grins:
Thank you for the detailed reply, but Im not sure what you mean. My understanding is that plugging a mic into the input of an amp or "amplifier" and a headset into the output wouldnt work as the mic requires a preamp. It is quite possible that I may be mistaken here and would appreciate any clarification.
Let me clarify: you need an amplifier with a microphone input. Some only take a 'line in' input but there are plenty that will take a microphone input. Since you're only expecting to drive headphones you only need a very low power amplifier. I wouldn't expect any problem finding a low cost commercial amplifier to do the job, and it would be a relatively simple electronic project to make your own if you preferred the DIY route. Either way I'd be looking for an analogue solution, no need for a digital microcontroller here.