Figure 25. Remote microphone with amplifier.
Transistor VT1 type KT361, the base through which the capacitor C2 receives the signal from the microphone M1, together with the resistors R2-R4 forms a single-stage microphone amplifier. The VT2 transistor KT315 type is an emitter follower and the function of dynamic load of the first stage. The current consumption of the microphone amplifier does not exceed 0.4-0.5 mA, so it can be powered from a power source of the amplifier of sound frequency. The amplifier is operable in the range of supply voltage V. 3-9 Resistors devices are used such as MLT-0,125. The microphone M1 - any sectretly the microphone. Instead of transistors VT1 and VT2 can be used transistors type CT and KT3102, respectively. Configuring the audio frequency amplifier is to install by selecting the resistance of resistor R3 to a greater voltage output. Connecting the microphone with the main unit, shielded wire, but use ordinary wire or wire type "noodles". When using long connecting cable, a deterioration of the quality of the reproduction signal due to large interference on the wires.