🚀 go-pugleaf

In article <753ar1$p8u$1@justice.csc.cuhk.edu.hk>, Kit-pui Wong
<kpwong@psy.cuhk.edu.hk> writes
>Some people with "golden ears" claim that there are great 
>differences between an original CD and its digital CDR copy.   

In theory, no, there should be no difference. The definitive way to
prove this is to first make a copy of a CD, and then get a favourite CD
player and hook the digital output up to a computer with a digital input
(SP/DIF etc). Then sample both the copy and the original and get the
computer to do a comparison. 

I reckon you'll find that they're 99% similar. 

>Is there any **theoretical** ground about the difference ?  
>In digital world, information on CD are always O's and 1's. 
>A digital copy of an audio CD should store the same stream
>of 0's and 1's and therefore produce exactly identical 
>output. 

That's right. Having said that, there are mitigating factors inherent in
the way the digital signal is read from the disc. A dirty disc, or a
poor quality CDR (it would have to be very poor quality) will mean that
the error correction circuit in the CD player has to do more work to
play the CD properly. Some manufacturer's error correction circuits are
better than others. Weirdly, my �200 Pioneer CD deck refused to play a
certain rather badly scratched CD without a lot of skipping, but my
sister's cheapie yucky Amstrad micro system managed it. That's life.

>Then, what makes the differences (if any) ??

People hearing a difference because they are expecting one. I get a
great laugh bringing audiophiles around to a friend's studio and running
their favourite LP's through an analogue-digital converter hooked up
directly to a digital-analogue converter with a bypass switch, and
seeing if they can spot when they're getting the "pure" signal or the
digitized one. Most of the time they get it wrong.

-- 
        Brendan Heading
http://www.heading.demon.co.uk (updated every Thursday)
ICQ : 24010538
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"The appeal to patriotism is the last refuge of a scoundrel"