Amplifying sound - the audio amplifier

A microphone and amplifier can be used outdoors to listen to the sound of birds, autos, train, and people.  by placing several microphone, many hundreds of feet away from a hunting shelter or blind , you could listen for game approaching from unobserved direction.

part list :
R1,R2 10Kohm,1,4 watt
R3 1K ohm
R4,R5, 100K ohm
R6 1M ohm potensiometer
C1,C3 1uF, 35 V
u1, TL084 opamp
M1 dinamic or electret microphone
S1, SPDT toggle switch
B1, 9V battery


The diagram shown illustrates a microphone pre-amplifier. this microphone pre-amplifier was designed for an electret microphone, and bias resistor R1 is used if you utilize an an electret microphone. if you choose a dynamic microphone, eliminate this resistor.