[sdiy] Fun things to do with a half SSM2164?

Jason Nanna jasonnanna at gmail.com
Mon Jun 14 00:54:22 CEST 2010

Hopefully it's not too late to throw in a comment but I would love to
see a VCA at the input jack as well!  Perhaps rather than having the
input jack mixed at IC3D, you could have the input amplitude become a
modulation destination.  I've been experimenting a little with using
the input as a separate feedback path for the filter.  A VCA at that
point might be helpful for that application.

Or even an input VCA that would bypass the filter altogether (for
amplitude-controlled mixing, post-filter).  The HPF seems great; I
think this would present some interesting opportunities as well.  I've
found little use for the audio input yet, It's nice to throw audio
through the filter but if it were more flexible as a loop or as an
input with its own amplitude control I think I would use it much, much
more.  At that point, though, it might be really beneficial to have a
loop send, loop return, and mix output (Then again, I think I'm at the
fringe with the way I configure my gear.)

And a question:  How are the unused analog outputs dealt with on the
firmware at the moment?  Are they implemented currently?


 On Sun, Jun 13, 2010 at 7:52 AM, Olivier Gillet <ol.gillet at gmail.com> wrote:
> Hi all,
> Thanks for the suggestions... I've just breadboarded a 1-pole HPF
> before the SSM2044 and it's working great (It only cost me an extra
> dual op-amp. Most of the other suggestions (modulating modulation
> amounts, ring-modulation are already done in software). The remaining
> cell will probably be used to modulate the cutoff frequency with a
> variable amount of the input audio.
> Pole-mixing would have been possible if the SSM2044 exposed a bit more
> of its internal signals - but it's an idea I will keep in mind for a
> future filter.
> Regarding the envelopes, there are bunch of reasons why I decided to
> go with the linearization:
> - the envelopes already have a non-linear response (piecewise linear
> decay and release ; linear attack). Since they can be routed either to
> internal parameters (oscillator frequency, PWM) or external CV, I
> found it more consistent if they behaved similarly for all modulation
> destinations.
> - I gave a shot at the non-linear version too, and the main obstacle
> was that for a large range of the sustain parameter value, the
> attenuation was too strong.
> - The other filter/VCA boards I have so far have linear VCAs.
> Olivier
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