




                        P O L Y S I X   A D D I T I O N S :



1.    Overview - new Features
1.1.  HOLD Footswitch
1.2.  Noise Generator
1.3.  VCO Waveform
1.4.  Modulation Wheel
1.5.  BEND Wheel
1.6.  Patch RAM


2.    Revision history




1.    Overview - new Features
      Before doing any harm to your beloved POLYSIX read carefully all
      of this document and decide then what you want to implement.
      Refer to the attached schematics and to the P6 service manual.

1.1.  HOLD Footswitch
      One of the (few) annoying things of the POLYSIX is the lack of a
      sustain or hold pedal. So, after a few weeks I made my first
      modification to my POLYSIX. Later on I incorporated it into the
      extension PCB 'EP1'. Since I did not want to drill any holes into
      the back panel of my favourite synth I sacrificed the CHORD MEMORY
      footswitch, which I didn't use anyway, instead.
      On EP1 there is some circuit which generates a short pulse each time
      the footswitch is depressed AND released. this pulse is then used to
      'press' a switch in parallel to the HOLD button. You can do this like
      this:
                                        1N4148
                         ____        |/---|<----  KLM-366/IC6/pin27
         from EP1  o----|____|-------|
                         4k7         |\>--------  KLM-366/IC6/pin21
                                    BC547

      This approach is a very simple one and it has a drawback:
      If you play some notes and hold them with the footswitch, then release
      the footswitch all the notes will stop sounding. But with some exercise
      you can accomodate your style of using the footswitch.
      A second thing I have done to the HOLD footswitch is to switch also
      the ARPEGGIATOR LATCH mode ON and OFF. To achieve this you have to
      do a small modification to the KLM-366 board:
      - Cut connection IC1/pin6 to IC6/pin21 near IC1.
      - Connect IC1/pin6 to IC6/pin22.
      This routes the CHORD MEMORY footswitch input to switch the ARP LATCH
      ON / OFF. The front panel ARP LATCH switch must be OFF.

1.2.  Noise Generator
      A WHITE NOISE noise generator is built on EP1. Control is fully
      memorized with patches. It is switched on when waveform sawtooth or
      pulse is selected and PWM SPEED is greater than "1" (adjusted by trim
      pot P2 'TURN ON THRESHOLD'). PWM SPEED acts also as NOISE VOLUME
      control (adjust balance noise - VCO signal with trim pot P1 'NOISE
      LEVEL'). The nopise signal is AC coupled and fed to the VCO saw/pulse/
      sub osc. summing node of each voice on KLM-366 via a 33k resistor.
      The noise is generated digitally by means of a looped shift register.
      That means it is not really white noise but it is good enough and
      easy to implement.
      You can obtain PWM signal (not saw & not pulse) from KLM-367 IC1/pin6
      and PWM SPEED control voltage from KLM-367 IC13/pin1.
      +5V and -5V are also needed for EP1.

1.3.  VCO Waveform
      This is a very simple though effective mod: remove D1 from KLM-366
      and you get both sawtooth and pulse wave at the same time when saw
      is selected. The pulse wave can be turned off by setting the PW/PWM
      control to '10'.



1.4.  Modulation Wheel
      I wanted the mod wheel to be the same effect as the programmed
      modulation. (Did you ever use tremolo and vibrato with the same
      frequency and phase at the same time??)
      To follow the modulation wheel the programmed modulation mode you
      have to:
      - Mount a pnp transistor (eg BC557) in parallel to Q4 of KLM-367;
        collector to collector, base to base.
      - Connect to emitter a 22k resistor.
      - Connect to this resistor a control voltage -5V..0V.
      - You may add a second 22k resistor to the emitter to generate an
        input for a modulation pedal (10k log); 1/4" stereo jack:
                tip is -5V (via 1k safety resistor)
                ring is CV input
                sleeve is GND

      To get the -5V..0V out of the mod wheel you have to:
      - Connect the 'upper' end of mod wheel pot (former 'LFO' signal) to
        0V (GND); former 'lower' end.
      - Connect 'lower' end of mod wheel pot to -5V (pitch bend pot 'lower'
        end.
      - The middle pin of mod wheel pot is now control voltage -5V..0V.

1.5.  BEND Wheel
      I thought it would be nice also to bend the filter, not only the VCO.
      Here it is (memorized with patch):
      - Remove IC34 from KLM-367 and insert a DIL14 socket instead.
      - Connect IC34 socket/pin2 to -5V.
        BE CAREFUL! -5V will damage any logic IC!
      - Connect IC34 socket/pin9 to signal P13 (IC22/pin30; CN10/pin5).
      - Build extension PCB EP2 in this way that you can plug it into socket
        IC34 on KLM-367. Observe mechanical space at KBD assembly.
      - Find wire from (pitch) bend pot, middle pin and insert EP2:

                       +5V
                        o
                        |
                       +++
                       | |    BEND      VCO BEND
                 GND|--+ |<----------//--------------  .. to KLM-369 VR3
                       | |          |  |
                       +++          V  V
                        |          to EP2
                        o
                       -5V

      - Connect EP2/VCF BEND to KLM-366 IC13/pin2 (VCF CV summing node) via
        27k resistor.
      - On KLM-370 lift D3/anode and connect it to D1/anode. Mount additional
        diode (1N4148): anode to D2/anode, cathode to D3/cathode.
        This will encode the EFFECT MODE onto 2 bits and free one bit needed
        for memorizing VCO/VCF BEND.
      - Mount a switch onto the control panel e.g. into the plastic where the
        wheels are located. Connect the switch as indicated in the EP2
        schematics.

      The BEND MODE switch will now be memorized with the patches. Check the
      EFFECTS MODE of your patches. Probably it has to be reprogrammed.
      The BEND pot on KLM-370 affects only the pitch bend range; VCF bend is
      always full range.



1.6.  Patch RAM
      The patch memory can be doubled (from 32 sounds to 64 sounds) easily:
      - Purchase a 4kbit (1kx4) low power static RAM chip, DIL18 (e.g. 2114,
        Hitachi HM6148HPL, Toshiba TC5514). (If you still can get one!)
      - On KLM-367: cut connection between IC32/pin8 and IC25/pin11 (RAM nCS).
      - Connect IC32/pin8 to IC32/pin18 via 10k resistor (pullup for inactive
        chip).
      - Solder new purchased RAM chip onto existing one (IC32); all pins
        except for pin 8.
      - Connect pin8 of new RAM chip to pin 18 via 10k resistor (pullup for
        inactive chip).
      - Mount a switch onto the control panel (similar to BEND MODE switch)
        and connect middle pin of switch to KLM-367 IC25/pin11. Connect
        other two pins to RAM chips pin 8 each.

                                |----------o  RAM chip 1 pin 8
             IC25/pin11 o------/
                                |----------o  RAM chip 2 pin 8

      You can now select one of the two sets of 32 patches. Tape interface
      is also working with both sets.



2.    Revision history

      I did these things some time ago. I just wrote it down these days.
      Maybe I would have done it different now. I also made the key assign
      mode memorized, but this is very complicated and is not 100% reliable.

      If you have any suggestions please tell me; my email address is:

          johannes.hausensteiner@topcall.co.at


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