an Audio Amplifier with PIC
(going on with some funny applications...)
Using a PIC24 or a dsPIC, grab analog input from a Microphone, convert it (22/44 Ksamples/sec) into numbers, scale for PWM and send them to a speaker!
Several types of PICs can be used: a 70MIPS device with remappable pins is best, but not needed.
Using a 140MHz device we set PWM at 35KHz and drive the 2 PWM outputs in order to achieve the "power": keeping in mind the average limit of 20mA per pin/200mA maximum total, in theory up to 10+10 pins could be used - and deliver 3W over a 8ohm speaker.
4+4 output would also be good. At a very basic level, 1+1 pins are a starting point for this demo.
Of course the signal coming from Microphone (or other source) can easily be scaled or filtered in code.
Have (more) fun!