3 replies to this topic

[Rybags]

PWM sound uses a duty cycle which averages out over the sample period to generate the same result as modulating a wave to a certain position.

Has anyone tried, or got any software which does it?

There is an article here http://www.ffd2.com/...c=hacking20.txt and here http://www.ffd2.com/...c=hacking21.txt about digitized sound on the C-64.

I've been playing about with it on the 130XE, using various techniques like POKEY timers, and have tried playing direct POKEY sound and forced volume (alternating 0 and 15).

So far, my results aren't so great. I'm using voice 1/2 combined on a 1.79 base, which allows Timer resolutions to a single machine cycle.

[DamageX]

you may be interested in this http://members.aol.com/MJMahon/

Mr. Mahon created a program to play 5-bit samples on an Apple IIe using PWM.

[UNIXcoffee928]

How are these experiments working out?

Signal Modultion can be quite useful in feedback-oriented control systems... (if you redirect that output for non-audio control...).


L8R,

UNIXcoffee928

[Rybags]

I got it to the point where it played recognisable samples, using 2 methods.

1st method was the classic "Volume only" output.

2nd method was using a voice pair at 1.78 MHz -plus using Pokey timer (which forces modulation cycle to restart).

Both results poor so far, plus you get the carrier frequency which can't easily be filtered.

I haven't touched it for some time - devoting programming time to Impossible Mission project.