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Re: Re: freq response and aliasing of Edirol FA-101 (and FR-2) at =

Subject: Re: Re: freq response and aliasing of Edirol FA-101 (and FR-2) at =
From: Gianni Pavan <>
Date: Tue, 11 Jan 2005 09:26:10 +0100
192 kHz

Hi Rudy,
        many people on this list will be interested in knowing more about the 
FR2=

frequency response and about its mic inputs' noise! Did you test other 192=

kHz devices ? Perhaps the 722 ??

I'm not sure you're completely right about a-a filters.
In consumer products the overall response is due by the combination of the=

analog bandwidth and a tunable filter that is mostly aimed at reducing
aliasing by cutting frquencies above Nyquist.
In a 192 kHz system the analog bandwidth should be 100 kHz or more and thus=

a filter working for 48 or 96 kHz sampling can't benefit of the analog
roll-off.

Though, well designed filters can cut sharply close to Nyquist without
being affected by the analog bandwidth of the system. In high-end boards,
the Lynx boards for example, you get a sharp and clean cut-off regardless
of the sampling rate: just the same performance at 48, 96 and 192 kHz.

In the FA-101 design, probably Edirol engineers assumed that normal musical=

programs received by normal microphones can't have frequencies higher than=

50 kHz and thus they adopted a very soft filter without considering other,=

more critical, recording needs.

Any further thought on this topic will be appreciated,
Gianni
--------------------------------------------------------------
Gianni Pavan
Email 
Centro Interdisciplinare di Bioacustica e Ricerche Ambientali
Universita' degli Studi di Pavia
Via Taramelli 24, 27100 PAVIA, ITALIA
Tel        +39-0382-987874
Fax        +39-02-700-32921
Web       http://www.unipv.it/cibra



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