[sdiy] Dual Functional Input - A Bad Idea?

[Scott Stites]

Hi List,

I've got an idea for enabling dual functionality to my Dim C remote bypass jack.  It's configured to toggle the bypass with a positive pulse from a synth module.  I like that, but I also like being able to toggle bypass with a momentary foot switch.  My thought is to use a C&K 7213 switch, which is like the marvelously useful C&K 7211, except that one of the positions is momentary.  Flipping to the momentary position from center will toggle bypass manually, leaving it in center will allow pulses on the remote bypass input to toggle bypass, and in the up position will allow a footswitch connected to the remote input to toggle bypass.  This scheme allows the additional functionality without adding any more front panel parts.

Since I'm going to be the one using this thing, I figure I better idiot-proof it, and that's where my question comes in:  in order to configure the jack for footswitch operation, I'll have to run 9V through a resistor to the footswitch, and the footswitch will ground the 9V through the resistor, allowing things to trigger.  However, because it's a dual purpose jack, there could be a situation where a module is plugged into it (say an LFO or EG) and *someone* accidentally switches the thing to footswitch operation.  In this case, +9V will be going through a resistor and protection diode into the output of the attached module.  The resistor will certainly limit current to a very small amount, but the question remaining is: is this entirely kosher or a Bad Idea?

The protection diode, BTW, is to prevent anything greater than the +9V from going back through the 9V (in case an excessive CV is input in the same accidental situation - I have modules that could try to do that).  Negative input voltages would be handled with another diode to ground.

Tanks,
Scott

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