Question on differences between Scubapro c200/c300. Cost vs. benefit

[TT_Vert]

If you had to choose between a balanced second stage or adjustable second which would you choose?

 

[redacted]

Most of my rigs have a balanced 2nd stage as a primary and an unbalanced adjustable 2nd stage as an alternate. For balanced 2nd stages I use Scubapro balanced adjustables (156) or a Scubapro coaxial valve Pilot or D-series. My unbalanced adjustables are all Scubapro 109s. I usually use a Scubapro R-series on my pony bottle or a G500 (balanced & adjustable) if I sling a stage bottle for longer dives.

 

[TT_Vert]

Given the choice of a Non adjustable but balanced 2nd and a balanced but nib adjustable 2nd at same price which would you opt for//

 

[redacted]

Within the barrel poppet design, I would probably go for the adjustable feature over the balanced feature since the difference in performance seems to be quite small. (I have the parts to convert all my 156s to 109 should I ever have a problem getting the 156 LP seats.) But if the balanced 2nd were a coaxial valve design, I would opt for that as the difference in performance is more noticeable.

 

[Zung]

If you had to choose between a balanced second stage or adjustable second which would you choose?

Simple answer: buy a G250V: it's both balanced and adjustable, plus it's not too expensive, in between the C300 and the S600, and finally it's the best breathing second that I know.

Complicated answer:
There are 2 basic ways to make a second:
One is called "barrel poppet", where the air is delivered through a barrel. It gives the smoothest delivery. It can be made balanced/unbalanced/adjustable/non-adjustable, and all the variations are good. The Scubapro G/S/C series work that way.
The other one is call "classic downstream", and it's not much more that a valve not unlike the one on your tires with a rod connecting it to the diaphragm. The air delivery is not as smooth as above. It can be made adjustable/non-adjustable, but not balanced.

So:
Balanced: always good
Adjustable balanced: always good
Unbalanced: sometimes good, sometimes less good
Adjustable unbalanced: always less good

Edit
"Good" above doesn't mean "best", there are variations inside each family. It's just a way to rough it out.

 

[halocline]

Complicated answer:
There are 2 basic ways to make a second:
One is called "barrel poppet", where the air is delivered through a barrel. It gives the smoothest delivery. It can be made balanced/unbalanced/adjustable/non-adjustable, and all the variations are good. The Scubapro G/S/C series work that way.
The other one is call "classic downstream", and it's not much more that a valve not unlike the one on your tires with a rod connecting it to the diaphragm. The air delivery is not as smooth as above. It can be made adjustable/non-adjustable, but not balanced.

Don't forget option 3: coaxial valve: such as the air1/D300/350/400, which are the best breathing 2nd stages I know of.
And, let's not leave out pilot/servo valves such as poseidons, and the old SP pilot. Complex to service, but certainly a successful design.

IMO the conventional 2nd stages (barrel poppet/downstream) are so popular because they're A)good enough B)inexpensive to make C)easy to service.

 

[eelnoraa]

choosing a reg based on ease of service is a good idea, but choosing one based on the so called "free parts for live" is not.

If you are doing only 30-40 dives a year on vacation, I would skip buying a reg entirely and just use rental.

 

[Zung]

I disagree: usually, rental gears are entry level, such as the like of SP MK2/R295, or AL Calypso. The difference with what we're talking here is quite noticeable.

I'd say it's the 3rd item to buy, after the mask and the fins.

 

[halocline]

choosing a reg based on ease of service is a good idea, but choosing one based on the so called "free parts for live" is not.

If you are doing only 30-40 dives a year on vacation, I would skip buying a reg entirely and just use rental.

I agree with the first part of this statement but not the second. 30-40 dives/year is not as small a number as one might think, and the rental cost would quickly exceed that of buying a mid level regulator. 5-10 dives/year, sure I'd agree. And there are lots of certified divers (probably the majority) who only dive that much or less.

 

[DA Aquamaster]

I don't agree with the "adjustable unbalanced = always less good" comment.

For example, properly tuned and placed on a balanced first stage, a Scubapro "Adjustable" will breathe just as well as a "Balanced Adjustable".

I also prefer to describe the Air 1/D300,350,400 as using a "center balanced" valve design. The "co-axial" reference to the D series refers to the coaxial arrangement of the exhaust valve and diaphragm, not the design of the valve itself. "Coaxial" however does not describe the Air 1 as in the Air 1 (and the Pilot) the diaphragm is the exhaust valve.