[Milsurplus] Carbon Mic Subs

[Dave Maples]

All: I finally had some time to look further into this.  I looked at the
ARC-5 modulator, and the one for the ART-13.

The ART-13 was designed for a carbon mike with an internal resistance of
approximately 40 ohms resistance.  With that resistance, the mike draws
about 77 ma through the modulator circuitry.  Full modulation at full power
on the ART-13 can be delivered with a mike output of 1.65 volts (RMS, I
presume) at 1000 Hz.

A single transistor is going to require something on the order of 750
microamps bias to drive the collector to draw 75 ma (assuming a beta of
100).  It's not clear to me that a single-transistor circuit would provide
enough drive from any kind of mike-level signal.

A Darlington pair, on the other hand, ought to be able to drive the socks
off the carbon mike input.

I'm now fiddling around with a two-transistor design.  Riddle me this: What
kind of mike would folks like to see?  Low-Z dynamic?  High-Z dynamic?
D-104?

Thanks,
Dave WB4FUR