Combining Un-Balanced 1st-stage with Balanced 2nd stage regulator ?

[Zef]

Depending on the model year of the Calypso you purchased, you may not be limited to warm water diving.

Post 2018 model year Calypso 1st stages were certified EN250A and thus rated for use at and below 10c.

Here is link to a ScubaBoard discussion from 2019:

Aqualung Calypso getting better

Stopped by the LDS today and was inquiring about prices on regulators that I could use on my pony bottle. The owner of the shop recommended the Aqualung Calypso as an inexpensive possibility. I responded that my wife has a Calypso reg set and it is not recommended to use when water temp is...

scubaboard.com

-Z

 

[herman]

Not sure I deserve the comments but I do stand by my previous post. The main reason to balance a second stage is to maintain a constant cracking pressure as IP varies with an additional benefit of usually having a lighter spring. As long as the first stage keeps IP within a reasonable range, the diver will never know the difference between a balanced and an unbalanced first stage, fact of the matter is, most divers would not notice the difference in cracking pressure in a good quality unbalanced pair, esp if we are enjoying the dive and not obsessing over reg performance.

 

[Geo7]

This is a timely thread with great posts that highlight an uncommon approach to reg combinations. Through the years some of our reg gurus complained that major manufacturers paired balanced seconds only with balanced 1sts, when in fact a balanced 2nd can mitigate some of the shortcomings of an unbalanced 1st.

Scubapro now offers the new S270 balanced 2nd with the Mk2 plus Evo, and I recently got two of my students a great deal on a set each (note I am not in the diving industry, nor afiliated). Some divestore employee she met happened to see her reg and badmouthed it (jealous she did not buy a reg from him), saying it will breathe inadequately below 30 feet. Obviously depth has little to do with balancing regs for tank pressure, as IP in all these regs is depth-compensated (flow rates may differ with tank pressure for most 1st stages and it would be great to have high flow rate at 400 PSI at 130 feet, but even better not to be there with 400 PSI), but beyond that: I feel the message here is that a bulletproof and easy to service Calypso or Mk2 1st stage can deliver great performance with a balanced 2nd.

 

[halocline]

unbalanced regulators exhibit different IP at different tank pressures, well all regulators do but balanced ones are closer. So the IP at a tank pressure of 3600psi may be 125psi, but at 300psi it may be 150psi. Since you have a downstream second stage, you have to find out where the IP is going to be the highest throughout the tank pressure range and tune the second stage there. If you tune it at 125psi, then it will freeflow at 150psi, so you need to tune it at 150.

This is a flow by piston 1st stage, IP will decrease with tank pressure. Since it's a balanced 2nd stage, it will tolerate the change in IP from full to empy easily, no reason to worry about free flows.

 

[tbone1004]

This is a flow by piston 1st stage, IP will decrease with tank pressure. Since it's a balanced 2nd stage, it will tolerate the change in IP from full to empy easily, no reason to worry about free flows.

thanks, had unbalanced diaphragms in my head since I'm wrenching on some Poseidons and admittedly not familiar with the calypso. Weird how they exhibit opposite behavior!