Power megaphone circuit

Posted on Feb 5, 2014

Just about any power transistor can be used in this megaphone. Its suitable for boats, playing fields etc. the transistors Q1 & Q2 are the HEP-230 type which are easily available in the market. The transistors are parallely connected to handle the required power and speaker matching. The microphone is a carbon type like that used in telephone hand sets

Power megaphone circuit
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. If a regular carbon mike is used the push-to-talk (PTT) switch can be connected in place of S1 to provide PTT operation. There will be no warm up or capacitor charge time. Hi Rex HEP 230 is a PNP power transistor similar to AD149 or 2SB337. As the transistor is pnp collector should get connected to negative and emitter to positive. Mic should be carbon type only. To start with keep R1 at maximum value and by talking into mic slowly adjust the pot till god quality (un distorted)sound is heard with good volume. by adjusting R1 further will increase the current consumption and reduce the volume also. Never try with a car battery you may blow the transistors instantly in to smoke.

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