[sdiy] SSM2164 panning curve

[Derek Holzer]

I've got a hopefully simple question about using the SSM2164 as a 
joystick controlled quadraphonic spatializer/panner. I have been looking 
at Marc Bareille's Quad VCA/CV-Mixer as a good model for this project:

http://m.bareille.free.fr/modular1/quadvca/quadvca.htm

with some additions for the joystick control:

http://electro-music.com/forum/viewtopic.php?t=24705

My concern is this: when the joystick is it dead center the gain on all 
channels should be unity. However, for this particular gain/panning 
curve I don't want more than unity gain, only attenuation. I am aware 
that this nulls the effects of half the range of the joystick... however 
from what I have read this is the panning curve used by the Serge and 
Buchla spatializers, and it makes sense acoustically to me.

So let's assume that set up the SSM2164 as in the datasheet, where 0V is 
unity and minus voltage is attentuation. And I wire up my joysticks as 
voltage dividers between +15 and -15 (or should it be +/-5V?). But since 
I don't want any amplification, I use a diode to block the positive 
voltage coming from the joysticks, making sure the diode is rated not to 
break down anywhere near 15V (or 5V?). Am I on the right track? Or is 
there a way to set up the SSM2164 itself so that it only attenuates?

Thx+best!
Derek
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