Darrel,

Thanks for the advice, never thought that the scope / soundcard software would cause that issue...

I've not given up entirely on using a PIC, as I feel they offer a lot more and simpler than using descrete components. I'll keep plugging away and see what I come up with.

I assume that using a 100 Hz frequency for the PWM would be ideal... what PIC did you use, and is having an internal clock an issue (I'm using a 12F675 for experimential use)