AW: Serge Waveshaper was Re: Harmonics question

Haible Juergen Juergen.Haible at
Fri Jul 3 17:12:20 CEST 1998

>  SC> The second section is...well, no one really seems to know (prove me
> wrong,
>  SC> folks!). It seems to work as follows: When the signal voltage reaches
>  SC> certain thresholds (positive or negative), the signal "wraps around."
> Easy
>  SC> to do in digital (the Nord Modular implements it, and it sounds
> GREAT), but
>  SC> I don't know how to do it in analog. 
I was going thru this thread once more (sorry for the late reply), and then
made some experiments with my Interpolating Scanner (schemos and
full description finally on my page at Synthfool), set to waveshaping mode:

When I set every even breakpoint to maximum, and every odd breakpoint to
I can create a "zigzag" courve, i.e. a triangle waveform in the voltage
When I modulate this with a normal (time domain) triangle wave of increasing
amplitude, I get a result that *might* be close to the one you described:

The output starts with a triangle wave at fundamental frequency, and at some
the peaks are folded back to become ever increasing tringle shaped dents.
At some point, there is a triangle with higher frequency,
and soon after that the peaks of this wave are folded back, too. And so on
higher frequencies.
I do not know if this is what this famous Serge module does (can anybody
check this on a real Serge waveshaper?), but if that is the case, it's very
easy to clone, because we'd only need a fraction of the Interpolating
circuitry for that: Omit the VCAs, and omit every other channel completely
(triangle functions not overlapping anymore, but touching the neighbouring
one at its base). Speculating further, I bet Serge has build his module
3900's and not saturated pnps. Let me see, one 3900 for 4 triangles, so you
can imagine to what high number of maximum harmonics one can get with a
handful of these chips.

What do you think ?


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