[sdiy] Pulse Width Modulation sampling??

[Alwyn Nixon-Lloyd]

hi, you might want to try
http://www.acid-play.com/download/Penguins_2000.php

it seems to explain the technique for the C64.

Alwyn

> > Hello everyone,
> > I read somewhere out there, about how people used to
> > use pulse width modulation to create sort of
> > samples/(audio redcordings?) for the commodore 64.
> >
> 	I think you are talking about mod files. These were something like a 4 channel sound source - probably done by the SID chip using PCM modulation (unless someone corrects me). Some of the best files I recall were public domain demos done on the amiga.
>
> 	I used to have a dos mod file player and the hardware interface was a homemade parallel port sound card. This was basically just an RC network from what I remember with a headphone socket on.
>
> 	The sounds were average as the sampling frequency was very low. I seem to remember also that only 4 voices/ notes at a time were used but the sound list could be huge.
>
> > Does anyone know more about this?  Is it possible,
> > using this technique to create audio samples that play
> > via analog oscillators?  and what exactly is the
> > difference between pulse width modulation and pulse
> > code modulation (as seen written on old casio's and
> > the like)
> >
> 	PCM is how modern DAC's work, streams of 1's and 0's are integrated to a DC level. PWM is generally a fixed frequency and the pulse width changes - you could integrate this to a dc level and by changing the mark space quickly generate audio, but then this is practically PCM.
>
> 	Try looking delta sigma modulators or class D audio amps.
> >
> >
> 	mark
>