C.Anderton's Pulse Width Multiplier

[Martin Czech]

SNIP
> " This construction project turns a static triangle waveform into a highly
> animated variation of a pulse waveform. ....... The PW multiplier uses four
> comparators, three of which have voltage controlable thresholds, to turn a
> triangle wave into a number of pulse waves with varying duty cycles.  These
> pulse waves are then mixed together digitally via EX-OR gate, resulting in
> a very complex composite wavform."
SNIP

Hmmm, this weekend a sat inside the house (damn weather) when I had a quite
similar idea:
Quantize  an input signal by an DIY comparator array, say
16 comparators 311 evenly spaced, with some logic (thermometer coding),
so that the input is
divided into 16 evenly spaced voltage windows. Each comparator
window belongs to an analogue switch, which activates a pot or control
voltage to the output. By proper setup, a saw wave will result in an
staircase pattern etc. This is getting towards an arbitrary wave generator.


Further on : each of the windows could be controlable, one could use
two mixed input signal instead of one etc. etc.
One could even do freqency multiplication, with no pll lag, though the 
accuracy will get down at the high frequencys due to comparator slew rate,
I think. E.G.: multiplication by 7 is possible by scaling the input, so that only
14 comparators are used, the odd ones with -1V output, the even with +1V
output.

Could be a very inexpensive circuit. But how does it sound?

I had no 311 available, nor the rest of circuitry.

Well, I can draw waves for my microwave with the mouse. 
I drew some "staircase" patterns,
and also patterns which emphasize some higher partial.
(The microwave is quite usefull for such quick tests and simulations.
I also can compute waves using some homemade algorithm.
A lot faster than soldering.)

Interesting sounds, some are WAVEish, digital, some sound PWMish ,Phaserish,
some exibit very strong partials one could possibly never obtain with a vc filter.


Much sound for a few bucks.

m.c.