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Re: Questions for audio gurus

Subject: Re: Questions for audio gurus
From: "Julius Thyssen" <>
Date: Thu, 23 Feb 2006 20:32:26 -0000
> Am I correct that what you discribe as anti-aliasing artifacts will
> vary dependent on the quality of your a/d and d/a converters?
> Rich

Yes, on A to D conversion quality mostly.
The basic intention of anti-aliasing is to filter
out all frequencies that are out of range for
the digital part of the sampler/recorder;
A lowpass filter. It lets frequencies go through
below a transition area. You need to do this in analogue.

For example, if you sample at 48 kHz,
this will take in audio up to 24 kHz (or 23.999 Hz more likely).
The lowpass filter needs to make sure there is no
( or VERY little ) audio higher than 24 kHz coming in.

- Some filters use a very wide transition band,
with a neat slope going down from 18 to 24 kHz.

- Some filters use a small transition band, with a very
steep filter, going down from 23.800 Hz to 23.999 Hz,
the latter often causes such a filter to also affect
lower frequencies. It will unintentionally have tiny
band-notch EQ 'ripple' effects on, for example
10, 12, 14, 16, 18 and 20 kHz. You don't want that,
but you will also not notice it very much.

Good info on this can also be found on:



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