Physical degradation of CD's


Hello friends,

Please keep in mind that I am new to the digital world and I'm just curious about something....

I have just recently bought two Dac's.  As I've been trying to break them in, I've had a cd player spinning a cd 24/7 on repeat into the dac.

I'm wondering, does the cd laser constantly going over the same pits over and over again, somehow degrade the physical aspect of the cd layer that is being read by the laser?

I know that I wouldn't want to replay my precious vinyl over and over again, but in that case I'm physically dragging a diamond stylus through the record grooves.  

I have no idea if the laser does anything to the bits it's trying to read when kept on 24/7?

Thank you and best wishes to you all,

Don

no_regrets

Many years ago, when I was a contributing editor to various mainstream tech publications, I did a large feature on disc rot. Spoke at length with engineers, large manufacturing & fab facilities, the whole nine yards. At this point, I don’t remember where it was published, maybe PC Magazine.

The bottom line is that "CD rot" today is pretty friggin’ unlikely. There were reports that the first generation of CDs were subject to this problem, and it was eventually traced back to a single disc-fab plant, I think in Europe, that was a source for discs worldwide. The issue was an improper seal that allowed air to contact the aluminum layer, causing black oxidation. This, of course, changed the reflectivity of the pits & lands, making parts of the disc unreadable. Most people I spoke with believed that this happened only when the disc was flexed or otherwise abused to the point of breaking the original seal. My conclusion was that this was an exceedingly rare occurrence, very much overplayed in the press.

Note that I’m talking about replicated discs. Home-recorded recordable CDs, for some reason, are much more susceptible to this problem. But again, it seems as though the issue was mostly with earlier generations of recordable media and, even in worst case, it would take years to manifest. Much more common than silver-disc "rot", but still pretty rare. My personal opinion (and it's just an opinion, not something I can verify) is that the greater number of problems with recordable CDs has more to do with the fact that they use potentially degradable photoreactive inks.  But at this point, who knows?

This shouldn’t be confused with "DVD rot," which was technically similar, but much more common. DVDs are composed of multiple layers of plastic glued together, and are thicker. In terms of physical structure, they’re more susceptible to damage by flexing. This problem was exacerbated by early DVD jewel cases, which made it more likely that unthinking users would flex the heck out of a disc while trying to pry it out of the case.

Again, this was a problem related to early manufacturing issues, that were later worked out. And although more common than "CD rot", which borders on urban legend, it was still pretty rare.

I have examples of "rotted" discs still sitting on a shelf somewhere. If I get the chance, I’ll take some pictures & post them here so you can see what "rot" looks like.

Never ever had an issue with my CD’s. That is, until right after this thread was posted!

Last night played "Miss Saigon" and heard this low level crackle/static noise. At first thought it was my electronics. Thankfully other CD’s played fine.

FWIW, the CD visually looked pristine. Odd.

Update. I played this CD on a second system with the same result. This background noise could be best described as what you would hear with a really dirty old abused LP. The second CD of this box set played fine.

Interesting.

I owned a small recording business and would routinely furnish my clients with copies of their performances that were burned with a pro level CD recorder. On rare occasion I would get a complaint of "drop-outs" on the disc.  At first I attributed it to the clients using an inferior machine for playback but I finally traced it back to the discs themselves.  That is when I switched exclusively to "Archival" quality CDs.  The phthalocyanine dye or ink used on these discs is remarkably stable and even extended periods of exposure to sunlight will rarely cause them to default. Since making that switch, I have only had one problematic archival disc and that was one that refused to initialize.  Have I checked every disc I made since then ?  Of course not, but I've received zero reports from clients that the disc performed poorly.  I'm sure that stamping a disc is more reliable than burning a disc but that is what we have available at present.