Operation Modes
Stereo Operation
For stereo (dual channel) operation, turn the amplifier OFF and set the mode select switches to the stereo position. In this mode, the respective channels operate independently of each other, with their input attenuators controlling their respective levels. Thus, a signal at channel 1's input produces an amplified signal at channel 1's output, while a signal at channel 2's input produces an amplified signal at channel 2's output. The same applies to channels 3 and 4 when their respective mode switch is in the Stereo position.
Parallel Operation
For parallel operation
1 and channel 2 are strapped together to allow patching to another amplifier or to channels 3 or 4. Both input attenuators remain active, allowing you to set different levels for each channel. Power and other general performance specifications are the same as in Stereo mode. The same applies to channels 3 and 4 when their respective mode switch is in the Parallel position; the input connectors on channels 3 and 4 are strapped together to allow patching to another amplifier.
Bridged Mono Operation
Two amplifier channels (1 and 2 or 3 and 4, respectively), can be bridged together to make a very powerful single- channel monaural amplifier. Use extreme caution when operating in Bridged mode; potentially lethal voltage may be present at the output terminals. To bridge the amplifier, slide the rear panel amplifier mode select switch to the Bridge position. Direct the signal to channel 1's input and connect the speakers across the hot outputs (the “1+POS” and “2+NEG” Speakon® connector) for channel 1. As with Parallel mode, both input connectors are strapped together to drive the input of another amplifier. The same applies to channels 3 and 4. Connect the speakers across the “1+POS” and “2+NEG” Speakon connector for channel 3.
When operating in the bridged mode, both attenuators of a respective set of channels (i.e. channel 1 and 2 or 3 and 4) must be in the same position so the speaker load will be equally shared between the channels.
Unlike Stereo and Parallel modes, in which one side of each output is at ground, both sides are hot in Bridged mode. Channel 1's side is the same polarity as its input with the minimum nominal load impedance being 4 ohms (equivalent to driving both channels at 2 ohms) in Bridged mode. Driving bridged loads of less than 4 ohms will activate the DDT™ circuitry, resulting in a loss of power, and may also cause a thermal (overheating) overload.
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