[Pd] Pd to CV for a Moog (OT)

[Chuckk Hubbard]

On 9/11/06, Damian Stewart <damian at frey.co.nz> wrote:

> you know the way a Mac laptop power light kind of 'snores' when it's in
> sleep mode? normally to make a light fade in and out like this you adjust
> the voltage up and down. but since you only have two possible voltages on a
> digital device - on (+5V or +12V or something) and off (0V) - you have to
> create the inbetween voltages by flicking on for a portion of time then off
> for a portion of time. to generate a +5V signal on a +5V digital output,
> turn it on all the time. to generate a 0V signal, turn it off all the time.
> to generate +2.5V, turn it on for 10 microseconds, then off for 10
> microseconds, repeatedly - and then low-pass filter the output (using a
> capacitor and a resistor). to generate +1.25V, turn it on for 5
> microseconds, then off for 15 microseconds, repeatedly, and low-pass filter
> the output - you get the idea, hopefully.
>
> this is how the snoring power light works - the light is actually flicking
> on and off thousands of times a second but your eye acts as a low-pass
> filter and mixes them all together into a continuous glow... and
> theoretically you can do the same thing to get a control voltage for your Moog.

This is awesome.  I get it now.  Though I'm not familiar with the
sleep light on Mac laptops, unfortunately.  Would it be any harder to
use the DAC output, converting the voltage from that?  It has a
low-pass filter, albeit one I can't control.  But then I don't have to
look up all those serial port connection diagrams.  I have to write
music some time during all this!

> > I don't know exactly how a Moog's PWM works, but from
> > his description I thought I might just as well generate sine, ramp,
> > square, triangle and pulse waves in Pd and run them through the
> > filters and envelopes on the synth.  And where's the fun in that?  But
> > if no other possibilities work out, I can use that.
>
> Since it's largely the filtering characteristics (and the hum, and the
> noise) that make analog gear sound 'analog', that's not actually such a bad
> idea.

It's sounding better and better.  I like the idea of being able to use
the FM possibilities of the oscillators, though, and I actually think
the guy teaching me the Moog might be offended if I suggest using
digital synthesis, lol.

Thanks.
-Chuckk