A Serge Wave Multiplier Idea (Part 47)

[Sean Costello]

Hi everybody:

As I sit here, typing at my computer, working on the corporate web site,
listening to Harmonia and Klaus Schulze's "Irrlicht" (as well as the
inhuman yips of siamang monkeys - I live close to a zoo), my mind drifts
to the Serge Wave Multiplier, Module of Mystery.

Ok, so I ask about this damn module every few months.

This time, however, I have an idea.  I am pretty sure that the top
section of the module is something like an overdriven 3080 (differential
distortion).  The bottom section is probably four stages of an LM3900
cascaded together, where each stage is a voltage-controlled full wave
rectifier (adding voltage causes the module to morph from a voltage
follower to a full-wave rectifier).  

The middle section is a mystery. The best suggestion I have heard is
that it is a diode function generator, where different pairs of diodes
come into effect with louder signals (a VCA would need to be placed in
front of the circuit in order to add voltage control).  However, I
thought of a simpler solution last night: What if it is simply several
LM3900 voltage-controlled full-wave rectifier stages in series (as in
the bottom circuit), where each stage is followed by an op-amp inverter?
This would create foldover of the top and bottom of the waveform - each
stage would be creating foldover on a different side of the waveform.

The more I think about it, the more I suspect it isn't this simple. I
doubt that the above circuit would sweep through the odd harmonics
cleanly, as the Wave Multiplier is supposed to do with a triangle wave.
I think that it would work with 2 VC-FWR stages, but adding additional
stages would cause the circuit to depart from the behavior of the Serge
module. Intuitively, I think that the waveform would contain multiple
foldovers very quickly, instead of going from one triangle peak to 3 to
5 to 7 and so on.  However, the VC-FWR->inverting op amp->VC-FWR would
probably be a cool effect.

Any ideas, folks?

Sean Costello

P.S.  Just want to say again what a great list this is. You wouldn't
believe the flame wars going on over in Analogue Heaven right now. At
least people on this list are debating things like circuits and the
right way to offer advice and criticism, instead of some @#$%! bragging
about ripping off UPS on a COD delivery and getting bent out of shape
when people inform him that stealing is not a good thing to do.

P.P.S. Has anyone ever synthesized the sounds of a lemur?  Hearing two
lemurs talking to each other in close proximity gives you a better
understanding of beat frequencies.  Ring modulation that takes place
inside your head.  Man, I love heterodyning.