Ok well in my particular case, my head unit is a sound card, but that really doesn't matter. (carpc) The problem is, I have the soundcard wired to the amps, and for some reason the signal coming out of the front and rear channels is way louder then that coming out of the bass channel. This is not a guess, many people have the same problem, the signal is actually different for the bass channel.
Anyway, I've never experienced a problem like this, and I just need to know the name of the part I need to boost that signal, so I can get some volume on my bass. Can this even be done? I've heard of something called a line driver preamp or something, this sounds like what I need.
Let me explain the problem specifically one last time so I'm sure you know what I'm talking about : I have a Cadence ZRS-9 Monoblock amp for my subwoofer. This is plenty of power for almost any sub, underpowering the sub is definately not the problem. I've hooked RCA cables coming out of an Ipod, and also from different channels of the soundcard into the amp, and the bass is very loud how it should be. However the signal from the actual bass channel of the soundcard is weak and even with the amp cranked to max power the bass is barely louder than the regular speakers.
Please provide details and be specific with names, and if possible provide links, this is my first time dealing with this aspect of car audio and I'm kind of in the dark here. Any help is appreciated.