The audio section is fairly straight forward. One thing to be aware of though is if you plan on using a dynamic mike, you will have to add a blocking capacitor in the line to the mike. The easiest way to do that is to turn the board over and open the circuit trace with an exacto knife near the mike connector pin. Scrape the solder mask off and solder the capacitor so that it bridges the open you created. You can see the open just to the right of the left hand cap lead. If you forget to do this and connect a signal generator to the mike connector, the amplifier won't work as the generator output resistor effectively shorts out the transistor base bias. It's easy to forget to do this. I know. I've done it several times and didn't discover it until I was deep into the troubleshooting mode and measuring the base bias.
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