OFF: CD Rot

[Jon Jarrett]

On Mon, 18 Oct 2004, Henderson Keith wrote:

> Well, this is in a way on-topic, but only coincidentally.
>
> So, I put on my Virgin (1989) Quark, Strangeness, and Charm CD on the other
> day, and discovered to my horror, that it is 'going bad.'  I don't know much
> about the CD rot phenomenon (as I've never had this happen before), but I
> suppose this must be it.  It's got a heap of crackly noise at the outset
> during the first bit of SotA, but that quickly dies out when the real song
> kicks in.  But then it slowly creeps back toward the end of the album,
> starting again around Days of the Underground.  Never gets as bad as the
> first two minutes, but it's enough to be distracting.  And the noise is
> louder when the music is louder, and vice versa.  It seems strange that it
> appears to creep in from the edges on both sides, but in non-uniform way.  I
> mean, the noise propagates just a tiny distance in from the center ring (the
> beginning) through (apparently) the 'Table of Contents' and the first two
> minutes only.  But because QSC is 'short' (42 minutes or so), it has a wide
> ring of unused disc space, and the 'rot' seems to have already crept from
> the far edge across this empty zone into the last cm or so of actual music.
> Or am I reading too much into this pattern?

        I've had symptoms like this with a few discs here and there, but
it's never been lasting, ad I've always put it down to the discs being
slightly unbalanced. My first CD player was terribly sensitive to this,
and my second didn't have enough clearance in the compartment so you did
know about it when a disc wobbled because its edges would tick against
the casing! But in more substantial machines, this seems to be audible as
a rhythmic static-type fizzing background pulse, which gets louder when
the music does and quieter likewise. It's more pronounced at the ends of
the disc for obvious reasons, but usually it's also something to do with
the ambient temparature and doesn't occur generally. It does sound as
though keith's disc is actually decaying but I feel I should warn against
all such phenomena being permanent.

        Weirdest thing I've seen in this line, or rather heard, was last
time Sherman and I were working on Larry Boyd's Disarray stuff. The `first
album' we have now put together was generating test discs (burnt through
Nero using files created in Cool Edit) which were full of unlistenable
crackly fizz. On one machine only. We burnt a second one and the effect
had got worse, as if delay had been applied to it. But the blaster in the
kitchen played them absolutely clean, while two computers' CD drives and
soundcards picked up a tiny fragment of crackle but no more. We couldn't
figure out what on earth had happened to the files that made it so
disastrous for just this one player... Yours,
                                              Jonathan

--
                Jonathan Jarrett, Birkbeck College, London
    jjarrett at chiark.greenend.org.uk/ejarr01 at students.bbk.ac.uk
  "As much as the vision of the blind man improves with the rising sun,
       So too does the intelligence of the fool after good advice."
       (Bishop Theodulf of Orleans, late-eight/early-ninth century)