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From: whaley@uiuccsb.UUCP
Newsgroups: net.aviation
Subject: Re: Querry on headsets: using stereo or - (nf)
Message-ID: <2376@uiucdcs.UUCP>
Date: Fri, 8-Jul-83 23:35:28 EDT
Article-I.D.: uiucdcs.2376
Posted: Fri Jul  8 23:35:28 1983
Date-Received: Tue, 12-Jul-83 21:08:06 EDT
Lines: 20

#R:ut-ngp:-39700:uiuccsb:5900002:000:1152
uiuccsb!whaley    Jul  8 13:26:00 1983

Resistance of "real" or "expensive" headphones is often 600 ohms.  It is
possible to buy transformers to convert the audio to 8 ohms for regular
stereo phone for under 2 dollars if you know where to look.
What I have done is go into radio shack (a place I don't recommend,
as they usually sell very inferior stuff), and look at their
audio transformers.  They sold one at one time that converted 1000 ohms
center tapped to 8 ohms.  It was intended for push pull transistor
amplifier output coupling.  (If you don't understand that, don't worry.)
I used the center tap with one end connection, getting half the 1000
ohms, or 500 ohms.  That is close enough to 600.  8 ohms isn't close
enough and can damage the aircraft audio panel.  On a Grumman tiger
an 8 ohm earphone caused one radio to break into oscillation, while
the other was unaffected.  600 ohms is quite standard for some types
of application, and there are real 600 ohm to 4, 8, and 16 ohm
transformers.  The one I bought had the advantage of being small
and cheap; it was so small I taped it into the patch cable I had
made to go from the 1/4 inch phone plug to the 1/8 stereo phone plug.