Return-Path: Received: from mail.cruzio.com ([208.226.92.37]) by truman.olsusa.com (Post.Office MTA v3.5.1 release 219 ID# 0-52269U2500L250S0V35) with ESMTP id com for ; Sun, 6 Jun 1999 13:05:24 -0400 Received: from testelectronics.mail (sa-207-251-8-81.cruzio.com [207.251.8.81]) by mail.cruzio.com with SMTP id KAA21883 for ; Sun, 6 Jun 1999 10:08:07 -0700 (PDT) Received: from main [192.168.16.1] by testelectronics.mail [192.168.16.1] with SMTP (MDaemon.v2.5.rB.b2.32-R) for ; Sun, 06 Jun 99 10:00:50 -0700 Received: by localhost with Microsoft MAPI; Sun, 6 Jun 1999 10:00:50 -0700 Message-ID: <01BEB003.749F9B00.ed@testelectronics.com> From: Ed Armstrong Reply-To: "ed@testelectronics.com" To: "'lancair.list@olsusa.com'" Subject: Re: 8:600 ohm Impedence Matching Tranformer Date: Sun, 6 Jun 1999 10:00:48 -0700 Organization: Test Electronics X-Mailing-List: lancair.list@olsusa.com Mime-Version: 1.0 <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> >> I think It may be better and easier to simply connect the stereo speaker outputs directly to the Flight Com intercom inputs with an 8 Ohm resistor across each audio output to load down the stereo output properly. The 600 Ohm com input shouldn't matter as long as the driving impedance is at or below 600 Ohms. In this case it would be 8 Ohms. The problem with using an impedance matching transformer is that it is going to step up the voltage 75 times. I think this high voltage could blow your com input! You shouldn't need ground isolation, but if you do, you can put two non polarized 10uF electrolytic capacitors in series. If you don't know whether or not you need ground isolation, try it with the capacitors out, if it squeals or sounds bad, try putting the capacitors in. I put a schematic and parts list on the web: http://www.testelectronics.com/ftp/comload.gif Regards, Ed Armstrong Watsonville, CA. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> LML homepage: http://www.olsusa.com/Users/Mkaye/maillist.html