I agree with Herman.
With a Phoenix first stage, a DA Aqua Master is converted to a balanced Royal Aqua Master (we tend to call it a Phoenix Royal Aqua Master). There is mechanically no difference between the Phoenix RAM and a vintage RAM.
The Phoenix only adds all the ports, a replaceable volcano orifice, and a slightly improved air flow path.
It is perfectly acceptable to use a RAM, but make sure to save all the original parts since the regulator also has a high resale value in its vintage configuration.
The Voit equivalent to the Aqua Master is the: V66 Navy (cataloged 1962-1964).
But, like Herman mentioned, they are hard to find and have a very high value as a collectible. Again, the Phoenix conversion can always be reversed to its original vintage configuration.
BTW, the only difference between the Aqua Master and the Voit Navy is the front can with the label. The back, including the mechanism were probably all made by US Divers.
For more information about Voit you can look at this link:
Vintage Double Hose • View topic - Voit Double Hose Regulator Information