[sdiy] Question about ASM-1 state variable VCF

[Scott Bernardi]

I breadboarded a state variable VCF very similar to the ASM-1;
schematics are at:
http://members.home.net/sbernardi/elec/og2/og2_svfilter1.gif
http://members.home.net/sbernardi/elec/og2/og2_svfilter2.gif

1. I would like a nice sustained oscillation when the Q is turned up. I
get oscillation, but it is very frequency dependent and runs into
clipping. I notice the ASM-1 VCF has a Q limiter built around R32, D1,
D2, R31, and R30. There are two pins labeled Qpot and Qout.  How do you
connect the Q pot?

2. I was using TL074's; I notice Gene uses the CA3140, and Electronotes
recommends it also, for low phase shift across the integrators. Do these
make a difference in stability compared to TL074's?

3. Has anybody used the CEM3320 in a state variable connection (I've got
a few extra of these)?

Any tips you gurus have in getting stable Q and oscillation will be
appreciated.

-- 
Scott Bernardi
sbernardi at home.net