Core which has a pneumatically controlled second stage
Gemini which a mechanically controlled second stage?
Could you clarify, what you mean under Control?
May be Pneumatically Balanced?
Difference between Pneumatically Balanced and Unbalansed is:
Balanced has special chamber behind the valve, where is plunger with diameter little less than valve seat orifice.
When hose pressure (also called Intermediate Pressure or IP) will increase, than also will increase contra force to the seat seal. BUT it will increase slowly, than valve opening force. And than at pressure around 12-15-20 (depends on ajustment) bar you will have freeflow of your regulator second stage.
But this trick allow you to have more weak spring, and allow you to spent less forces for breath holding (keep valve opened).
In case of UNbalanced valve - you have just spring to make contra force to stay valve closed.
It has enough tension to keep valve closed up to 12-15 bar (depends on ajustment), and when IP will increase - you will have freeflow again.
So, as you have NOT additional contraforce - you must have more powerfull spring.
And when you start to breath - you have to keep opened valve with more strong force, than for balanced reg.
Red line - is force, required to keep breathing.
Later was invented Ventury effect, and some regulators like Mares Abyss receive special pipe that make force to keep bteathing, same as for balanced regulators etc...
So - all this is just for better understanging how it works
Major conclusion - does not matter, what kind of 2nd stage you are using, just freeflow IP means.
Anyway, with normal ajusted regulator you will not have problems with different stages.
P.S. But this coclusion not related to Aqualung Legend and another "Overbalanced" 1st stage regulators - there you have to use pneumobalanced 2ns stages.
P.P.S. but this remark is just for depth over 50m
Pneumatically CONTROLLED - Is Poseidon Jetstream or Xstream - it has special servo valve...
