Posted on Jan 14, 2013 10799
The 10k resistor is used to adjust the sensibility if the electret microphone, the 100k resistor is used to adjust the volume. In theory, this circuit will not work because it needs a pre-amplifier. Supposedly, a 741 or any othe pre-amplifier is needed. As I said before, I don't follow the theory. I already verified that the pre-amplifier is not needed, just adjust the 10k variable resistor. In fact, You may not be able to get the circuit to work properly with a pre-amplifier. Warning: May be too loud The 220uF capacitor can be replaced by any other if that value is not available. Do not connect the speaker directly to the output pin. If you are using a tweeter (or piezoelectric) you can connect it directly. 7/9/2006 - UPDATE: This schematic can be used for almost ANY application that needs an amplifier. The switch labeled "Boost" activates the gain of 200 if the input signal is too weak.