[LAD] Xiph.org - Video:Digital Show and Tell - No difference between analog and digitally processed sound.

John Rigg ladev6 at jrigg.co.uk
Thu May 23 14:30:46 UTC 2013

On Thu, May 23, 2013 at 12:18:25PM +0000, Fons Adriaensen wrote:
> Take a filter for a 48 kHz DAC. It could be -0.5 dB at 23 kHz,
> -12 dB at 24 kHz, and -100 dB at 25 kHz. Any aliasing will be
> either above 23 kHz or below -100 dB, probably harmless.
> Given the passband and stopband constraints at 23 and 25 kHz,
> the actual value at 24 kHz is more or less irrelevant.
> The potential intermodulation effects referred to in the paper
> by Julian Dunn are real, but not realistic. If such signals 
> (high energy well above 20 kHz) are present you'll have some
> serious problems even in a completely analog system.

True, although I'd have more confidence in a filter that eliminated
the possibility entirely.

I couldn't resist responding to the statement in the thread title:
"No difference between analog and digitally processed sound".
As in so many things, "that depends".


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