Rob,

I too have both attempted to make Roman Black technique work and to contact him, without success.

I believe the way to go is HPWM but only know you need a sophiscated analog filter to get decent fidelity.

An example of a 4th Order Butterworth Low Pass Filter can be seen here:

http://www.freescale.com/files/32bit...68EZ328PWM.pdf

As the math gets pretty hairy for active filter design, this package was recommend to me by an audio engineer:

http://www.schematica.com/filter_wiz_files/FWPRO.htm

He also recomended storing the audio file in LogPCM format into a Serial EEPROM (STTS4900) and using SPI to configure the HPWM registers.

I have some pieces of this puzzle, but have wide gaps in between.

My application is to generate a high quality ding-dong sound complete with the fade after the ding and the dong.

We have tried the low cost melody chips from Tiawan but the quality is not acceptable. ICD products are too expensive for this design.

Jay