Hi Chris,
Yes, I think it should be not too difficult. I do not know about the
mechanical fit, though; I never owned a Poly-61.
The pitch bend connection (X-axis) is straight forward; both joystick
potis have a center tap, which has to be connected to 0V (GND) like it
is on the Pitch Bend Wheel. If you end up bending the wrong direction
just swap the two ends of the poti.
It might be that you don't get the full bend range as you did with the
wheel. This could be because the joystick poti active angle might be
less than the wheel poti active range. If so then experiment with
KLM-369 R17. It has a value of 680kOhms. If you replace it with a
lower value (e.g. 470k or 330k) you can extend the pitch bend range.
For modulation (Y-axis) connect the center tap to 0V as well. Both ends
of the poti to the LFO signal (former mod wheel "top") and the wiper to
the wire of the wiper of the previous mod wheel. This gives you
VCO modulation for both directions (moving the joystick upwards or
downwards). Again, for the range adjustment, experiment with KLM-369
R16 (original 430kOhms).
If you want to have VCO modulation in one direction and VCF modulation
in the other like it is on the Poly-61 (this is where the interesting
part starts :-) ) you will have to build a small circuit to correct for
level and bias of the LFO wave for both VCO and VCF. The LFO signal is
now connected to the poti wiper, the center tap is an GND, one end is
for VCO modulation, the other for VCF modulation:
_____
| |
+---------|OPAMP|---> VCO (KLM-369 R16)
| |_____|
|
/
LFO -------->\--+
/ |
| === _____
| | |
+---------|OPAMP|---> VCF (via res to KLM-366 IC10/pin2)
|_____|
The exact amplification and DC shift of the opamps is dependant on
several factors (level of LFO wave, active angle of joystick pot,
sensitivity of modulation inputs). So you have to try and find out...
You may want to mount a switch and select VCF or VCA modulation.
Or, since you already started ;-), may want to build a separate LFO,
like it is in the Poly-61.
Or you may mount another switch which lets you route the x-axis (bend)
to the VCF instead of VCO.
Or ...
:-) Johannes
On 2013-07-30 20:36, stannloo wrote:
> Does anyone know if it would be feasible and relatively easy to install the joystick from the Poly-61 onto the Polysix (replacing it).
>
> And ideally in a reversible manner...
>
> I kinda like the joystick.
> The black plastic modules seem to be the same, except one has wheels and the other has the joystick, to switching the modules seems like a piece of cake, but electrically and schematically... any issues?
>
> Thanks!
>
> -Chris from Synthosphere
>
>
>
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