[Milsurplus] SIMPLE Carbon Microphone Substitute.

[Hubert Miller]

What threw me is, the electret mic as a two terminal device is not actually
a source follower.  The gate is returned to the source,
not the FET's signal ground. At least per the schematic
https://en.wikipedia.org/wiki/Electret_microphone#/media/File:Electret_conde
nser_microphone_schematic.png

It's a two terminal variable resistance. 
I hadn't realized this feature of the many electrets i've harvested. 
What will remain a puzzlement for me, is why, as Dave reported, his electret
is entirely polarity dependent.
The FET should be able to be polarity "rolled", and the electret element is
permanently polarized, a DC nonconducting device.
-Hue