[sdiy] Littleman Wave Shaper (+ resonance pot tip)

[Theo]

I'll give it a try.
At first sight it looks like a shaper for "spaced" saw waves.
a uncommon, but quite usable wave form.
The positive part of the input waveform is cut off,
and the negative part is let through.
However the 22k to 120k ratio on the second opamp seems a bit steep
and suggest the wave form is hard clipped to from a pulse wave.

If it is to give a pulse output a more conventional "comparator" setup may
give better results than this circuit, and use less parts.

An other thing I noticed is the Resonance pot in the VCF (where else).
You may wish to replace the 10k pot with a linear 100k pot and
a 10k resistor from the input/top of the pot to the whiper.
This will result in a "reverse" log response of the resonance control.
Note this trick only works here because:
1) the pot is used as a voltage divider.
2) there is no loading on the whiper, as the opamp has a high impedance
input.


Theo




From: Jimmy Gogas <toothpick_77 at hotmail.com>

> I was looking at the Littleman Wave Shaper circuit, and I couldn't quite
> understand what kind of waves it was trying to output, so I decided to
> simulate it with a sawtooth input. The output waves (they slightly change
> using the potentiometer) are pretty "messed up". I don't really understand
> why someone would want to use these waves (or mix them with the sawtooth
> output of the VCO). Can someone explain me why?
>
> The circuits can be seen here:
> www.itn.liu.se/~nikro/littleman/littleman.pdf
>
>
>
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