This is probably a dumb question, but would it be possible to use the SV-1’s analog input in essentially DC-input mode? We want to monitor breathing (inhaling and exhaling) using either a piezo-belt or a gas pressure sensor; both supply a slowly changing AC signal. A reasonable device model for us might be for an input that exceeds a certain voltage to be registered as “voicing present”, and when the input goes below that voltage for a delay, for it to be “no voicing present”. I think that some voice-key setups would work fine with that, but others, especially if there is a high-pass filter involved, would not. So, would this work with the SV-1? (I could try it, but I’m afraid of frying something.) Oh–also, the range & current of the input voltage might be fairly important; maybe some kind of passive resistor/impedance-matching stuff might need to go in between the respiration monitor and the mic input.
I’m assuming that if this would work at all, the level-adjustment knobs could be used to change the settings.
I might also consider modulating the amplitude of a 1 KHz (?) sine wave with the output of the respiration monitor. This would be an active circuit, so a bit less convenient that just plugging the analog output of the respiration sensor into the SV-1, but it might not be too much of a problem. Presumably, this could be fed into the SV-1, but I’d also want to understand the interface requirements, to avoid blowing up the input.