Re: Audio Sampling Question


"Tom Bruhns"


Well, I'm glad to see that you apparently agree that protection
against aliases, however you do it, is a good thing. Clearly, if my
input has only "audio" frequencies in it, I don't need an alias
protection filter if I sample directly at 44.1kSa/s. You may have the
luxury of dealing with systems in which there is no explicit need for
an alias protection filter; when I was designing with delta-sigma
"audio" converters, I didn't have that luxury. You may even have the
luxury of not having to consider the effects of a first-order filter
with 75kHz cutoff at frequencies below 20kHz, but I also did not have
that luxury. Fifteen degrees phase shift (at 20k) is huge when you're
reporting phase to millidegrees. Even the 40dB attenuation of that
filter by 7.5MHz is inadequate when you're dealing with systems whose
input you guarantee to your customers to be protected against aliases
to 100dB. It's nice to live in a world where you don't have to worry
about little details like that, but in my world, I have to pay
attention to such details.



** Bruns lives in the " world " of charlatans, con-artists, criminal
fraudsters and the biggest the scumbags on the planet.

He feels very comfortable in that world.

FYI

- it is the world of lunatic fringe audiophools and the pimps that live off
it.





......... Phil


.

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