From: ketil@edb.tih.no (Ketil Albertsen,TIH)
Newsgroups: rec.audio
Subject: Re: How can different digital cables sound different?
Date: 6 Jan 93 15:15:29 GMT
Organization: T I H / T I S I P
Posting-Front-End: Winix Conference v 92.05.15  1.20 (running under MS-Windows)

In article <184780@pyramid.pyramid.com>, lstowell@pyrnova.mis.pyramid.com (Lon Stowell) writes:

>   [..] errors DO occur on
>   optical media.  What counts is whether the actual errors are less
>   than the "span" of the error detection and correction
>   algorithm...or whether a higher layer is able to correct the
>   error with sufficient speed to paper over the errors which do
>   occur.  "errors don't occur" and "errors are truly random" are
>   famous last words in data comm.   

Sure bit errors occur. My point was that for all practical purposes,
the error detection/handling IS advanced enough to cope with those
that do occur.

In anoter posting, igb@fulcrum.co.uk (Ian G Batten) wrote:

>But the error correction used by the CD drive or DAT machine has been
>done long before the bitstream is passed over an SPDIF or AEU/EBS
>interface.  There is no error correction on that link.

Well, I didn't know that, but I am not surprised. BUT: To improve the
quality on real time data transfers, retransmission is not the way to
go unless you have a lot of excess channel capacity. Otherwise, it will
be just too late. Error correcting codes will be a much better bet.
Sure, that causes overhead even on successfully transmitted data, but
we are talking real time information here. That is definitely different
from an FTP transfer!

>   [...] And since the
>   discussion was about CABLES, not pulling data off the media, I
>   fail to see what a scratched CD has to do with it.  

Only to illustrate how retransmission would not solve the problem.
(There is no really significant difference between reading data off
a cable or receiving them from the disk.)

>>The true question is: Given two digital signals that are *exactly
>>identical* at the point where they are joined (e.g. at the DAC input),
>>can a trained ear *still* hear the difference? Evidence is that
>>that is possible.
>
>  You lost me here....could you expand a bit?  Do you mean DAC's
>  sound differently, or that identical signals into the SAME dac
>  would sound different?   

Maybe you didn't hear my sarcastic voice... If the part of the signal
chain chain following the digital cable (DAC, amp, speakers ect.) is
not changed, the sound produced depends solely on the input. For a 
digital signal, the input is nothing but 0s and 1s having no other
qualities than being 0s and 1s. If the same 0s and 1s come from two
different sources, but are the same 0s and 1s, the input to the
DAC/amp/speakers is identical. Unless the phase of the moon has
some effect on the electronics, the sound will be identical, too.
At least if analyzed by neutral means. I mean, this is a fact -
you can't argue a fact.

Then comes a certain group of audiophiles, saying like that scientist
a while ago (I'll find a reference to the source if anyone cares!):
"Yes, I know it is a fact, but at the moment I prefer not to take it
into consideration". And they add that there still is a quality 
difference of the sound that, although not supported by facts,
nevertheless is audible to them. OK, I don't believe in them, but
I don't believe in angels or ghosts, either.