s3n4te:
If I add active low pass filter would that cause my output wave to be triangular?
Not for frequencies below the cutoff design frequency of the filter. Not sure how you are processing audio information via PWM output. Is this using some kind of PCM signal? Or are you just ramping up and down the PWM duty cycle using a audio sine wave table?
It's hard to design an effective filter unless one knows the signal format being used.
Lefty