From: sss@castle.ed.ac.uk (S S Sturrock)
Newsgroups: rec.audio
Subject: Re: Forget the DACs. How can transports sound different?
Date: 21 Jan 93 13:44:14 GMT
Organization: Edinburgh University

In article <shetline-200193103810@128.89.19.74> shetline@bbn.com (Kerry Shetline) writes:
>In article <30486@castle.ed.ac.uk>, sss@castle.ed.ac.uk (S S Sturrock)
>wrote:
>> More to the point the DCC transport is very likely to affect the sound
>> quality in much the same way as a CD transport so even if they are both run
>> through the same DAC you still can't state unequivically that the
>> difference in sound if there is one is due to the compression.
>
>Oh, you mean no effect at all? :-)

No, just that until all other effects are accounted for the compression
cannot take all the blame (or credit) for the particular features of the
sound quality.
>
>> double blind testing is needed to get the stage where the finger can be
>> pointed with any level of certainty at the compression, but only if the DAC
>> used for both sources is the same one.
>
>Yes. And please put these highly doubtful claims about transports to the
>same test. Even all of this talk about jitter doesn't seem to leave any

These `claims' have been highly tested, differences in transports are well
documented.  They are due to deviation from the standards set down for
various reasons.  Rise/fall times of the pulses in the SP/DIF data stream
are known to affect the sound significantly.  Incompatibilities in the
amplitude of signals used/expected between transport and DAC can adversely
affect the sound.  These came to light when it was shown that a DAC may
work very well with one transport and not with another yet the transport it
worked poorly with would work very well with a different DAC.  I don't have
the reference with me at the moment, I will check for them at home.

>place for suspecting transports. If their is any jitter effect at all, it
                                     ^^^^^
                                     there

>seems to be in the DACs. I've not heard one report of inconsistent or
>jittery timing of data coming from a transport. (Maybe I've just missed

You should read more.

>such a report, but it seems unlikely since high-quality consistent data
>timing is easily and cheaply achieved.) Here we go again... If the bits are
>the same (a reasonable assumption, since CD error rates a typically *very*
>low), and the timing is the same (again a reasonable assumption), what else
>but some difference in the mechanical sound of a transport is left to make
>a difference?

See above and the references I will hunt out tonight.
>
>Without a good explanation, I'd still be forced to accept that transports
>can sound different if well conducted A/B tests would show that people

Such tests have been performed in true double blind conditions, again I
will find the references.  The tests on the transports were done as a
result of the double blind testing to find a reason for the differences in
sound of transports partnered with various DACs.

>could consistently hear differences between transports. But with no such
>data, and no good theory, the anectdotal 'evidence' is hardly compelling.
>Under such circumstances, the idea that transports sound different is a
>mere conjecture, not something to be bandied about as proven fact.

I will provide you with the references, even the conclusions if I can spare
the time to type them in.

Hopefully that will lay this argument to rest until the next influx of new
subscribers and we have to go through it all again.



-- 
Shane Sturrock, Biocomputing Research Unit, Darwin Building, Mayfield Road,
University of Edinburgh, Scotland, Commonwealth of Independent Kingdoms.  :-)

Civilisation is a Haggis Supper with salt and sauce and a bottle of Irn Bru.
Newsgroups: rec.audio