The circuit below is the Microphone Amp and Audio Amp Stage that is used in many of my transceivers. It works and works well so why not use it. The annotation shows this was used in the shirt pocket transceiver; but is is also in the JABOM. Essentially the output of the microphone amplifier is bridged with the input of the audio amp stage. Not to worry as both are not turned on at the same time. At the in/out junction is also where I connect the 988 Hz pulsed tone coming from the Arduino after suitable RC filtering.

Build this first as then you can test two circuits at the same time. The LM386-3 delivers room filling volume. Another version of this amp has an LM386 in the output with an NE5534 driver--so that is another option. Still if you want to blow out your ear drums you can build the LM380 variant which was used in the KWM-4.

These are well proven circuits and feature plenty of "umph' in a small foot print. There are those who pan the LM386 --this is communications audio not high end digital audio for the audiophile. Get a grip!

By the way the Audio Amp and Microphone amp are a mix of leaded and SMD components. So there is a bit of a mix and match in terms of the parts used.

The first circuit will be shown later with the add of the AGC circuit.







Audio Amp, Microphone Amp and S Meter Circuit Boards