[time-nuts] Oh dear

[Chris Albertson]

On Mon, May 7, 2012 at 11:15 AM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:

> We must start out by defining the acceptable level of total distortion,
> if we choose 0.5% then we need 200 digital levels, roughly 8 of
> your 16 bits for the signal.
>
> That gives you a headroom of 7 bits (leaving one for the sign) and
> that gives you 42 dB of S/N.
>
> That isn't very much, headroom, 42dB, when the conductor waves the
> entire philharmonic AND the full opera choir in, for for that wonderful
> "Dies Ira" of Verdis.  Or Carmina Burana.  Or any of the many
> other 'shock-effects' classical composers have enjoyed.

You are mixing recording and distribution.  The 16-bit 44.1K "CD
Quality" is for distribution to consumers.  Few people record with
that format.  24-bits and 96K is a common recording format.  and then
later it is mastered to "fit" within the CD format.    And don't
forget that some tools the mastering engineer has are EQ, "dithering"
and frequency dependent compression.  It is VERY rare that a
performance would be linearly transliterated to the CD.   What you get
is something that was modified to sound good on consumer playback
equipment.  With "good" being the engineer's person opinion.

Back to recording.   It is common to have the master studio clock be
an OCXO.  This would drive the (96K) sample clock and it is the sample
clock that gets distributed inside the rack.   My cheep home system, I
think has a low cost XO inside and is pretty much jitter free.  Simple
XOs can be pretty good especially what you care more about "clean"
than accurate

Chris Albertson
Redondo Beach, California