One thing to remember is that prior to the late 1960s or early 1970s, the single hose regulators did not have as good of breathing characteristics as a double hose (DA Aquamaster, which was the U.S. Navy's standard regulator). This is because the exhalation valve was too small. Double hose regulators breath very nicely on exhalation, due to the large opening and valve placement. Also, with few exceptions, early single hose regulators were tilt valves (upstream second stages) which breathed fairly hard. They were able to compete on inhalation resistance with the USD double hose regulators because of the difference in water pressure by placement of the demand valve at the mouth, instead of behind the head. In many positions, this improved the breathing characteristics because the diver did not have to overcome the hydrostatic "head" pressure between the valve and the center of the diver's lungs. But keep that in mind--single hose regulators of the earlier age were harder breathing, and not approved by the U.S. Navy for their divers. The first ones to gain approval were the AMF Voit MR-12 and the third generation Calypso from U.S. Divers Co. The later generation Conshelf regulator was also highly used, but only when it got the larger exhalation valve, by the U.S. Navy.
In the U.S. Air Force, we were using single hose regulators in the late 1960s, as they were much better for our types of operations, even with the smaller exhalation valves. We dove shallow, and used them in parascuba jumps, where a double hose regulator was problematical.
I have started collecting single hose regs too, and now have an Aquamatic, two first-generation Calypso (both of which i dive--I dove the AMF Voit version, the V11 Viking 40 when I was still a teenager), two Olympic 400 regs (still needing repair), and a Dacor Pacer (not really vintage, but a beautiful regulator anyway). Also is my collection is a Conshelf IV, a Healthways Scuba Star and several Sportsways Waterlung regulators.
SeaRat
