SV-1 with very slow AC input?

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.

Greg Shenaut

Hi Greg,

From reading the requirements, it’s almost as if we designed it to specifically exclude that application. The input is AC coupled and expecting inputs around 1mV. It’s then amplified, bandpass filtered, rectified and the detection is based on the amplitude and duration of the resulting envelope.

OTOH, our forthcoming StimTracker would be good for your application, though we have no ETA.


Thanks, Hisham. I’ll try something else.