Attachments :
It's not too far fetched. I found this in the Synth DIY archives:
Jim Patchell wrote:
"One thing I have always wanted to try is based on a circuit based on
the quadrature sine wave oscilator that you will find in the Analog
Devices NonLinear Circuits handbook (page 80 in my copy). This
oscilator is basically a state variable filter. If you look at the
amplifier that controlls the resonance, it keeps the thing oscilating by
balancing positive and negative feed back. When the voltage exceeds a
certain amplitude, the zener diodes begin to conduct forcing negative
feedback. When the amplitude is low, the zeners don´t conduct, and you
only have positive feedback. In the Nov./Dec. 1980 issue of Polyphony,
you will find the same circuit, except implemented with CA3280´s instead
of analog multipliers. The article was written by some strange
character. :^)
If you use an OTA to control the resonance, and the OTA is
´´inverting´´, if you put a large resistor around the OTA, this resistor
will provide positive feedback when the OTA is at very low Gm values.
This might be enough to make it start to oscillate. By using some other
non-linear elements, you might be able to control the oscilations so
that it doesn´t run away. "
http://www.buchi.de/SDIY/ShowPost.ASP?29153
If it is based on a state variable design, it probably would need more modifying than simply slapping a sigal input onto the module. I'm fascinated by circuit like this, since it's a generative module with a processing module as its core. That's one reason I really like the DUSG - it can be generative and it can be a modifier.
-----Original Message-----
From: John Loffink [mailto:jloffink@...]
Sent: Sat 10/2/2004 6:23 PM
To: SergeModular@yahoogroups.com
Subject: [SergeModular] RE: QUO as VCF?
While a filter might be the basis for the Serge Quadrature Oscillator design
(I honestly don't know - haven't looked at the board), there is no input for
filtering. Also, the frequency is limited to 500 Hz even with external
control voltage inputs.
This is an excellent module for panning control however since it has the
built in VCAs/attenuators and the Serge VC pan does not have a CV
attenuator.
John Loffink
The Microtonal Synthesis Web Site
http://www.microtonal-synthesis.com
The Wavemakers Synthesizer Web Site
http://www.wavemakers-synth.com
Yahoo! Groups Sponsor
ADVERTISEMENT
click here <http://us.ard.yahoo.com/SIG=1298uqg7u/M=315388.5455589.6541277.2248467/D=grplch/S=1705032144:HM/EXP=1096853008/A=2372354/R=0/SIG=12id813k2/*https://www.orchardbank.com/hcs/hcsapplication?pf=PLApply&media=EMYHNL40F21004SS>
<http://us.adserver.yahoo.com/l?M=315388.5455589.6541277.2248467/D=grplch/S=:HM/A=2372354/rand=512420373>
________________________________
Yahoo! Groups Links
* To visit your group on the web, go to:
http://groups.yahoo.com/group/SergeModular/
* To unsubscribe from this group, send an email to:
SergeModular-unsubscribe@yahoogroups.com <mailto:SergeModular-unsubscribe@yahoogroups.com?subject=Unsubscribe>
* Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service <http://docs.yahoo.com/info/terms/> .
Jim Patchell wrote:
"One thing I have always wanted to try is based on a circuit based on
the quadrature sine wave oscilator that you will find in the Analog
Devices NonLinear Circuits handbook (page 80 in my copy). This
oscilator is basically a state variable filter. If you look at the
amplifier that controlls the resonance, it keeps the thing oscilating by
balancing positive and negative feed back. When the voltage exceeds a
certain amplitude, the zener diodes begin to conduct forcing negative
feedback. When the amplitude is low, the zeners don´t conduct, and you
only have positive feedback. In the Nov./Dec. 1980 issue of Polyphony,
you will find the same circuit, except implemented with CA3280´s instead
of analog multipliers. The article was written by some strange
character. :^)
If you use an OTA to control the resonance, and the OTA is
´´inverting´´, if you put a large resistor around the OTA, this resistor
will provide positive feedback when the OTA is at very low Gm values.
This might be enough to make it start to oscillate. By using some other
non-linear elements, you might be able to control the oscilations so
that it doesn´t run away. "
http://www.buchi.de/SDIY/ShowPost.ASP?29153
If it is based on a state variable design, it probably would need more modifying than simply slapping a sigal input onto the module. I'm fascinated by circuit like this, since it's a generative module with a processing module as its core. That's one reason I really like the DUSG - it can be generative and it can be a modifier.
-----Original Message-----
From: John Loffink [mailto:jloffink@...]
Sent: Sat 10/2/2004 6:23 PM
To: SergeModular@yahoogroups.com
Subject: [SergeModular] RE: QUO as VCF?
While a filter might be the basis for the Serge Quadrature Oscillator design
(I honestly don't know - haven't looked at the board), there is no input for
filtering. Also, the frequency is limited to 500 Hz even with external
control voltage inputs.
This is an excellent module for panning control however since it has the
built in VCAs/attenuators and the Serge VC pan does not have a CV
attenuator.
John Loffink
The Microtonal Synthesis Web Site
http://www.microtonal-synthesis.com
The Wavemakers Synthesizer Web Site
http://www.wavemakers-synth.com
> -----Original Message-----Keep on Patchin'!
> From: Fahl, Romeo [mailto:rfahl@...]
> Sent: Saturday, October 02, 2004 8:01 PM
> To: SergeModular@yahoogroups.com
> Subject: QUO as VCF?
>
> Has anyone tinkered with using their QUO as a VCF? Isn't it just a state
> variable VCF with high feedback to the point of oscillating? There was an
> Electronotes 4 Pole VCF that was also presented as a sine/cosine
> oscillator, which I hear is a nice little module.
Yahoo! Groups Sponsor
ADVERTISEMENT
click here <http://us.ard.yahoo.com/SIG=1298uqg7u/M=315388.5455589.6541277.2248467/D=grplch/S=1705032144:HM/EXP=1096853008/A=2372354/R=0/SIG=12id813k2/*https://www.orchardbank.com/hcs/hcsapplication?pf=PLApply&media=EMYHNL40F21004SS>
<http://us.adserver.yahoo.com/l?M=315388.5455589.6541277.2248467/D=grplch/S=:HM/A=2372354/rand=512420373>
________________________________
Yahoo! Groups Links
* To visit your group on the web, go to:
http://groups.yahoo.com/group/SergeModular/
* To unsubscribe from this group, send an email to:
SergeModular-unsubscribe@yahoogroups.com <mailto:SergeModular-unsubscribe@yahoogroups.com?subject=Unsubscribe>
* Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service <http://docs.yahoo.com/info/terms/> .