The Southgate Amateur Radio Club - the amateur radio site for all radio hams  
www.southgatearc.org
 

 

Mic Preamp

The microphone below I made and have used now for around 15 years. It has lots of gain and a very small current drain, the 1.5V battery will last for over a year with daily use.

Pre-Amp Microphone

Parts List
Resistors:
R1,R4 1K
R2,R7 100K
R3 470ohm
R5 10K
R6 510ohm
RV1 5K lin pot
Capacitors:
C1,C4,C7 1mf mini electrolitic capacitor
C2 1nf disc capacitor
C3,C5,C6 4.7nf disc capacitor
Transistors:
T1 BC549C
T2 BC559C
Other components:
E1 Electret Mic Element
SW1 D.P.D.T. Switch

 

MATRIX BOARD LAYOUT

 

DIAGRAM VIEWED FROM COMPONANT SIDE, COPPER STRIP ON OPPOSITE SIDE