There was a very large variety of microphones which would work with
this transmitter, any high-impedance mic will do. There are still some
made but I am not current on what is available. Solid state stuff can used
low or medium impedance mics directly but old vacuum tube TX need a
matching transformer for them.
The main manufacturers of high impedance mics for public address or ham
radio use were Electro-Voice, Shure Brothers, Astatic, and Turner. In
addition American Microphone made a line but were a smaller company.
Crystal mics are vulnerable to heat, humidity, and mechanical shock so
old ones are often not working. Moving coil, so-called dyamic mics, are
very rugged and generally will work as well as when new if they have not
been damaged in some way. Crystal mics were popular because they had very
high output and were cheap. The D-104 was one of the first, if not
actually the first, crystal mic on the market and has remained popular
ever since. The early ones came with a choce of flat or rising frequency
response but the rising response version was so much more popular that the
flat version was discontinued. At least part of the sound is the result of
the fairly large baffle area of the case. This causes a diffraction effect
which increases the high-frequency output and makes the mic slightly
directional at speech frequencies, both desireable for communication
purposes.
I think its possible to get new elements for old D-104s but I would
check first, they may be expensive since the D-104 has become a
collector's item.

--
Richard Knoppow
Los Angeles
WB6KBL



D-104C had a "ceramic" crystal element which was far more tolerant of
moisture, shock, etc.
I can't remember just now what the frequency response was (compared to the
original) but when
I used one, I was looked down upon as a traitor to tradition.
What was good about the D-104 types, was that you didn't have to speak
directly into it. One
could just walk around the shack, and in some instances, around the house
with little loss of
readability.

Old Chief Lynn, W7LTQ