This circuit given here can be housed in the box containing the speaker to form a handy microphone amplifier.The device can be used by teachers,guides,lecturers etc for speaking in a crowdy or noisy environment.
The circuit is designed base on the audio power amplifier IC TDA 7052.The IC can deliver a maximum power output of 1.2 W at a 6V supply.The audio signal from the microphone is pre amplified by the amplifier based on Q1 (BC 547) and give to the input of IC1 (pin 2).The POTR5 acts as a volume control.The capacitor C3 is used to bye pass the upper frequencies in order to avoid the Larsen’s effect(the microphone picking up speaker output to cause howls).
Circuit diagram with Parts list.
- Use a 8 Ohm speaker or two 4 Ohm speakers in series as load.
- Assemble the circuit on a good quality PCB or common board.
- A 6V SMF battery is my choice for powering the circuit.
- Switch S1 can be used as a ON/OFF switch.