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

[Dave Manley]

Hey, I was going to simulate it tonight.  Now what am I going to do?

I looked at the users manual last night and it didn't mention triangle 
as an option.  This article by Mark Vail confirms:

http://www.backstage-lounge.com/story.asp?sectioncode=66&storycode=5780

-Dave


Harry Bissell Jr wrote:
> 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.
>>
> 
> 
>