Voice signal amplifying and filtering circuit

The invention provides a voice signal amplifying and filtering circuit. An audio input signal is amplified by about 16 times through a common emitter amplifying circuit composed of an R1, a resistor R2, an NPN triode Q1, a capacitor C6 and a resistor R4. The amplified signal is blocked by the electrolytic capacitor C2 and is coupled to a next-stage collector amplifying circuit consisting of a resistor R3, an NPN triode Q2, a capacitor C7, a resistor R5, a capacitor C7 and a resistor R9 to be further amplified by about 10 times ; the audio signal is coupled to the secondary through a transformer TR1 with the homemade turn ratio is 23: 48; high-frequency clutters of signals are filtered out through a capacitor C9 and a capacitor C8 and then coupled to a forward input end pin 3 of the integrated operational amplifier U1 through an electrolytic capacitor C3, and audio signals are output from an audio signal output port after being amplified through the integrated operational amplifier U1and subjected to blocking