There is a way to produce a wave that seems to me to be similar sounding to
PWM but actually using other VCO waves. I learned this trick from Ken
Elhardt. Essentially you use two waves from the same VCO. Wave # 1 is the
audio source and goes to a VCA. Wave # 2 is your shaping wave and is used
to control then gain of the VCA. Varying the gain of the control wave
shapes the audio wave at the output of the VCA. Use an LFO wave mixed into
to the VCA control with the audio wave so that you do not simply produce a
static, but re-shaped wave.
Here is some examples on the o-scope with sound. Sure it in not PWM. But,
close your eyes and listen to it and see if it has a PWM effect. To produce
this effect on an external monophonic signal, I would suppose one would need
a pitch to CV circuit to drive the VCO to be in sync with the incoming wave
and use the original signal into a VCA with the VCA as the CV. I am
thinking there might be some glitching while the pitch to CV found it's
mark. It might be interesting to try.
Anyhow, here are some little mpg files that shows this effect using the VCA
for waveshaping with the CV being controlled by the VCA itself and an LFO.
External audio timbre modulation really = 410 VCF :)
Larry
http://www.wiseguysynth.com/larry/misc/Mov01.mpghttp://www.wiseguysynth.com/larry/misc/Mov02.mpghttp://www.wiseguysynth.com/larry/misc/Mov03.mpg--------- original message
From: drg3orge <
doc@...>
h3y all,
is there a way to manipulate the duty cycle {for lack o' a better
term} of ∗any∗ audio signal??? CD, guitar, wife's flute, etc? was
thinkin' 'bout static waveforms an'timbre/pulse width modulation
while doin' the dishes an' had never considered the possibility about
tweakin' the duration of the 2 halves of a waveform.
does this make any sense? is it a stupid thought with no answer?
is it possible to achieve??
thanks,
doc