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

Monty Montgomery xiphmont at gmail.com
Sun Feb 14 11:51:06 EST 2010


On Sun, Feb 14, 2010 at 6:31 AM,  <fons at kokkinizita.net> wrote:
> On Sat, Feb 13, 2010 at 10:16:24PM -0500, Monty Montgomery wrote:
>
>> I'm aware of how to construct digital IIR filters :-)  I was hoping
>> you had a URL to a nice official analog topology.  The specific
>> implementation details matter.
>
> I'll make a nice drawing later. Right now I have
> to finish my LAC paper !!

Uh, I was hoping for an official recommendation from the spec, not an
intuited circuit that works.  I didn't know of any officially
recommended one, but the way you were talking about it, I thought you
did. Either from the original only sort-of-standard RIAA curve or the
eventual IEC specced version.  I don't need a schematic of a simple RC
bandpass, thanks :-)

>> > The channel EQ you'll find on most digital mixers is
>> > not linear-phase at all, nor acausal.
>>
>> OK.  Time to become incredibly overspecific:
>>
>> Every digital EQ implementation I'm aware of for Linux is linear
>> phase.  I wrote a few of 'em.
>
> The only examples I know of are the FFT based EQ
> in Jamin, and the octave band filters that come
> with jconvolver.

Uh, those are linear phase and acausal.  Also beware of JAMin's using
the FFT for non-time-invariant effects, it will modulate the audio
that passes through.  Not a problem for FFT, huge problem for things
like compressors.

Monty


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