[sdiy] Variable waveform LFO

[Tim Parkhurst]

On 1/12/07, Mike <profpep at hotmail.com> wrote:
> >.  This helped when I was working on SNIC circuits.
> >
> > http://home.earthlink.net/~ijfritz/sy_cir10.htm
> >
> Looking at this, I vaguely remember a circuit for a variable waveform
> oscillator from years ago, working on a function generator principle. It
> depended upon a switchable current mirror, (I think), in the charging
> circuit. This allowed the main waveforms to be varied from a positive decay
> sawtooth via a triangle  to a negative decay sawtooth, on one output, and
> from about a 5% to a 95% mark-space squarewave on the other. I'm sure it's
> around somewhere, but I've not seen it recently. I'm not sure if it was
> stable enought for a main VCO, but it made an interesting and useful LFO.
>
> Any suggestions, or is my google-fu not good enough?
>
> ||\/||ike
>

If you're looking for an LFO with a manually adjustable variable
waveform, then Ray Wilson's "Cool New LFO" will do the trick:
http://www.musicfromouterspace.com/analogsynth/coolnewlfo.html

The VCO from the PAiA Gnome uses the same trick (but the waveform is
still manually adjusted). If you want a variable waveform under
voltage control, then you've got your work cut out for you.


Tim ("Google-fu": I like it) Servo
-- 
"Imagination is more important than knowledge." - Albert Einstein