tsunamy_boy:
Would you please be more specific about thisGrumpy_Mike:
You simply bias the audio signal to 2.5Vto generate the negative parts of the wave.
You have two 10K resistors in a potential divider going to each voltage rail. You connect the arduino input to the junction. You then feed in the audio through a capacitor. Like in the front end of the circuit shown here:-
http://interface.khm.de/index.php/labor/experimente/arduino-realtime-audio-processing/
by PC i meant usual computer microphone
That is not a microphone type!!!
You seem to know so little about what you are doing I suspect that this project is beyond you.
I have used an MCP4921 for the D/A it is a 12 bit converter.
You can run the internal arduino D/A fast if you do this:-
// set up fast ADC mode
ADCSRA = (ADCSRA & 0xf8) | 0x04; // set 16 times division
The sound quality is quite acceptable with this arrangement.