AW: Linear VCO Midi'ing?

J.D. McEachin jdm at
Mon Oct 14 00:56:58 CEST 1996

At 11:15 AM 10/10/96 PDT, Haible_Juergen#Tel2743 wrote:
>>I have the fine job <ackk!> of being asked to add Midi control to a Yamaha
>>GX-1 synth. (formerly Keith Emerson's.)
>>This beast has linear tracking VCO's and is very similar to two CS-80s for
>>my purposes.
>>I will not be supporting the pedal or solo voices.
>>I've heard that Kenton has some linear version Midi to CV units for Korgs
>>and CS-80s.
>>Does anybody know more about these or other units? Do they make a Pro/4
>>linear version?
>>I have to control 16 voices and several channels of continuous controllers
>>along with patch change capability (this might be the hardest part
>So it's actually *polyphonic* Midi control for linear VCOs that you need ! 
>I would highly recommend not to control the VCOs directly, but to connect
>CMOS switches parallel to the keyboard switches (if it is in any way similar
>to the CS- synths).
>The old Yamaha polysynths have a strange type of matrix: not the usual
>" 8 x something ", but an octaves-related "12 x something" matrix. I don't
>know if Kenton has something like this.
>But there is a solution by Doepfer: I bought a Midi Kit from them some
>years ago to midify my CX-3 organ. It uses a long shift register and latches
>to produce a gate signal for each separate note. There is also an option
>with CMOS switches and level shifters that should fit into almost every
>Prices were about DM200,- for the simple version, and about twice as
>much for the CMOS switch version. These were the kit prices; As far as I 
>they don't sell kits anymore. I have no idea if the whole thing is still in
>In my CX-3 I only needed the basic version plus a single NPN and a resistor,
>soldered across each key contact.

I believe that many of Kenton's MIDI retrofit kits work in this way as well
- a MIDI NoteOn is translated into a CMOS switch closure.  The advantage of
this method is that it's the least intrusive method, uses the board's voice
own assignment scheme, and doesn't require any sort of calibration.  Of
course, sometimes it's nice to have different voice assignment schemes, but
I don't think you're being paid for that.

You may want to email Richard Marshall (MARSHALLR at -
he knows a lot more about what Kenton has to offer in MIDI retrofit kits.

BTW, we'd love to know how the GX-1 compares to the CS-80, both sonically
and in controllability.


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