16 Jan
2005
16 Jan
'05
1:43 p.m.
I guess the antialias filter starts rolling at around
20, and uses all
the extra bandwith to avoid making the filter steeper and messing the
'audible' audio. Just a guess. I would guess most music recording
interfaces do this.
I realized why they do this. With variable sampling frequencies,
44.1, 48, 96, you would need different filters to get the best out of
each one. So they just do 20 once and throw away the extra bandwidth.
So does that mean they will alias at sampling rates like 11025? This
could be tested, too.
18 Jan
18 Jan
11:57 a.m.
Interesting.
I did two measurements @96000, first with a tone sweep, and then with
white noise. The results were:
Tone sweep:
www.geminiflux.com/Stuff/snapshot1.png
White noise:
www.geminiflux.com/Stuff/snapshot2.png
The card being use was Echo Mona Laptop, the microphone a Shure Beta58
(which might account for the weird behaviour), and the speakers were
Mackie HR824.
I'll give it a try next week with a better microphone.
Cheers,
Andres
Jon B wrote:
I guess the
antialias filter starts rolling at around 20, and uses all
the extra bandwith to avoid making the filter steeper and messing the
'audible' audio. Just a guess. I would guess most music recording
interfaces do this.
I realized why they do this. With variable sampling frequencies,
44.1, 48, 96, you would need different filters to get the best out of
each one. So they just do 20 once and throw away the extra bandwidth.
So does that mean they will alias at sampling rates like 11025? This
could be tested, too.
7292
days inactive
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Jon B