hey there. i have a 4 speaker system being powered by an alpine pdx 4.150. there is a switch for "input channel selector". there are three settings. (listed as they are in the manual):
a) Setting this switch to "1 + 3/ 2 + 4" will sum the CH-1 and CH-3 input and send it to CH-3 while the CH-2 and CH-4 inputs are summed and sent to CH-4.
b) Set this switch to "3/4" to have the inputs of CH-3/4 accept independent input signals. An example of this application would be the use of a head unit with dual pre-amp outputs.
c) Setting this switch to "1/2" will send the signal at the inputs of CH-1/2 to CH-3/4 of the PDX-4.150. This eliminates the need for "Y"-adaptors when using a head unit with a single pair of pre-amp output.
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there are 4 rca cables coming out of the headunit (two for the front and 2 for the rear). right now channel 1 is front left; channel 3 is rear left; channel 2 is front right; and channel 4 is rear right.
im not sure which of the three above settings i should use. any suggestions? thanks again guys.