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QUO as VCF?

QUO as VCF?

2004-10-03 by Fahl, Romeo

Attachments :
    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.

    Re: QUO as VCF?

    2004-10-03 by John Loffink

    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
    Show quoted textHide quoted text
    > -----Original Message-----
    > 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.

    Re: QUO as VCF?

    2004-10-03 by John P

    Can't be... could it.? Because of the 'hold' input that freezes the
    waveform at that point.
    How would you implement that using a filter??? More likely a carefully
    done triangle generator with a sine convertor,

    Also, as John L just pointed out, there's no filtering input.

    Fahl, Romeo wrote:
    Show quoted textHide quoted text
    >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.
    >
    >
    >
    >Keep on Patchin'!
    >
    >Yahoo! Groups Links
    >
    >
    >
    >
    >
    >

    --
    m/n/m/l
    surreal electronic music, sound, noise
    http://mnml.soulcatcher.net

    Re: QUO as VCF?

    2004-10-03 by John Loffink

    John P's right. I forgot about that function. The hold resumes where it
    left off, so there's no way this could be done with a filter circuit. A
    quadrature triangle core with sine converters is the most likely
    implementation.

    John Loffink
    The Microtonal Synthesis Web Site
    http://www.microtonal-synthesis.com
    The Wavemakers Synthesizer Web Site
    http://www.wavemakers-synth.com
    Show quoted textHide quoted text
    > -----Original Message-----
    > From: John P [mailto:johnp299792@...]
    > Sent: Saturday, October 02, 2004 8:27 PM
    >
    > Can't be... could it.? Because of the 'hold' input that freezes the
    > waveform at that point.
    > How would you implement that using a filter??? More likely a carefully
    > done triangle generator with a sine convertor,
    >
    > Also, as John L just pointed out, there's no filtering input.
    >
    > Fahl, Romeo wrote:
    >
    > >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.
    > >

    Re: QUO as VCF?

    2004-10-04 by Fahl, Romeo

    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
      Show quoted textHide quoted text
      > -----Original Message-----
      > 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.




      Keep on Patchin'!




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      Re: QUO as VCF?

      2004-10-04 by John P

      Is this true? You can't run the frequency higher with an external CV?
      What happens? Does it choke up like the DSG?

      John Loffink wrote:
      Show quoted textHide quoted text
      >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.
      >
      >

      Re: QUO as VCF?

      2004-10-04 by John Loffink

      It just pins at 500 Hz. It doesn't choke, it just won't go any higher.

      John Loffink
      The Microtonal Synthesis Web Site
      http://www.microtonal-synthesis.com
      The Wavemakers Synthesizer Web Site
      http://www.wavemakers-synth.com
      Show quoted textHide quoted text
      > -----Original Message-----
      > From: John P [mailto:johnp299792@...]
      >
      >
      > Is this true? You can't run the frequency higher with an external CV?
      > What happens? Does it choke up like the DSG?
      >
      > John Loffink wrote:
      >
      > >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.
      > >
      > >

      Re: QUO as VCF?

      2004-10-04 by John P

      Soooo.... if this is the same quadrature osc that the FRS uses, then
      it's limited to up/downshifts of 500 hz?
      And, has this been a problem for anyone?

      John Loffink wrote:
      Show quoted textHide quoted text
      >It just pins at 500 Hz. It doesn't choke, it just won't go any higher.
      >
      >John Loffink
      >The Microtonal Synthesis Web Site
      >http://www.microtonal-synthesis.com
      >The Wavemakers Synthesizer Web Site
      >http://www.wavemakers-synth.com
      >
      >
      >
      >
      >>-----Original Message-----
      >>From: John P [mailto:johnp299792@...]
      >>
      >>
      >>Is this true? You can't run the frequency higher with an external CV?
      >>What happens? Does it choke up like the DSG?
      >>
      >>John Loffink wrote:
      >>
      >>
      >>
      >>>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.
      >>>
      >>>
      >>>
      >>>
      >
      >
      >
      >
      >
      >Keep on Patchin'!
      >
      >Yahoo! Groups Links
      >
      >
      >
      >
      >
      >
      >
      >
      >
      >

      --
      m/n/m/l
      surreal electronic music, sound, noise
      http://mnml.soulcatcher.net

      Re: QUO as VCF?

      2004-10-04 by Robert Roesler

      The QUO has a limited octave range. When I had mine built, Rex said that
      with a cap change (or was it cap and resistor), the upper limit could be
      raised, but at the expense of the lower limit.

      -b
      Show quoted textHide quoted text
      On 10/3/04 7:42 PM, "John Loffink" <jloffink@...> wrote:

      >
      > It just pins at 500 Hz. It doesn't choke, it just won't go any higher.
      >
      > John Loffink
      > The Microtonal Synthesis Web Site
      > http://www.microtonal-synthesis.com
      > The Wavemakers Synthesizer Web Site
      > http://www.wavemakers-synth.com
      >
      >
      >> -----Original Message-----
      >> From: John P [mailto:johnp299792@...]
      >>
      >>
      >> Is this true? You can't run the frequency higher with an external CV?
      >> What happens? Does it choke up like the DSG?
      >>
      >> John Loffink wrote:
      >>
      >>> 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.
      >>>
      >>>
      >
      >
      >
      >
      >
      > Keep on Patchin'!
      >
      > Yahoo! Groups Links
      >
      >
      >
      >
      >
      >
      >

      Re: QUO as VCF?

      2004-10-04 by Steve Ridley

      > John P's right. I forgot about that function. The hold resumes where it
      > left off, so there's no way this could be done with a filter circuit.

      Yes there is. You just reduce the frequency to zero. I've
      seen it done this way on an old cyclic panner, and it worked
      quite adequetely.

      How absolute is the Hold? If you use the QUO as
      a cyclic panner and hit Hold when it's panned hard
      left and come back an hour later, is it still there or
      does it drift slowly?

      > A quadrature triangle core with sine converters is the
      > most likely implementation.

      Is it? If the QUO is also used in the Frequency Shifter,
      a pure sine output would be essential. I think the filter
      method would give a less distorted sine wave.

      Anyone know for sure?


      Steve


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      Re: QUO as VCF?

      2004-10-04 by John P

      It'd be easy to tell if it drifts if you use the QUO for FM, into a
      PCO/NTO scaled input, with the scale cranked 100%, then hit the QUO
      'hold'. I don't have one.... anybody?

      Steve Ridley wrote:
      Show quoted textHide quoted text
      >How absolute is the Hold? If you use the QUO as
      >a cyclic panner and hit Hold when it's panned hard
      >left and come back an hour later, is it still there or
      >does it drift slowly?
      >
      >

      --
      m/n/m/l
      surreal electronic music, sound, noise
      http://mnml.soulcatcher.net

      THX 1138

      2004-10-04 by kirkdegiorgio

      Hey John - I just saw your post on AH regarding the DVD release of THX1138
      and you took the words right out of my mouth!

      I was hoping Walter Murch would mention which synths they used for the
      various hardware 'bleeps', etc but instead he came out with the 'synth bleeps
      were cliched for us' type quote and I was disappointed...

      HOWEVER - the quality of the movie and the restoration completely made up for this...

      the extras are great too - fantastic history of Zoetrope, etc...

      for those of you who haven't bought this historic piece of film history.. what are u

      waiting for?? ;-)

      Actually the attitude of Murch was similar to the recent documentary on the BBC
      Radiophonic Workshop where there was also an undercurrent that the 'glory days' of the
      workshop were pre-synth - when Delia Derbyshire, et al used
      organic sounds and tape manipulation... rather than when they acquired the large EMS
      modular, etc.

      KD

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