Input Wiring
Your DA-70 Series amplifier is provided with a 3 con-
ductor Phoenix Type connector for each input.
The connector may be wired Balanced by connecting to
Ground – and + as marked on the chassis over each
input. If you wish to operate the amplifier unbalanced,
connect your line across Ground and + and add a
jumper from – to ground.
Output (Speaker) Wiring
Your DA-70 Series amplifier is provided with a two con-
ductor Phoenix Type connector for each output.
The connector may be wired by connecting the speaker
line to – and + as marked on the chassis over each
output.
Caution: Due to the ternary design of the output
stage Bridging of this product line is not possible.
Do not tie any output pin to any other pin or to
ground. Never connect any speaker terminal to
anything other than a single output pin.
WARNING:
Violation of this Caution may result in damage to
your amplifier and will void your Stewart Audio
Warranty.
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What is Damped Ternary Modulation?
Conventional Class D amplifiers utilize binary, or BI-state op-
eration. Binary consists of only two switching states, positive
power and negative power. Ternary, or tri-state operation,
consists of three switching states; positive, negative and a
zero power state. The third state is unique to this design.
During the time when neither supply connection is required,
both speaker terminals are connected to each other providing
damping to the loudspeaker, hence the name damped ter-
nary. The figure below shows the advantage of the damped
ternary compared to binary modulation for a sine wave. In
binary the cancellation of two full level signals is required for
small outputs. Thus, the amplifier is continuously providing
full output! This represents wasted power. It also produces
unwanted RF energy that must be kept from radiating. In
contrast, the damped ternary design only supplies power to
produce a signal.
Damped Ternary Advantage over Binary
In tests using the same hardware configured for ternary and
then for binary, ternary's high frequency energy at zero out-
put is attenuated over 20 dB below binary operating into the
same filter! This means higher efficiency and smaller filter
components.
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