Bi-N-Tic filter and CGS48 VCO combined
2005-06-12 by allanjhall
I've just finished my Bi-N-Tic filter and put some pictures up in
the Photos/AllanJHall folder. Like lots of my other modules it's
built in Doepfer / Analog System Eurocard format, but uses +/- 15
volt power.
I went for a bit different approach from usual, I've combined it
with a CGS48 VCO and omitted the VCO components from the Bi-N-Tic
board as it now uses the VCO for its sawtooth input. I have all VCO
functions as normal (it is a very stable VCO BTW) but also have full
Bi-N-Tic filter functions available too. I built a small pcb to add
sub out buffer and mixer functions, VCO hard sync, PWM and also an
amplifier for the VCO shaped sine output to bring it up to +/-5v. I
also biased saw and square outputs to bring them to +/-5V too. The
VCO has a 10 turn pot for Frequency, calibrated to 1 turn per octave
by using a 10 turn 200k preset connected to wiper, this replaces 1M
tune resistor (also need to remove diode and 100K resistor for this
mod) The "include pulse" switch connects the sub output from pin 11
of the 4024 to the sub mix for even more madness. I also reversed
the connections on the Damping pot to make it function more like a
resonance pot - it now adds more effect as it is turned clockwise -
perhaps this is the correct way to wire it? Not sure, but this works
for me.
This is an awesome filter, just finished it yesterday and I'm still
learning how to use it - WOW, not your usual VCF for sure! The sub
outs can be very low depending on VCO freqency setting and can add
nice rhythmic effects when mixed together, wide sweeps and
modulation of VCO frequency are interesting effects too
On my wish list for Rev 2 would be voltage control of damping and
bandwidth :-)
Many thanks to Ken for making this design available to us all
Allan
the Photos/AllanJHall folder. Like lots of my other modules it's
built in Doepfer / Analog System Eurocard format, but uses +/- 15
volt power.
I went for a bit different approach from usual, I've combined it
with a CGS48 VCO and omitted the VCO components from the Bi-N-Tic
board as it now uses the VCO for its sawtooth input. I have all VCO
functions as normal (it is a very stable VCO BTW) but also have full
Bi-N-Tic filter functions available too. I built a small pcb to add
sub out buffer and mixer functions, VCO hard sync, PWM and also an
amplifier for the VCO shaped sine output to bring it up to +/-5v. I
also biased saw and square outputs to bring them to +/-5V too. The
VCO has a 10 turn pot for Frequency, calibrated to 1 turn per octave
by using a 10 turn 200k preset connected to wiper, this replaces 1M
tune resistor (also need to remove diode and 100K resistor for this
mod) The "include pulse" switch connects the sub output from pin 11
of the 4024 to the sub mix for even more madness. I also reversed
the connections on the Damping pot to make it function more like a
resonance pot - it now adds more effect as it is turned clockwise -
perhaps this is the correct way to wire it? Not sure, but this works
for me.
This is an awesome filter, just finished it yesterday and I'm still
learning how to use it - WOW, not your usual VCF for sure! The sub
outs can be very low depending on VCO freqency setting and can add
nice rhythmic effects when mixed together, wide sweeps and
modulation of VCO frequency are interesting effects too
On my wish list for Rev 2 would be voltage control of damping and
bandwidth :-)
Many thanks to Ken for making this design available to us all
Allan