I have three D104 mics wired up for different rigs. On the SDR-1000
into a Delta 44 sound card I use the built in preamp in the mic base to
get enough audio to drive the line-in input. This minimizes the RF
pickup through the audio wiring.
For the Drake 4 series I run straight into the mic input. Same for the
TR-7. My guess is the TR-7 doesn't sound as good as the 4 stuff because
of the lower input Z. But then again I don't listen to myself either.
And I usually run a 7077 mic on the TR-7 which is a dynamic.
On the O'scope a good "Hooie-yah" gives 200 mv P-P from each of the
elements. Thats 0.2 volts using a 10X probe on the scope input. You
can do the same test with a digital voltmeter too. Then you should see
70 mv RMS if my math is good today. Needs to be a 10 meg input meter,
an old Simpson will give a lower reading.
Google the D104 or Astatic and you can find a bunch of good info on the
care and feeding of the crystal elements. One site had a comment
attributed to an Astatic engineer who said that the preamp was necessary
to get the mic sounding good because of impedance matching. Just turn
the preamp gain down a bit
73, Larry K2LT
drakerepair.com
I know this is a dumb question, but are you sure the D-104 is of the
High Z variety?
Not dumb at all. How can I tell? It puts out about 10mv ptp into a
scope. Did not measure the DC resistance because I am not sure I can
apply voltage to it safely.
js
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