H2Andy:
i ended up with a little more cash than i thought, so...
which is the "better" second stage, the ATX 50 or the ATX 40?
Andy,
The TX series have a larger diaphragm and therefore total larger physical size.
The ATX series have a smaller diaphragm and smaller size.
The TX50 has a larger exhaust tee than the ATX50.
The TX, ATX, 40, and 50 series regulators have essentially the same Dive / Pre Dive selector on the left side of the second stage.
The 40 series second stages do not have the breathing adjustment knob on the left hand side of the regulator.
The 50 series regulators have the adjustment knob. This adjustment knob can be used to make the regulator perform more precisely as your depth changes. It can also be used to make minor changes in the breathing adjustment over time between service adjustments. These adjustments are considered by some divers to be unnecessary while others like to fiddle with them. The best part about this adjustment knob is that it does no harm and can be adjusted back without any disassembly of the regulator.
My choice would be to get the TX50 as your primary second stage, and the ATX50 for your secondary second stage. This would be my choice if TX40, TX50, ATX40, and ATX50 second stages were all available. Price may be a consideration to you, but for me it played a smaller role on the initial investment.
If the TX50 regulator is not available to you and the only options are the ATX40 and the ATX50 I would choose the ATX50 for both my primary and secondary second stages.
I use the adjustment available on the 50 series second stages to de-tune the backup second stage to help to prevent free flow at shallow depths and in strong currents such as entering the Devils System or other high flow systems. Do I need to make these adjustments? No, a properly adjusted backup should not free flow in these environments, but I like to add just a little extra insurance to the equation.
Good luck,
Mark Vlahos
