Return-Path: Received: from mtain-de05.r1000.mx.aol.com (mtain-de05.r1000.mx.aol.com [172.29.64.205]) by air-md10.mail.aol.com (v129.4) with ESMTP id MAILINMD102-8b994d0a10b437a; Thu, 16 Dec 2010 08:14:28 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-de05.r1000.mx.aol.com (Internet Inbound) with ESMTP id BA60A38000094; Thu, 16 Dec 2010 08:14:26 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PTDe1-00053C-Vy for rs_out_1@blacksheep.org; Thu, 16 Dec 2010 13:13:17 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PTDe1-000533-JT for rsgb_lf_group@blacksheep.org; Thu, 16 Dec 2010 13:13:17 +0000 Received: from cavuit01.kulnet.kuleuven.be ([134.58.240.43]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1PTDdz-0004rD-0m for rsgb_lf_group@blacksheep.org; Thu, 16 Dec 2010 13:13:17 +0000 Received: from smtps01.kuleuven.be (smtpshost01.kulnet.kuleuven.be [134.58.240.74]) by cavuit01.kulnet.kuleuven.be (Postfix) with ESMTP id 09D517B8056 for ; Thu, 16 Dec 2010 14:13:04 +0100 (CET) Received: from ICTS-S-HUB-N1.luna.kuleuven.be (icts-s-hub-n1.luna.kuleuven.be [10.112.9.11]) by smtps01.kuleuven.be (Postfix) with ESMTP id E06FE31E702 for ; Thu, 16 Dec 2010 14:13:03 +0100 (CET) Received: from ICTS-S-EXC2-CA.luna.kuleuven.be ([10.112.11.13]) by ICTS-S-HUB-N1.luna.kuleuven.be ([10.112.9.11]) with mapi; Thu, 16 Dec 2010 14:13:04 +0100 X-Kuleuven: This mail passed the K.U.Leuven mailcluster From: Rik Strobbe To: "rsgb_lf_group@blacksheep.org" Date: Thu, 16 Dec 2010 14:13:03 +0100 Thread-Topic: LF: Sound Card Impedance Thread-Index: AcudIOZTQQuewSBEQI2hRyAlCAAnvAAAVQj8 Message-ID: References: <5BB571709EEB4C2084239E924B0EACEE@lindavideo>,<4D0A058E.4010103@telia.com> In-Reply-To: <4D0A058E.4010103@telia.com> Accept-Language: nl-NL, nl-BE Content-Language: nl-BE X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: nl-NL, nl-BE MIME-Version: 1.0 X-KULeuven-Information: Katholieke Universiteit Leuven X-KULeuven-Scanned: Found to be clean X-KULeuven-Envelope-From: rik.strobbe@fys.kuleuven.be X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,none Subject: RE: LF: Sound Card Impedance Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=TO_ADDRESS_EQ_REAL autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false x-aol-global-disposition: G x-aol-sid: 3039ac1d40cd4d0a10b20301 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) Johan, at what frequency did you measure. I have measured a significant C (up to some nF) in parallel to R at the in= put of some soundcards. 73, Rik ON7YD - OR7T ________________________________________ Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.or= g] namens Johan H. Bodin [jh.bodin@telia.com] Verzonden: donderdag 16 december 2010 13:26 Aan: rsgb_lf_group@blacksheep.org Onderwerp: Re: LF: Sound Card Impedance 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 ele= ctret 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