Piezo discs have been around since the 1970s, and such cheap (and easy-to-handle) discs are widely used by avid electronic hobbyists and experimenting musicians all over the world. A piezo disk ...

This audio amplifier circuit is useful in classrooms to reduce the strain of lecturing ,if the surrounding environment is noisy. It uses the power amplifier IC LM380 that gives 2 watts output which is ...

IT is not absolutely necessary that the microphone should form part of the direct circuit. It works just as well if connected so that, when the carbons are not touching, the whole of the current goes ...