Alarms & Security Related Schematics and
Tutorials
ECM Mic Preamp / Pre-Amplifier
Parts:
U1
LM741 op amp ic
R1
1 megohm resistor
R2, R3
6.8k ohm resistor
R4
1k ohm resistor
C1, C2
0.47uF ceramic capacitor
MIC1
electret condenser microphone
All resistors are 5 or 10 percent tolerance, 1/4-watt all capacitors are 10 percent tolerance, rated 35 volts or higher.
This circuit amplifies the output of a regular electret condenser microphone quite nicely.. adjust sensitivity by turning R1
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