Comparisions on the SP A700 & S600

[Life-Is-Good-Diver]

I'm getting back in the water again, after being out for the past year, and need to buy a set of regs again. I had the Scuba pro S600 in the past, and went to my local dive shop today to buy a S600, and they just had two Scubapros A700's come into the store today with the MK17 on them.

We hooked up both the A700's and the S600 onto a machine to see how much pressure it took to open the diaphragm on each.

The S600 was around 1.3 - 1.4 , and when we hooked up the A700 right outta the box, it was around .45 - .50 , big difference !

The S600 retails around $600.00, and the A700 with the MK25 was around $700.00. The shop is a Scuba pro dealer.

I went ahead and ordered the A700, and it's expected to come in June 26th

All though I was not crazy about the looks, and the 2nd stage did feel alittle heavier in my hand, I heard the WOB was half of the S600

I was a big fan of the S600, and wanted to see if anyone had any experiences yet with the A700.

He hasn't ordered the reg yet, as I told him to give me a day or two to check the specs etc against the S600

What are your thoughts between the S600 & A700?

Either one I'd be going with the MK25 1st stage, as I love the performance of that 1st stage

 

[halocline]

I'm sure that both regs can be tuned to around 1" cracking effort, but too much lower and you'll have problems with case fault geometry. Basically if the difference in depth between the exhaust valve and the diaphragm exceeds the cracking effort, the reg will free flow when oriented so that the exhaust valve is shallower by the largest amount.

Think of it this way; the pressure equalization on both sides of the diaphragm is what keeps the valve closed; as soon as there's a pressure drop on the dry side of the diaphragm (inside the case) the diaphragm collapses, pushing on the lever and that opens the reg, until pressure builds up inside to equalize, pushes the diaphragm back out, and the valve closes.

The exhaust valve is the one-way "out" valve, and as such puts a limit on how much pressure can exist inside the case. It is kept closed by ambient pressure on the outside of the case. If the reg is oriented so that the exhaust valve is, say 1" shallower than the diaphragm, then the limit on pressure inside the case is 1" less than the pressure at the diaphragm. So if the cracking effort is set too low, this small difference in pressure is enough to get a freeflow going. I've experienced this on my 109s.

That was the idea behind the D series; the exhaust valve is coaxial with the diaphragm, and so there is never significant difference between the depth of the two. As a result, the D series regs are extremely stable down to very low cracking efforts.

Since the cracking effort is so low on all of these regs, it's more of an academic point. Given the flow rates of these regs, if you think the WOB is high on either of them you might as well get a new hobby, you'll never be happy in scuba.

I would guess that the case fault geometry would be about the same on the S600 and the A700. Assuming the A700 is a full metal case reg with a metal airbarrel, I bet it's MUCH more pleasant to dive with than the S600, and if it's only $100 more, it's definitely worth giving a try.