CD transports and resonance
mick wrote:
I read somewhere (sorry, can't give a ref) that the error correction on
transports intended for audio is more lax than on those intended for data,
as your ears are incapable of detecting low error rates but are more
sensitive to the gaps caused by error correction. If that is so, then
using a data drive for audio may give a different sound, but not one that
is necessarily "better" as it will contain a different sort of inaccuracy!
I'm sure someone will be able to correct me on this if I'm wrong.
There's a lot of error correction capability on a CD. Hamming encoded IIRC.
Forget how many bits of error it can correct transparently. Philips / Sony
expected early CDs to have lots of errors so needed them to be correctable.
Bear in mind that it was expected that early CDs would *need* error correction.
I'm sure they are much better now.
I can't recall if the CD standard includes 'error concealment'. Anyone know ?
The German broadcaster WDR ( IIRC) found that subjective differences between
*DAT* transports was due to head misalignment causing error concealment to kick
in. Some units suffered more than others. Error *concealment* kicks in when
there aren't enough valid bits to transparently *correct*.
Error *concealment* is *not* audibly transparent.
I doubt that CDs are troubled by this though.
Graham
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