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Which means that the gas throughput through the jet remains EXACTLY the same regardless of depth, and so your gas utilisation will not change based on depth, unlike open circuit.. I would assume that the regulator was like the O2 reg on the KISS, in that it has a fixed IP, and is not compensated for by depth but as I've not trained on them, I'd wait for someone else to confirm!
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This is correct. So long as the supply pressure is at least twice the downstream pressure then the sonic valve will deliver a "constant" mass of gas. The Cylinder gas consumption can be calculated in exactly the way outlined in the original post. The First stage is not depth compensated as stays at about an absolute IP of 17+1 Bar; so unless you take the unit to 80-ish meters, or so, expect it to work as planned. One other caviat - the IP will fall slightly once the cylinder pressure reaches about 30 Bar.
Other useful but reassuring facts: Each Sonic valve is in fact a double. If either blocks then the other should still add O2 containing gas such that if the VO2 is less than about 1.5 L/min then a hypoxic mix is avoided. Further, if a disaster occurs and both were to be blocked the IP will rise and the Second stage is then designed to leak fresh gas into the loop. This along with the system acting as open circuit reg. (if you flush the loop) should allow the remaining primary gas to be used before going to bailout. (just a further escape option so long as you know the loop PO2.)
Neil