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Operation Modes
4
Mode Selection
The rear panel Mode Select Switch determines whether the amplifier is
in stereo, parallel or bridged mono mode. Do not operate the Mode
Select Switch with the amplifier on. See the next chapter on
Connections for proper wiring in each mode.
Stereo
For stereo (dual channel) operation, turn the amplifier off and set the
Mode Select Switch to the stereo position. In this mode, both channels
operate independently of each other, with their input attenuator con-
trolling their respective levels. Thus, a signal at Channel A’s input pro-
duces an amplified signal at Channel A’s output, while a signal at Channel
B’s input produces an amplified signal at Channel B’s output.
Parallel
For parallel (dual-channel/single input) operation, turn the amplifier off
and set the Mode Select Switch in the parallel position; both amplifier
channels are then driven by the signal at Channel A’s input. No jumper
wires are needed. Output connections are the same as in the stereo
mode. In the parallel mode, only Channel A’s input is active; Channel B’s
input is not in the circuit. Both input attenuator remain active, allowing
you to set different levels for each channel. Power and other general
performance specifications are the same as in the stereo mode.
Bridged Mono
Both amplifier channels can be bridged together to make a very pow-
erful single-channel monaural amplifier. Use extreme caution when
operating in the bridged mode, as potentially lethal voltage may be pre-
sent at the output terminals. To bridge the amplifier, turn the power off,
and set the rear panel mode select switch to the bridge position. Apply
the signal to Channel A’s input and connect the speakers across the hot
outputs (the “+” binding posts of channels A and B) or the Speakon con-
nector for Channel A.
Unlike the stereo and parallel modes, in which one side of each output
is grounded, both sides are hot in bridged mono mode. Channel A’s side
is the same polarity as the input.For proper operation,both input atten-
uator must be in the same position. This keeps the load balanced
between the channel outputs.
As in the parallel mode, only Channel A’s input is active. If an output
patch panel is used, all connections must be isolated from each other
and from the panel. For all models the recommended minimum nomi-
nal load impedance in the bridged mode is 4 Ohms (equivalent to dri-
ving both channels at 2 Ohms). Driving bridged loads of less than 4
Ohms will activate the ACL circuitry, resulting in a loss of power, and
may also cause a thermal overload.
Connecting amplifier
outputs to oscilloscopes
or other test equipment
while the amplifier is in
bridged mode may
damage both the amplifier
and test equipment!
a
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