About VCF's

Joe Farler 100673.3375 at CompuServe.COM
Thu Apr 11 11:35:17 CEST 1996


Gene was asking about 4-pole lowpass VCF's built from 3080 stages.

I haven't built one ( yet ) but I was looking at Roland filter schematics the
other day and found that the System 700 uses this type of design for its
VCF703,E,F and G.
This design has four 3080 OTA  stages each buffered with a CA3140.  The cap
value is 470p.  A fifth 3080 is used for resonance control -  the filter output
is fed back to the input via this 3080 . Resonance control is from a 100K pot or
from a CV jack input summed by an op amp  and feeding the 3080 pin 5 via a PNP
transistor.

I don't have a System 700 .  Does anyone out there have one with this type of
VCF?  How does it sound?

Joe Farler 




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