The all chrome plated marine brass first stage regulator is a balanced diaphragm design which is environmentally
sealed. The diaphragm membrane transmits the pressure changes to the internal mechanism eliminating the need for the surrounding water to enter the intricate
mechanism. The benefit of this type of first stage design is that none of the internal parts are exposed to contaminants such as salt, sand, chlorine or pool
acids. These environmental contaminants cause corrosion and mineral deposits to form on the internal mechanism deteriorating regulator performance.
TUSA has taken this concept one step further with the addition of a Dry Ambient Pressure Chamber. A standard diaphragm first stage regulator allows some water
to enter the main spring cavity. Although the cavity is not associated with the intricate internal components, it does allow the cold water to rest against
the primary diaphragm cooling the air that passes through the first stage. This colder air can promote second stage freeze up when diving in cold water. The
Dry Air Ambient Chamber prevents water contact with the diaphragm and spring maximizing performance, at any depth, in cold water conditions below 10°C (50°F). In addition the outside of this chamber is ribbed increasing the parts surface area thus acting like a radiator to increase heat
transfer further reducing the problems associated with cold water diving.
The first stage has two high flow low pressure ports (LP) and two standard LP ports along with two high pressure ports (HP). The high flow LP ports are positioned
near the diaphragm and offer up to a 15% increase in air flow.
The S-90 second stage is also a pneumatically balanced system. A small chamber positioned at the end of the poppet assembly traps air and forces the poppet back
against the intermediate pressure orifice. This provides decreased inhalation resistance and increases smooth breathing in all conditions. The lightweight compact
composite designed second stage is also equipped with a Venturi Adjustment Lever. This lever has two positions that are selectable by the diver. Use Surface" or
minimum setting when entering the water or on the surface, reducing the sensitivity and possible free flow of the second stage. Use the Dive" or maximum setting
for maximum air flow during the dive. The second stage comes standard with an orthodontic-conscious designed silicone mouthpiece.
- TUSA RS-790 INT (A-Clamp) Regulator, or:
- TUSA RS-790 DIN Regulator.
TUSA RS-790 Regulator Features Video:
First Stage (R-700)
Balanced diaphragm first stage with anti-freeze system.
Dry ambient pressure chamber ideal for temps below 10°C (50°F).
Ribbed section to increase heat transfer and resist freezing.
Nitrox Compatible to 40% (the recreational limits of nitrox).
2 H.P. ports & 4 L.P. (2 standard/2 high flow) ports.
High flow L.P. ports offer up to 15% increase in air flow.
Second Stage (S-90)
Lightweight, compact composite case design.
Pneumatically balanced system.
Venturi adjustment lever.
Ortho-consciously designed mouthpiece.
Hose Thread: 3/8"
Hose Length: 29" (74cm)
R-700 First Stage
Dry Ambient Pressure Chamber
The dry ambient pressure chamber on the R-700 prevents water contact with the diaphragm and spring maximizing
performance, at any depth, in cold water conditions below 50°F/10°C.
Ideal For Cold Water Environments
The R-700 is engineered for cold water diving. It features a ribbed top cap section that acts like a radiator
to increase the surface area for heat transfer. This design allows warming of the critical internal first stage
parts that can freeze due to the gas pressure drops and low temperatures.
High Flow Ports
Two high flow low pressure ports are available on the R-700 in addition to two standard LP ports and 2 HP ports. The
high flow ports are positioned near the diaphragm and offer up to a 15% increase in air flow.
S-90 Second Stage
Pneumatically Balanced System
The S-90 second stage is a pneumatically balanced design. A small chamber positioned at the end of the poppet assembly
traps air and forces the poppet back against the intermediate pressure orifice. This provides decreased inhalation
resistance and increases smooth breathing in all conditions.
Venturi Adjustment Lever
The S-90 is equipped with a built-in Venturi adjustment lever. Two positions are selectable by the diver. Use Surface
or the minimum setting when entering the water or on the surface, reducing the sensitivity and possible free flow of
the second stage. Use the Dive or maximum setting for maximum air flow during the dive.