[sdiy] Serge Triple Waveshaper mods

[Harry Bissell Jr]

Can you tell me the voltages that you send to the
various inputs and the level of the sawtooth.
I remembered that I have a spice simulation set up for
this... I'd like to see if I can duplicate your
results.

Can you tell me how you adjusted the trimpot on the
output (for gain, offset, cool sound whatever ???)

1) The glitch you described IS the retrace of the
sawtooh.

2) The sinewave is probably because of the larger
cap you used... I think its more LPF than waveshaper.

Hey with a couplt of folks on this we might put the
waveshaper to bed once and for all.

I have some EFM versions of this, mebbe I will build
one.

H^) harry





--- Michael Ruberto <frankentron at hotmail.com> wrote:

> I used a 1uF decoupling cap. Maybe it caused the
> sine glitch???
> 
> M. A. Ruberto
> 
> 
> >From: Harry Bissell Jr <harrybissell at prodigy.net>
> >To: Michael Ruberto <frankentron at hotmail.com>,
> synth-diy at dropmix.xs4all.nl
> >Subject: Re: [sdiy] Serge Triple Waveshaper mods
> >Date: Fri, 2 Sep 2005 09:20:36 -0700 (PDT)
> >
> >Fascinating, Captain...
> >
> >Now I wonder why it says "no decoupling capacitor"
> >on the schematic. Is this because there ISN'T one
> >on the original, or because it will not work with
> >one.
> >
> >I would be very surprised to see 'no decoupling
> >capacitor' on such a design, but there are times
> when
> >you don't WANT to use one.  Some 'bent' CMOS
> circuits
> >acting as linear devices should NOT have decoupling
> >caps... and in those cases the schematic should SAY
> >that.
> >
> >Ken ???   Anyone ???
> >
> >H^) harry
> >
> >--- Michael Ruberto <frankentron at hotmail.com>
> wrote:
> >
> > > Hi all,
> > >
> > > I have been playing around with the fascinating
> > > triple waveshaper by Serge.
> > > I am using Ken Stone's schematic:
> > >
>
>http://www.cgs.synth.net/synth/serge/pic/schem_tri_wave.gif
> > >
> > > It's an interesting circuit and truly does
> convert
> > > saw waves to sine. I did
> > > find, however, that it does so with a big
> glitch,
> > > might this be because I am
> > > powering it from +/- 15V?
> > > I eliminated the glitch completely by replacing
> the
> > > 100pF cap with a 2200pF.
> > >
> > > While I found the circuit to operate properly I
> > > wasn't too excited by it's
> > > sound. Rather boring for my tastes. So of course
> I
> > > had to experiment...
> > > I managed to get a much more interesting sound
> by
> > > removing the diode in
> > > parrallel with the 2200pF cap (formerly the
> 100pF).
> > > Now the circuit will not
> > > only transform the saw to a sine but will
> continue
> > > on to a trapezoid and
> > > then square.
> > > This makes for a wider range of timbres over the
> CV
> > > sweep and really reduces
> > > the yawn factor.
> > >
> > > Also, reversing the polarity of the diode
> between
> > > the 2 inputs yields some
> > > rather different looking waves.
> > > I guess since I'm building 3 of them I'll have a
> > > normal one and 2
> > > differently modded ones.
> > >
> > > The LM3900 is suprisingly still available and
> easy
> > > to find. I bought mine at
> > > a local marine electronics store of all places
> but
> > > many places on the web
> > > are carrying it. Allied has it for 77 cents and
> > > their part # is 735-5442.
> > >
> > > If there are any more interesting mods for this
> > > circuit I would love to see
> > > them.
> > >
> > > M. A. Ruberto
> > >
> > >
> > >
> >
> 
> 
>