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I was messing with the settings on my Alpine M301 today and under "level" it gives the following selections: 0dB, -6dB, -12dB, -18dB. On the actual amplifier, there is a switch that allows you to select the input range, either 0.1V-2.0V or .5V-8.0V. I have the switch on .5V-8.0V since my Alpine 7893 HU puts out a 4V sub output. This is a little confusing, but what dB setting should I set the level to on my amplifier? I have it set to -6dB, assuming that since 4V is king of in the middle of .5-8V, and -6dB is somewhat in the middle of the entire range of settings. I would appreciate your help.