I'm getting ready to write a faq on this one, we answer it so often.

OK, here we go. It is not a simple impedance matching problem. It is more
like "how do I get my barbecue to paint the house" issue. The military
microphone is generally moving coil (dynamic) that puts out a few millivolts
at an impedance of somewhere between 20 and 50 ohms.

The civilian microphone uses several technologies (dynamic, electret, ribbon
....) to transduce the voice to an electrical signal, but whatever technology
is used it is always followed by an amplifier of some sort to force the
output to resemble a carbon granule microphone which "looks" like somewhere
in the vicinity of 600 ohms with an output of half a volt or so.

Somewhere in these groups a couple of months ago, there was a pointer to an
Aussie site with a single transistor very simple amplifier that was reported
to do the conversion well. I lost that pointer; can somebody else repost
that site please?

Jim


"Scott VanHoveln" wrote in message
...
I need to know how to make a headset converter that allows me to use my
military (low impedance mic, single plug) headset in a GA airplane. The
plug pinouts I can probably figure out, but the mic impedance matching has
me stumped. Thanks all.

-Scott