SergeModular

I've always been curious as to what is going on inside to obtain the variable slope.

Is it for instance crossfading between several different outputs tapped at different poles?

-nick

It is not done by crossfading, it is done by manipulating the CV's/currents that control the two filter stages. An ordinary VCF has the same CV to both stages, this has an additional control (Slope) that controls the first stage. And to complicate things even more the control inputs of the sections are interconnected in a way I don't really understand. I need to study it further to get it, will do when I have the time...and the will to take the panel apart!

/d

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1. Variable Slope VCF
Posted by: "nicholas_kent" zaum@... nicholas_kent
Date: Thu Feb 19, 2009 2:53 am ((PST))

I've always been curious as to what is going on inside to obtain the variable slope.

Is it for instance crossfading between several different outputs tapped at different poles?

-nick

Daniel Araya wrote

> It is not done by crossfading, it is done by manipulating the CV's/
> currents that control the two filter stages. An ordinary VCF has
> the same CV to both stages, this has an additional control (Slope)
> that controls the first stage. And to complicate things even more
> the control inputs of the sections are interconnected in a way I
> don't really understand. I need to study it further to get it, will
> do when I have the time...and the will to take the panel apart!

Thinking about what you said. It's supposed to have a range of 6db to
18db. So I would think that would be 1 pole to 3 poles with some sort
of separate control of the poles.

Maybe if you see evidence of 2 stages then maybe there are separate 1
pole and 2 pole filters with the 1 pole being mixed with the 12db
from full phase inverted to 0 to 100%. But that's a mixing theory not
a separate control on a stage theory you were mentioning

Though reading what you wrote maybe it's offsetting the second and
third pole cutoffs successively higher to decrease their combined
slope down to 6db. When they have the same cutoff the net result is
18db. Just guessing here.

I don't actually have the module but I've always been curious about
it since seeing it in the catalog.

nick

> Thinking about what you said. It's supposed to have a range of 6db

to

> 18db. So I would think that would be 1 pole to 3 poles with some

sort

> of separate control of the poles.

No, it 6dB to 12dB per octave, after that it just increases the
resonance, which makes it appear steeper. It's a 2 pole filter.



Steve