[sdiy] more on which VCO (low fi "electro" ones)

[Scott Gravenhorst]

If you look at VCOs that can track a CV, you'll find that they generally exist
in two flavors: triangle and sawtooth.  They track a CV because they have linear
ramps.  It is this fact that makes them musically useful.  An example of a
nonlinear VCO would be a multivibrator that uses a simple resistor to charge the
integrating cap.  Here, you have an exponential curve instead of a ramp and
while this will sound different from a ramp, it will not be musically useful in
that it won't track the CV linearly.  In less than an octave it will be "out of
tune" with a standard scale.

I think what you're after isn't really called "low-fi", rather you want is to
screw up the waveform so that it's no longer a ramp or a triangle.  But you also
want the sound's pitch to track a CV so that it's musically useful.  The way
this is done in the modular world is to use a good VCO into waveshapers and
filters.  Waveshapers come in many varieties and many members here have
schematics for all kinds of them posted.  Hardsynch is another method for
screwing up a waveform and maintaining musical usefulness and it sounds
interesting.  Pulses and squares are easy to make with comparators and they
sound characteristically buzzy.  Filters can then further contour the waveshape
to give you an infinite variety of different timbres.

I hope this was helpful.

Linium <intent at netpratique.fr> wrote:
>BTW,  speaking of VCO, i would be happy to know if some designs are known to 
>be peculiarly not clinical and not scientifcly accurate, but instead low-fi 
>and hopefully flavorish.
>
>My point is that it could amusing to have some VCO that sound buzzy or somehow 
>instable with a lot character. Even if they are usable on 2 otcaves, what the 
>problem if you have already a bunch of accurate VCO ? You just need something 
>different sometimes.
>
>I guess that the earlier designs with discrete parts could be interesting. 
>Does someone have some opinion and advices on some raw and low-fi VCO ?
>:)) Well, with some germanium diode/transistor or something like that ?  
>
>I hope not shocking everyone ! But after the messy workspace thread, i feel 
>authorized ;) 
>
>Linium
>
>  
>

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