Installation
Mechanical considerations
The Stewart Audio DA-70 Series amplifier occupies just one-
half standard rack space, is only 10.6” deep and weighs just
over 3 pounds, making it easier to install and transport than
almost any other comparable power amplifier. Still some
precautions are in order.
Rack mounting of the DA-70 Series may be achieved by using
either the Stewart Audio RMK-70-S or RMK-70-D rack kits.
The RMK-70-S centers the amplifier in a single rack space,
while the RMK-70-D allows you to rack two amps side by side
in a single rack space. For stability always use four screws to
affix the amplifier to the rack, preferably using rack washers
to avoid cosmetic damage to the rack mount panels. When
rack mounting your
DA-70 Series amplifiers be sure to remove the four adhesive
rubber feet from the bottom of the unit. The DA-70 Series
amplifiers can also be mounted to a standard rack shelf or
used as a stand alone product.
Thermal Considerations
Cooling of the DA-70 Series amplifiers is achieved by Stewart’s
unique whole chassis heatsink design, which utilizes the entire
chassis as a heatsink to cool the heat generating components
inside. In the event the internal ambient temperature reaches
85 degrees centigrade, the protection circuit will shut down
the power supply until the amplifier cools down.
Although the sophisticated thermal management system in the
DA-70 Series makes it less susceptible to overheating than
other amplifiers, it remains good practice to provide airspace
around the chassis. NOTE: A –4 (4 channel) amplifier will
dissipate twice the heat of a –2 (2 channel) amplifier and a
PFC model will dissipate approximately 10% more heat than a
non PFC model Therefore while a DA-70-2 runs very cool, the
DA-70-4-PFC will require a little more attention to cooling.
Multiple amplifiers can be racked on top of one another
without leaving a full rack space between them as long as
sufficient airflow is maintained to allow heat to escape out the
when power is not available from the wall. The power supply
must act as a local reservoir of power from which the ampli-
fier circuits draw. This storage function is responsible for
much of the bulk, weight and cost of traditional power
amplifiers.
High Frequency Switch Mode Power Supplies
Stewart’s famous, High Frequency Switch Mode Power Sup-
plies fully recharges 1000 times faster than conventional sup-
plies, requiring far less capacitance for filtering and storage.
This high-speed recharging reduces power supply “sagging”
common with other designs.
The
New DA-70 Series Digital Amplifiers
utilizes a new,
regulated, forward converter design Switch Mode Power Sup-
ply operating at a frequency 2/3 faster than our old standard
supply.
Power Factor Correction
Models with a PFC designation utilizes Power Factor Correc-
tion circuitry in their power supply. This circuitry automati-
cally adjusts the power supply to provide stable, full output
over a wide range of mains voltages, typically from 90VAC to
240VAC. This feature makes the DA-70 Series operable any-
where in the world, and is a very useful feature when
operating from unstable or questionable AC mains.
This power supply’s remarkable conversion efficiency com-
bined with Damped Ternary Modulation translates into major
savings of energy drawn from the AC line. The benefits are
reduced heat dissipation, and downsizing of most major
components. This saves space and weight without sacrificing
the Sonic excellence Stewart Audio is famous for.
Bridging
Bridging of the DA-70 Series is not possible due to the high
efficiency design of the Damped Ternary Modulation.
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