Serge Waveshaper schemos on Music Machines

Dan Higdon hdan at
Fri Jul 17 00:28:16 CEST 1998

From: Jim Johnson <jamos at>
>1) Which waveshaper is it? It looks closest to #2 based on the number of
>ins and outs, but it's not a perfect match.

I don't know - I haven't breadboarded this one yet, either.  The LM3900
is a quad, so I'd guess it's the other waveshaper - the one with multiple
identical sections (dang - I don't have my Serge catalog handy).  Maybe
a VC wave->square converter?

>2) Anyone know which input is which?


>3) What's the polarity of the op-amp - which terminal is +?

3rd strike - but I'm not quite out yet.  :-)

>4) Why use an LM3900 in this circuit, rather than a TL-074? 

That one I *do* know - the LM3900 is a "Norton Amplifier", and as
such has some magical properties.  :-)  Seriously, the circuit only
works *because* it's an LM3900.  Mr. Serge patented a couple
of designs based on this chip.  If you look at the data sheet for it,
you'll also notice the Serge VC pulse divider.

hdan at
"Trust not the monkey, nor his clever schemes" - hdan

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