Re: 384kHz PCM ???

John La Grou <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>...

> >IF YOU LIKE IT IT IS FINE. BUT PLEASE GET OFF THAT "EAR IS BETTER THAN
> >EE". .... IF I GIVE YOU A SCOPE PROBE AND
> >YOU SEE THE EXACT WAVE FORM IT IS ENDE OF CONVERSATION. THIS
> >ELECTRICAL WAVEFORM IS WHAT DRIVES AMPLIFIER AND THE SPEAKER. IF YOU
> >HAVE ZERO DIFFERANCE, THAN YOU CAN NOT HEAR IT EITHER.

> Too many times, I've heard two circuits with essentially "zero test
> differences" (THD, IMD, SN, SR, FR, CMR, PH, etc...) sound quite
> different.

Now, did you listen to them under blind conditions? If the measured
differences (there are always some measurable differences to talk of,
if you measure adequately) were much below known thresholds of
audibility of human ear, it's most likely it was just placebo effect,
or in other words, it was your brain knowing what you were listening
to, playing tricks in your perception. This is a very serious issue,
that is surprisingly taken in count very little times in the world of
audio.

There are fields of audio development where this is a fundamental
issue that is taken care of (by means of blind tests), such as
psychoacoustic lossy compression, just because it's fundamental for
efficient and reliable development.

Now, there's people that are convinced that there are audible
differences that can't be measured. I'm really skeptic about that, for
several reasons. First, because limits of human hearing are pretty
well known from several years ago. Second, because all kind of
distortions that can happen over an electric signals are known from
many years ago. Third, because measurement devices surpassed known ear
capabilities many years ago, by a very wide margin. And fourth,
because people claiming such things, usually have not performed a
controlled, rigorous, reliable blind test, that definitely proves
their claims. You know, as Carl Sagan said, "extraordinary claims
demand extraordinary proof", or something like that. Anecdotal
evidence, with sighted listening, or unexisting or poor time and/or
level matching, or very little repeatability is just not good proof
enough to take it seriously, and I've been witness of such things
happening relatively often.

> Some wise psychoacoustic-physicist types are attempting to
> find new algorithms to better correlate these subjective differences
> with repeatable / measurable metrics, such as:

But they always talk about both readily audible and measurable
differences. They just want to correlate better the measurements with
the perceivable degradation.
 
> Any linear function is subject to these illusive variables, including
> ADC front-ends (modulators, etc..). I'm not sure if this speaks to
> your argument, but certainly there is more to consider here than
> sampling theory and bench tests.  

Dan is just saying that sampling rate, by itself, can't be the cause
of audible differences. If there is really an audible difference, then
it must be somewhere else. I must add, one should make sure the
differences are not *outside* the equipment, thinking about things as
simple as slightly different output levels, or just the listener brain
influencing his perceptions.

I have personally degraded a piece of music extracted from a CD by
playing at recording it several times through an inexpensive semi-pro
soundcard, and challenged people to be able to tell it from the
original, under blind conditions, in a repeatable manner. Nobody, from
dozens of person, some with very good equipment, listening training
and ears, has been able so far, even when the degradation caused is
easily measurable. If you are interested in trying such a test, just
tell me, and I'll make it available for anyone that is interested.

Enrique G.