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  • Alain
    I though you might be interested to know that I ve just added another mod to my MP4. I ve added portamento to the filter cutoff keyboard tracking. It is
    Message 1 of 6 , Mar 24, 2010
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      I though you might be interested to know that I've just added another mod to my MP4. I've added portamento to the filter cutoff keyboard tracking. It is controlled by the same portamento knob as the oscillators. And that without adding any new circuits or components. Just re-routing some control voltages.

      I've simply disconnected one wire (pin 1) on connector 18 of KLM-355C (filter board) that was bringing the keyboard CV coming from KLM-356D to the filter. And installed a new wire connected to the left side of R202 on KLM-354 to connector 18 (pin 1). Effectively taking the keyboard control voltage of VCO 1 and using it also as filter keyboard follow. So the glide times are identical to that of VCO 1.

      Anyone interested to make this modification, just drop me a line, and I will show you exactly how to do it. It involves having some experience at soldering wires, and possessing a good welding iron (pen type).There is no risk of "overloading" the CV signal from VCO 1 since the input of the filter keyboard tracking CV is buffered by an op amp of very high impedance.

      Korg should have added a portamento feature to the filter cutoff in the first place (as on many Moog synths).

      Alain.
    • Alan Dicker
      Great stuff well done Alain.   One feature I always want on the monopoly was lagetto.  Where the portmanto/glide is only active when you hold more than one
      Message 2 of 6 , Mar 25, 2010
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        Great stuff well done Alain.
         
        One feature I always want on the monopoly was lagetto.  Where the portmanto/glide is only active when you hold more than one key.  Much like one the SH 101.
        I wonder if there is some way to take the action of the singel/multi trigger and apply it to the portmento on.off jack?
        Will have to look in to the more closley.

        --- On Thu, 25/3/10, Alain <hubertalain@...> wrote:

        From: Alain <hubertalain@...>
        Subject: [korg_mono-poly] New modification...
        To: korg_mono-poly@yahoogroups.com
        Date: Thursday, 25 March, 2010, 4:57

         
        I though you might be interested to know that I've just added another mod to my MP4. I've added portamento to the filter cutoff keyboard tracking. It is controlled by the same portamento knob as the oscillators. And that without adding any new circuits or components. Just re-routing some control voltages.

        I've simply disconnected one wire (pin 1) on connector 18 of KLM-355C (filter board) that was bringing the keyboard CV coming from KLM-356D to the filter. And installed a new wire connected to the left side of R202 on KLM-354 to connector 18 (pin 1). Effectively taking the keyboard control voltage of VCO 1 and using it also as filter keyboard follow. So the glide times are identical to that of VCO 1.

        Anyone interested to make this modification, just drop me a line, and I will show you exactly how to do it. It involves having some experience at soldering wires, and possessing a good welding iron (pen type).There is no risk of "overloading" the CV signal from VCO 1 since the input of the filter keyboard tracking CV is buffered by an op amp of very high impedance.

        Korg should have added a portamento feature to the filter cutoff in the first place (as on many Moog synths).

        Alain.


      • Florian Anwander
        Hello Alain ... Attention: The pinout has inverted between old and new version of KLM355 (You must read this with a monospace font like courier): PinOLD PinNew
        Message 3 of 6 , Mar 25, 2010
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          Hello Alain


          > I've simply disconnected one wire (pin 1) on
          > connector 18 of KLM-355C (filter board) that was bringing the
          > keyboard CV coming from KLM-356D to the filter.
          Attention:
          The pinout has inverted between old and new version of KLM355 (You must
          read this with a monospace font like courier):

          PinOLD PinNew
          KEYBD-TRACK 1 3
          SINGLE-TRIG 2 2
          MULTI-TRIG 3 1

          > So the glide times are identical to that of VCO 1.
          This will be useful only in Unisono and Chord-Memory modes!!! In
          Unisono/Share and Poly modes the VCF should follow the CV of the highest
          VCO (that is what pin20-1 is delivering) - which is not necessarily
          VCO1. In the opposite: VCO1 is typically the lowest note (in Unisono/Share).

          > Korg should have added a portamento feature to the filter cutoff
          > in the first place (as on many Moog synths).
          I think Korg did it because of the mentioned dependency. And also they
          used a fourfolded potentiometer, which is already difficult to get, but
          a fivefolded seems close to impossible

          The better solution would have been (or would be) to establishe five
          voltage controlled portamentos, where the fifth portamento affects the
          KBD voltage of pin20-1/3

          Florian
        • Florian Anwander
          Hi Alan ... I assume you wanted to write legato ;-) ... I did not try this, but it should not be too difficult: there is an input jack for portamento and a
          Message 4 of 6 , Mar 25, 2010
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            Hi Alan

            > One feature I always want on the monopoly was lagetto.
            I assume you wanted to write "legato" ;-)

            > Where the
            > portmanto/glide is only active when you hold more than one key. Much
            > like one the SH 101.
            > I wonder if there is some way to take the action of the singel/multi
            > trigger and apply it to the portmento on.off jack?
            I did not try this, but it should not be too difficult: there is an
            input jack for portamento and a trigger out jack which can be set to
            negative gate. Connect thos jacks. Then set the trigger switch at the
            front to single and you're done.

            Florian
          • Alain
            Hello Florian. You re absolutely right about the different pinout! I should have taken a closer look at those schematics. I have the new version of the
            Message 5 of 6 , Mar 25, 2010
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              Hello Florian.

              You're absolutely right about the different pinout! I should have taken a closer look at those schematics. I have the new version of the KLM-255C board, and it is indeed pin 3 and NOT pin 1 that I've disconnected. But I had confirmed the presence of the keyboard CV on that pin with a Voltmeter before doing anything else. When I saw 1 volt change per octave, I knew it was the right pin. I'm terribly sorry for the mix up.

              As for the behavior in other key assign modes, it's true that it will be different than before since it will always follow OSC 1 now. And in Unison/Share mode it will be somewhat unpredictable depending on note assignment. But in Poly mode, you can play in a manner to have the first oscillator play a note in a chord that will reflect the cutoff value you want, with a little practice.

              If I find it too awkward to use in Unison/Share and Poly mode this way, I might just install a micro toggle switch to flip between original wiring and glide wiring...

              I wanted my mod to be as simple and "noninvasive" as possible, so that's why I used OSC 1 as source. Of course, anyone of the four oscillators pitch CV could do as well.

              I know it's not a terribly useful feature to have a portamento on filter cutoff, but in order to play Tony Banks early Genesis ARP type synth solos (without using an actual ARP synth), you need it. Moreover, the type of portamento on the MP4 is logarithmic which is the same type used many ARP synths, as opposed to the linear ones used on the Moogs. To be truthful, I play the Mono/Poly as a great monophonic synth most of the time as I have other true (better) analog polyphonic synths to play chords. And I prefer the on/off pedal switching control of the glide on the MP4 to the manual toggle switch on the Minimoog.

              Thanks again Florian, for pointing out very interesting facts. And making me aware of my pinout identification mistake! Next time I'll be more careful of what I write...

              Alain.

              --- In korg_mono-poly@yahoogroups.com, Florian Anwander <fanwander@...> wrote:
              >
              > Hello Alain
              >
              >
              > > I've simply disconnected one wire (pin 1) on
              > > connector 18 of KLM-355C (filter board) that was bringing the
              > > keyboard CV coming from KLM-356D to the filter.
              > Attention:
              > The pinout has inverted between old and new version of KLM355 (You must
              > read this with a monospace font like courier):
              >
              > PinOLD PinNew
              > KEYBD-TRACK 1 3
              > SINGLE-TRIG 2 2
              > MULTI-TRIG 3 1
              >
              > > So the glide times are identical to that of VCO 1.
              > This will be useful only in Unisono and Chord-Memory modes!!! In
              > Unisono/Share and Poly modes the VCF should follow the CV of the highest
              > VCO (that is what pin20-1 is delivering) - which is not necessarily
              > VCO1. In the opposite: VCO1 is typically the lowest note (in Unisono/Share).
              >
              > > Korg should have added a portamento feature to the filter cutoff
              > > in the first place (as on many Moog synths).
              > I think Korg did it because of the mentioned dependency. And also they
              > used a fourfolded potentiometer, which is already difficult to get, but
              > a fivefolded seems close to impossible
              >
              > The better solution would have been (or would be) to establishe five
              > voltage controlled portamentos, where the fifth portamento affects the
              > KBD voltage of pin20-1/3
              >
              > Florian
              >
            • Alain
              Great idea Florian. But unfortunately, it doesn t quite work. Because the negative gate (S-trigger) trigger out setting, used to switch the portamento effect
              Message 6 of 6 , Mar 25, 2010
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                Great idea Florian. But unfortunately, it doesn't quite work. Because the negative gate (S-trigger) trigger out setting, used to switch the portamento effect off, is inverted relative to the internal envelope gate signal. The result is a very short delay in the portamento being switched off when two notes are played non-legato, instead of having no portamento at all. But that was a great idea nonetheless.

                Alain

                --- In korg_mono-poly@yahoogroups.com, Florian Anwander <fanwander@...> wrote:
                >
                > Hi Alan
                >
                > > One feature I always want on the monopoly was lagetto.
                > I assume you wanted to write "legato" ;-)
                >
                > > Where the
                > > portmanto/glide is only active when you hold more than one key. Much
                > > like one the SH 101.
                > > I wonder if there is some way to take the action of the singel/multi
                > > trigger and apply it to the portmento on.off jack?
                > I did not try this, but it should not be too difficult: there is an
                > input jack for portamento and a trigger out jack which can be set to
                > negative gate. Connect thos jacks. Then set the trigger switch at the
                > front to single and you're done.
                >
                > Florian
                >
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