Walt wrote about reading Pohlmann,
>I'm still working my way through sections of the book. And this section
>I need to reread a few more times to get it all. But, if nothing else
>he's definitely saying that anything like true 24 bit accuracy is going
>to require a extremely high quality A/D section. Something that's not
>too likely in lower price points. Makes me wonder about the inexpensive
>stuff claiming 24 bit. They may be producing 24 bit, but not doing it
>accurately.
It's like when digital recording started. The code was 16-bit, but
the A/D converters were only good for 13 or 14. 13 bits was as good
as the best analog tape (w/o Dolby or dbx) and had lower distortion
and flatter frequency response. It was problematic when quiet
environments failed to dither the lower bits, and low-level sounds
were munched or dropped out. I have a CD from the early days that has
that problem.
In a few years 14-15 bit converters were available, and we learned
how to dither. Digital came of age and left analog in the dust.
Now with 24 bit codes we again are working with converters that don't
really deliver the whole range of the code, maybe 21 bits of audio in
a 24-bit word. But 21 bits makes a dynamic range of 126 dB, and -any-
environment or preamp noise will dither those low bits.
-Dan Dugan
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"Microphones are not ears,
Loudspeakers are not birds,
A listening room is not nature."
Klas Strandberg
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