[sdiy] filtering cv

[Scott Stites]

Cynthia Webster wrote (about adding an AC/DC coupling switch:

"Try adding this very same feature to the inputs of a ring modulator -
Very Handy!"

Absolutely right on, Cynthia!  Ring modulators (four quadrant multipliers) are a great way to process CV's, if they're DC coupled.  For example, if you put in a sawtooth LFO to one input, and a slower sine or triangle LFO to the other input, the output will be a sawtooth that starts out noninverted, reduces in amplitude to 0V, then increases in amplitude again, only inverted, at the rate of the sine or triangle LFO.  Think of an automated Buzz-Click Gizmotron, and you get the picture.  Of course, that's only one application.

In fact, in the past few months, I've finished three modules for the KS-01 - a quad Log/Lin VCA of Ray Wilson's design, a quad LFO of Ray Wilson's design, using Thomas Henry sine shapers for the sine outputs (mainly to save my precious hoard of LM13700's), and a module I call 'Mixer Model 3', which is just my third in a design of multi-functional mixer modules.  This particular module has two four channel mixers, a 'Peak and Trough' function taken directly from Ken Stone's fabulous 'Analog Logic' design (modified so that the mixer controls of one of the mixers control the level of the signals applied to the peak and trough), and a four quadrant multiplier (ring modulator), plus some other stuff.   I put the multiplier in this module so that it can be used to process CV's or audio, and it's handy as heck.

I haven't updated the 'Birth of a Synth' page for all of this stuff yet - I've got so many irons in the fire, I don't know if I'm coming or going.  And that's the way I like it!

Cheers,
Scott




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