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Re: Tascam DR-680 specifications again

Subject: Re: Tascam DR-680 specifications again
From: "Raimund" animalsounds
Date: Tue Apr 13, 2010 1:34 pm ((PDT))
oryoki wrote:

> The Tascam folks were surprised by Dr. Specht's test results.  They claim=
ed that the low cut filter and limiter were analog functions that take plac=
e before the digitization process.

Hmmm, but as Paul already mentioned, the block diagram published by Tascam =
also clearly indicates that the low-cut filter is located in the digital do=
main. See the manual (http://www.avisoft.com/DR-680.pdf) at page 55.

So, I'm a bit confused.

Maybe the Tascam folks meant the (fixed?) high-pass filter on the analog in=
put that usually consists of a simple capacitor (in combination with the in=
put impedance of the op amp), which isolates the 48V phantom power from the=
 OP amp input. This analog high-pass filter is usually responsible for the =
low-frequency limit of the recorder (20 Hz at -1.5dB).

However, we were talking about the adjustable (40, 80 or 120 Hz) low-cut fi=
lter. Implementing such an adjustable filter by software that is running on=
 the digital signal processor (DSP) of the recorder should reduce the produ=
ction costs. So, it would make sense to do it that way.

Regards,
Raimund







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