Cross Product Sub Octave Module

[Ken Stone]

I've got a similar project presented here:
http://kato.sai.com.au/catgirl/synth/modules/subosc.html
This one uses a 4030 or 4070 exor gate, though of course with the CMOS
gates having similar pinouts, an AND or OR gate etc could easilly be
dropped into the same circuit. Personally, I found careful mixing of the
cross product and incoming signals could achieve the same affect as
using an AND gate, so I stuck with the EXORs.

Ken


Romeo Fahl wrote:
> 
> I didn't catch the original message, so I don't know what circuit is being
> discussed, but it reminded me of one of my "still-born" modules that is in a
> box in the basement:
> 
> A few years ago I built a slightly modernized version of Lester Ludwig's
> Sub-Octave Cross-Product Module. It takes two VCO inputs both of which go
> through their own comparator, then are fed  through a pulse divider, the two
> divider outputs through a set of AND gates.  The comparators' outputs, the
> dividers' outputs and the AND gates' outputs are fed into individual pots
> for mixing, then summed into an output opamp.
> 
> The original version used SN74161s for the dividers and I believe a 7408 for
> the AND gates, my version used a CD 4520 for the dividing and a CD4081 for
> the ANDing.
> 
> I think something got lost in the update, because the module worked for a
> while, then quit and I was unable to get it working again.  I posted the
> schematic here:
> 
> http://www.spiritone.com/~8brain/xproductflat.gif
> 
> If anyone can see any obvious flaws, please let me know.  It could be
> something simple in the connection between the opamps and the CMOS that I
> left out... just wasn't sure what would work best.  Or it could be my fuzzy
> slippers on the shag carpet were frying the CMOS (-*,
> 
> When it did work, it sounded like a ring modulator from hell... or a casio
> having a nuclear meltdown, depending on how the pots were set.
> 
> There's a good amount of room for modifications, like switching the divider
> outputs to different AND gates.  The 4520 also has reset inputs that can be
> pinged for extra nuttiness.
> 
> ----- Original Message -----
> From: "Sean Costello" <sean at staccatosys.com>
> To: <efm at xavax.com>
> Sent: Friday, October 20, 2000 2:22 PM
> Subject: RE: [EFM] mmb - lives!
> 
> >
> >
> > > From: Harry Bissell [mailto:harrybissell at prodigy.net]
> >
> > > Use the 4520 dual binary up counter... 2 - 4 stage counters
> > > in one chip. Smaller
> > > better...
> >
> > Good idea. Price is around $.45 at Jameco.
> >
> > > If you want ring mod, you need exclusive-or gates not  and
> > > gates.  OTOH
> > > and gates would sound cool also.
> >
> > Apparently AND gates sound far more "consonant" for dissonant intervals.
> The
> > nice thing about this effect is that completely noisy signals as inputs
> will
> > turn into fairly smooth square waves after being divided down by 16. Of
> > course, an XOR gate could be swapped in, if it had the same pinout.
> >
> > I was thinking that this configuration could be made even more powerful,
> by
> > incorporating a 3rd VCO that is divided down, and the results ANDed with
> the
> > outputs of the previous AND gate. This would multiply the suboctaves of
> all
> > three VCOs together, giving a sound that would be exceedingly superhuge.
> > Could be done with 3 4024 chips, 2 4081 AND gates, and enough resistors
> and
> > opamp stages to sum the outputs together as required.  Or, you could use 1
> > 4520 and a 4024, or use 2 4520 chips and have provisions for 4 inputs,
> or...
> >
> > Some other fun things I have done with this circuit:
> >
> > - Run noise through a filter, and use this as one of the inputs. The
> result
> > is very dense noise, but with some sense of pitch; as the Q of the filter
> is
> > increased, the output sound gains a much greater sense of pitch.
> >
> > - Use two or more signals as the input to one of the octave divider
> chains.
> > The result is nice and chaotic.
> >
> > I have also found that mixing in the straight, non-ANDed suboctave signals
> > greatly adds to the sound, so this should definitely be an option. Some
> > experimentation would be useful to determine the best way of combining the
> > outputs while using the minimum number of controls.
> >
> > I will put an MPEG on my website of these sounds in the next few days. The
> > sounds were taken from a digital algorithm, but should sound about the
> same
> > in analog (well, even better, as those square waves tend to alias in a
> > digital system).
> >
> > Sean Costello

-- 
_____________________________________________________________

                Ken Stone  sasami at blaze.net.au
                   ** Catgirl Paradise **
               <http://www.anime.net/~kens/>
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