Just put in my CDA-9855 and am trying to setup my Amp. The amp is a MRV-F405. It has a switch that you can select either "Nom" or "4V". The Amp manual says, if using a headunit with 4V preout, then select the "4V" option. However, if I select the 4V option, the music is much quiter. If I put it on "Nom" then its nice and loud just like my old unit (which is a 2v preout unit). Am I doing something wrong?? Should I just leave the Amp on "Nom"?? Also, even if I put it on 4V and crank the gain right up, the music doesnt change. I've checked all the crossover over settings and they are all correct (doubt that would affect it though).
Also, at the back of the CDA-9855 is a thick green cable which has a little silver box attached to it. On the box is written "4V DC/DC converter". There are no switches on this box, and it just hangs there. Can someone explain what this is?