Special Features
Stewart Audio’s new “Compact Series” Power Amplifiers utilizes the latest
in Digital Audio Technology. The new, all Digital DA Series Power Amplifiers
were developed by Stewart Audio’s Digital Audio Team and represent the
pinnacle of Stewart Audio technology and design.
Please take a few moments to read through this section of the manual,
which provides an overview of the features that makes this amplifier
unique.
How is the DA-70 Amplifier different from other Amplifiers?
The primary difference between the DA-70 Series and
other amplifiers is that it is all digital and it has much
higher efficiency. Current digital audio systems use
Class A/B amplifiers to amplify analog signals produced
by a DAC. Analog designs have low efficiencies because
of the power consumed in the active components as a
result of the voltage difference between the amplifier's
output and it's power supply. This continuous control of
the supply voltage results in peak efficiencies of about
50%. As a result a large power supply and heat sink
are required.
Class D switching amplifiers were developed to over-
come this problem by discretely connecting the load to
the power supply. Higher efficiency is achieved, but
Class D is still essentially an analog solution because it
utilizes an analog interface and control. Stewart’s ap-
proach was to develop a new Class D amplifier that
utilized digital control. This approach enables lower
cost through digital integration, as well as, eliminating
performance degradation due to analog component
variations.
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Trouble shooting
If you experience difficulty in operating your new DA-
70 Series amplifier, Chances are good that you will be
able to remedy the problem yourself using standard
troubleshooting techniques and the suggestions offered
in the troubleshooting table on the next page.
When wiring cables it is imperative that all connections
be made cleanly with no stray wire strands to short ter-
minals. Make sure the wire clamp screws are tight. For
proper connection all wire should be stripped to bare
approximately ¼ inch of wire. Make sure that the con-
nector set screw seats on copper, not insulation.
Keep in mind that other components in the system can
cause problems which may appear to be caused by the
amplifier; systematic troubleshooting will allow you to
isolate the source of difficulty.
If you fail to correct the problem by following the out-
lined chart on the next page,
do not attempt
to open
or repair the unit yourself.
Please contact Stewart Audio at 209.588.8111 to
obtain a Return Authorization (RA) Number and
shipping instructions
. Once an RA Number is ob-
tained, return the unit to Stewart Audio at the address
indicated on the RA Form. Refer to the enclosed War-
ranty information for Terms and Conditions of War-
ranty.
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