00..1%!) and these problems are well documented here and on the forum (PDO UK bronze, Discovery Systems, etc.).

Compared to LPs, cassettes, or most consumer electronics, the defect rate and longevity failure is staggeringly near zero. Really remarkable when you think about it.

 

Wow. This is terrific info. Thanks for sharing with us.

By the way, would it be correct to state that the less the error correcting mechanism is stressed, the better? And thus mint discs actually help preserving CD players while scratched/damaged ones are somewhat able to wear them out? Just curious. Thanks!

 

In my opinion, no, since discs are allowed to leave the production line with a correctable error rate of 220 PER SECOND!! While the real rate will be much lower than that (and the uncorrectable rate must be zero), it does mean that the error correction circuitry is needed even for minty new discs.

I go into things in more detail in this post: http://forums.stevehoffman.tv/threa...king-in-cd-fallacy.255665/page-8#post-6790567

but you may want to read through the entire thread, it is very interesting. (Forum member crapfromthepast, who responds in that thread, worked in CD manufacturing for many years.)

 

Thank you very much for taking the time to reply; much appreciated. I'll read that thread; thanks for the link, too!

 

Interesting hearing about your CD tests. Error correction does it's wonders. I know what you mean about CD players as well. My first CD player I got for Christmas in 1987 was the best I ever had. It was a Sanyo (under $200) and had a sticker on the back with the manufacture date 1986. The next two players I got were cheaper but inferior. The last thing I bought was a cheap ($35) Memorex DVD player and the sound was tinny. I'm now using my brothers Yamaha Natural Sound CDX-450 which has great sound and very minimal problems with skipping.

 

Some porn for all you die-cast Philips CDM transport fans: http://www.dutchaudioclassics.nl/?strPage=Info&strBrand=Various&strType=PhilipsCDM

 

I own many CDs with swirls in the polycarbonate and all of them play without any issue.

Last week I happened upon a new copy of the deleted The Eurythmics Sweet Dreams (Are Made of This), RCA catalogue number ND 71471 in my local JB Hi-Fi. When I got it home and opened it the disc had a couple of small scratches in it towards the later tracks on the disc that were in the aluminium layer as opposed to the polycarbonate but the reflective layer itself was quite speckled in appearance. It looked like it had measles and appeared second hand even though it was new. In 30 years of buying CDs this was the first disc I have bought that had to be returned as totally faulty. It took a long time to load in each of my Technics SL-P999, a Denon DVD-3930 an Opp BDP-83SE and the blu-ray drive in my laptop struggled to even see it in both EAC and iTunes. It would not start to even begin in rip in either program and in every player above it either skipped during the first track (despite no obvious blemishes in the inner parts of the disc) or skipped straight to track two. I tried taking photos of the disc but couldn't get the blemishes to be apparent in the photos.

The only other disc I have ever had to return was in the early 90s when a disc had a large click in one song that was a pressing problem as it was not evident on the replacement copy.