[sdiy] How to make a continuously variable wave LFO or VCO

[Harry Bissell Jr]

That sounded good... but the simulation I just did
of the waveshaper shows it pans from sawtooth to
mixed sawtooth / pulse to PWM (including square)

I didn't get any triangle wave out of it... can any
owners confirm if it does indeed do a triangle ?

H^) harry

--- Michael Bacich <weareas1 at earthlink.net> wrote:

> 
> On Sep 26, 2006, at 11:09 PM, Dave Manley wrote:
> 
> > The circuit is similar to what Paul describes.
> 
> Well, yes and no.  The Micromoog's octave doubler
> circuit has a  
> center-tapped pot as Paul described, but it pans
> only between two  
> suboctave square wave outputs (full CW and full CCW)
> and the main VCO  
> wave (in the center of the pot).  That's R435 in the
> drawing -- it  
> has a label that says "DOUBLING".  However, that's
> not the  
> continuously variable waveshape control that is so
> unique on the  
> Micromoog (and Multimoog).  The actual waveshape
> knob is R414 (a few  
> inches to the left of the other pot), and it's
> labeled "WAVESHAPE".   
> As you can see, it's a voltage controlled
> waveshaping circuit, and  
> turning the pot changes the wave from Triangle, to
> Saw, to Square, to  
> Narrow Pulse (or maybe it was Saw to Triangle to
> Square and Pulse?  I  
> can't tell from looking at the circuit).  It's kind
> of like a super  
> voltage controlled Pulse Width Modulation circuit. 
> You'll note that  
> modulation sources (such as LFO, etc.) are also
> applied to the  
> waveshaper via R416.  It's a way clever circuit, and
> as anyone who  
> owns a Micro will tell you, it's very fun and
> musical to use.  I'm  
> surprised that we don't see this kind of thing more
> often in VCOs.
>