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RE: how best to connect a hydrophone to a laptop?

Subject: RE: how best to connect a hydrophone to a laptop?
From: Cetacean Research Technology <>
Date: Thu, 08 Jan 2004 14:51:26 -0800
 >Btw, by connecting a hydrophone, which typically has an impedance
 >corresponding to 3 nanoFarad to a microphone preamplifier, which typically
 >has an input impedance of 10 kiloOhm, you get a low frequency cutoff
 >frequency at 1/(2 * PI * 3 nF * 10 kOhm) = 5 kHz. So you end up with a
 >frequencyresponse, which is flat from 5 kHz to 20 kHz, which is not quite
 >what you desired.
 The capacitance and output impedance of hydrophones can be quite variable.
 In addition, some hydrophones have integral preamplifiers, so transducer
 capacitance is not important in deciding on which digital interface to
 chose.  For example, the Cetacean Research C10 and C13 hydrophones do not
 have integral preamplifiers and their capacitance is ~9nF, which would
 result in a low frequency 3dB point of 1768Hz assuming a sound card input
 impedance of 10kOhm.  However, the C54XR and the C304 hydrophones have
 integral preamplifiers with an output impedance of 2.5Ohms.  These
 hydrophones will work with any interface unit without limiting the low
 frequency response.
 Joseph R. Olson
 Cetacean Research Technology
 PO Box 70186
 Seattle, WA  98107
 Tel/Fax: +1 206-297-1310
 <a  href=""; 
 Cetacean Research Technology
 a strategic partner of Sound Technology Inc.
 Spectra Group - Signal Analysis Division

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