Amp's preamp inputs when bridging two channels

[grampi 10+ year member]

I have a Kicker KX 600.4 amp which I will be running in 3 channel mode (channels 3 and 4 will be bridged for a sub output). When doing this, do I need to plug both the left and right channel RCA's from the HU's sub preamp out into the amp's input for channels 3 and 4, do I only need to plug one of them in, or doesn't it matter either way? The owner's manual doesn't address this issue.

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[thch 10+ year member]

normally both. the amp will normally combine the signals. (it actually reverses the polarity of one signal, then hooks it up backwards to the output terminals -- this allows you to get a signal and its opposite allowing double voltage, or just hook up two speakers) You can run the amp bridged with one input signal, but it means that one channel is disipating power (a lot of power at that) and acting as a wire (not contributing to output).

 

[grampi 10+ year member]

It just seems strange to use both preamp inputs when the amp is bridged. All of the amps I've used previous to this on have used only the left input in this configuration.