To: | [email protected] |
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Subject: | Re: LF: Sound Card Impedance |
From: | "Johan H. Bodin" <[email protected]> |
Date: | Thu, 16 Dec 2010 13:26:54 +0100 |
In-reply-to: | <5BB571709EEB4C2084239E924B0EACEE@lindavideo> |
References: | <5BB571709EEB4C2084239E924B0EACEE@lindavideo> |
Reply-to: | [email protected] |
Sender: | [email protected] |
User-agent: | Mozilla/5.0 (Windows; U; Windows NT 5.1; sv-SE; rv:1.9.2.13) Gecko/20101207 Thunderbird/3.1.7 |
I measured the input impedance of the mic input on a Dell laptop: AC input impedance: 4.3 kOhms (-6dB with 4k3 resistor in series) Mic bias voltage: +3.8V (open circuit) Output current: 809uA (shorted to GND) This suggest that there is a 4k7 pull-up resistor to +3.8V for mic DC bias. It may vary somewhat between different brands and models of course but all soundcard mic inputs that I have seen so far puts out some DC bias for electret microphones. 73 Johan SM6LKM ---- Ken wrote: > Hello all. > Does anyone know the approximate impedance of the mic input jack on a pc > sound card. > > 73. > Ken > M0KHW |
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