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3 pronged mike

L

Little Monster

Jan 1, 1970
0
Hello all,

I got a second hand microphone the other day for recording interesting
sounds on a little piano-key type mono tape recorder.

The mike is made by Grundig, model GDM 311 seems very well made, and looks
like the sort your parents/grandparents might have used to record baby's
words on the family reel to reel.

It has screen + 3 wires terminated in a 3 pin DIN plug, these are the
outputs from some kind of matching transformer (I had a look) a low
impedance side which seems to match the recorders input, and a higher
impedance side. (I could only measure the DC resistance though)

So what I would like to know is, why the 3 wire arrangement? Is to
provide an alternative match for a non standard input, or is it to provide
some kind of offset earth connection - I'm guessing to feed a differential
input.

Any suggestions, anybody? It would be nice to know even if I'm not going
to use the extra wire.

Tia, Monster
 
A

Arthur Jernberg

Jan 1, 1970
0
Agreed, the actual voice coil is connected to 2 of the pins and the ground
is the third. Many Microphone designs used this inclusive of Shure. Been too
many years for me to remember the configuration tho.
 
L

Little Monster

Jan 1, 1970
0
Agreed, the actual voice coil is connected to 2 of the pins and the ground
is the third. Many Microphone designs used this inclusive of Shure. Been too
many years for me to remember the configuration tho.

So, without removing the shield to have a look, could this be an
auto-transformer sitting in there?

Monster
 
H

Harry Conover

Jan 1, 1970
0
Little Monster said:
So, without removing the shield to have a look, could this be an
auto-transformer sitting in there?

Monster

Given that most of the older Shure mics had a switch to select output
impedance, yes.

Harry C.
 
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