The D-104 Microphone W1CKI
Here is a neat way to make your D-104 sound like a $300 mic…or maybe better if you are running a old boat anchor.
This circuit was shown to me by K1DEU and is used by many AM’ers. It is an impedance changing circuit and allows the D-104 to see a high impedance, R1 25Meg. The output of the NJFET is low impedance . Very little gain is developed with this circuit.
Note the 270k input resistor R5 in the grid of the existing pre-amp. The mike input of a 12AU7 connected to the JFET output will only need about a 270K resistor for the grid resistor.
R7 and R2 can be used to "EQ" the audio, giving up to 6db bass or treble cut.
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