hey guys. i have a headunit that is advertised as having a "high voltage, 5V" output. i recently purchased an alpine pdx amp and am having trouble setting the gains. the dial is labeled as follows: all the way to left is "min", which the manual says is 4 volts. At the top center of the dial, there is a sign that says "NOM". And all the way to the right is max. What should I set the gains at given i have a 5 volt output? I wanna get the most sound out of my amp as possible.