Serge Waveshapers

[Dan Higdon]

> From: 	jupiter4[SMTP:jupiter4 at bt-sys.bt.co.uk]
> 
> The waveshaper looks to be a simple circuit, but non of the inputs are labelled. Is the 25K log pot input the 
> Voltage control and the other 2 signal inputs?

It looks to me to be the other way around (attenuated input, 2 CV's and a dedicated parameter
knob).  I'm no expert, but it looks like this is a sort of variable sine shaper.  Probably, the
input signal is pushed towards a sin wave, with VC of both "halves" of the wave.  The parameter
knob allows manual control over at least 1 side of the wave.  I could be way off on the
"side" thing, it may just be a CV and inverting effect CV.

How do I get this?
1  If you do the math, you'll see that the parameter knob delivers roughly the same
   range of currents as the "standard" CV would through the lower input.

2  The CV inputs are negative guarded by diodes, and the audio is AC coupled.

3  The "trim" and general diode layout reminded me of a tri->sin converter, sort of.

4  The IC used is a quad model, and Serge still sells a "waveshaper" that does saw->sin.
   It is a triple unit with a "mixer" mode (hmm sounds like 4 opamps to me!).

Believe it or not, #4 didn't occur to me until much after I'd read the circuit.  You think
I would have memorized that catalog by now!  (Gotta save those pennies)

hdan