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N1NKM's D-104 preamp page

N1NKM's D-104 Preamp

(Created: 11/30/2005)

Schematic

This is a very simple preamp to match a D-104 mic to virtually any modern rig. the D-104 mic element has a very high impedance of nearly a megohm. Modern rigs mic inputs are usually only a few K ohms.

NOTE! The 240 ohm and 470 uf capacitor should NOT be omitted! The actual values are not that critical, anything from 100 ohms to 470, and 220 uf to 1,000 will work. These are to DECOUPLE the preamp from the power supply. I was having a problem of audio feedback which was coming back through the power supply lines! Adding this little circuit completely cured that problem.