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

[Gene Stopp]

Nope, no triangles on a Multimoog. You want dull overtones ya gotta use the VCF to quiet things down.

I brought mine to the workbench for the bass boost mod recently and set it up afterwards to mess with it. Let me reiterate everybody what a vastly underrated machine this is (Multimoog, not Micromoog)!!! I tweaked up all the trimpots and let me tell you boys you can get a huge range of different sounds in a flash. Want VCO's at a fifth? Slam the detune to the right. Want VCO's at a forth? Slam detune to the left. Want perfect unison? Put detune at 12 o'clock (there's a trimmer to make 12 o'clock perfect unison). A little slop makes the perfect amount of beating. Then sub-octs for the 3-VCO sound if you want. Aftertouch on pitch and you can do wholestep bends with vibrato if you wiggle your finger. It's almost as fast as presets but you're doing all the work, and a lot more organic. Really makes your patch-brain work full steam, which somehow translates to better solos. Especially through a space echo... I'm going to a jam on Saturday and by golly I'm taking this thing along.


- Gene



-----Original Message-----
From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Harry Bissell Jr
Sent: Wednesday, September 27, 2006 1:24 PM
To: Michael Bacich; synth diy
Subject: Re: [sdiy] How to make a continuously variable wave LFO or VCO


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.
>