[LAU] 1980's cds: analog to digital conversion

[Monty Montgomery]

On Sat, Feb 13, 2010 at 5:10 PM,  <fons at kokkinizita.net> wrote:
> On Sat, Feb 13, 2010 at 03:07:21PM -0600, Brent Busby wrote:
>
>> It seems that with CD's, you're cursed one way or another nomatter what
>> era they come from.  In the 80's CD's, you have the gritty metallic
>> sound that comes from inappropriate EQ that was mentioned,
>
> If that were the real problem then applying the inverse
> EQ would solve it (and you'd gain some S/N ratio as well).
> Try it and you'll find it doesn't work that way.

The RIAA preemphasis is not a biorthogonal filter.  There will always
be at a minimum some phase/group delay as the 'perfect' inverse filter
is unstable.  You can only approximate it.  Another example of an
analog horror we no longer need to put up with in the digital era :-)

A digital EQ alone isn't even close, as digital EQ is nearly always
phase-linear (acausal).  It's a completely different style of filter.

Also, the preemphasis is only part of it; mastering engineers of the
day mixed and mastered for the medium, so they did a bunch of things
that only make sense for vinyl.

Monty