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Re: Sample Rate Conversion

Subject: Re: Sample Rate Conversion
From: Walter Knapp <>
Date: Tue, 11 May 2004 20:32:43 -0400
From: Rob Danielson <>

> Sorry if this  suggestion has been made.  Don't you think the D->A
> used for monitoring is a big factor? (The type of native dsp (digital
> sound processing) in one's computer or the external audio card.)
> I've experienced huge playback differences between cards and native
> dsp with the sort of sounds Lang supplied.  Indeed, cheaper CD
> players can do an awful job of reproducing such sounds even if the
> data on the CD is fine. D-A quality was one of the  conclusions
> reached when the insect distortion question was explored a couple of
> years ago.  As to how to get them to play on CD, the only trick I've
> found is reducing the dominant Hz's above 8K with sharp eq and
> keeping them low in the mix. Something to do with the envelope shape
> it seems.  Rob D.
>
>

Since we are first converting to a set sample rate and then playing them
to compare, I'd think the D/A would be a factor but not as big. Assuming
the conversions produced close to the same result they should play the
same. However, many pieces of software have various settings that seem
to feed that D/A differently even for the same sample rate. A lot of the
stuff I've mentioned fits that layer in the software chain. There are
hardware differences, Vicki's iMac definitely has a different set of
audio hardware from my G4, for instance. And the software driving that
hardware is different too.

I should also note here that I can find differences in the low level
sounds in the various conversions using a sonogram. So the D/A is
putting out differences that were in the files. In particular the
original Peak and Soundhack conversions added a lot that was not in the
original. Since those additions are primarily in frequencies below 5khz,
where everyone can hear better (have greater sensitivity), even pretty
small changes can mask the wanted high frequency sound.

Walt




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