KORG Polysix V/Hz-problem

[Fraser, Colin J]

If you want a MIDI interface for your Polysix there are easier ways to go
about it.
I believe Kenton will provide a retrofit as will some other companies.

I designed my own Polysix midi interface, which works by fooling the
keyboard scanning matrix that keys are being pressed.
The principle probably applies to other poly keyboards so I'll give a little
bit of detail...

There are 8 lines from the Polysix's keyboard scanning circuit that are
connected to 8 groups of keys. All the lines are normally held at 5v, but
when a group of keys is to be scanned, the line for that group is pulled
low. If any key is pressed, then one of the 8 lines which run back to the
scanning circuit will be pulled low. The circuit detects this and knows the
key is pressed.

I built a board with 8 74LS374 octal latches on it. Each output enable line
for the latches was connected to one of the keyboard scanning lines.
A diode at each output of the latches effectively made them into open
collector outputs - they can pull a line low, but don't drive them high
high.
Then each set of 8 outputs from the latches is connected together, and
joined to the lines that return to the keyboard scanner.

A microprocessor with a midi interface receives note messages and sets the
latch outputs to 0 where a key is pressed.

This interface works alongside the keyboard - you can play notes on top of
notes played by midi - and also it allows you to use the arpeggiator and
chord memory over midi.
More details on request...


Colin f


> -----Original Message-----
> From: Bodin, Erik [mailto:Erik.Bodin at Skanska.se]
> Sent: 21 October 1998 14:34
> To: 'synth-diy at mailhost.bpa.nl'
> Subject: KORG Polysix V/Hz-problem
> 
> 
> I know about a unit that transforms MIDI signals to V/Hz. 8 
> outputs could be
> assigned (each) as V/Hz or gate. I.e. 4 voices is 
> controllable if the synth
> demands both V/Hz signal and gate per voice. But if the synth 
> only needs
> V/Hz signal 8 voices might be controlled.
> 
> Is it possible to connect these V/Hz outputs straight in to 
> the circuitboard
> on the Polysix. ? Where ?
> 
> Pleas anwer
> 
> Erik.bodin at skanska.se
>