okay so after a couple of weeks of just dealing with it, I am now trying to get rid of the constant hiss in my car. thinking that it's a ground issue, i put the DMM under the hood, in the trunk, and behind the dash. under the hood is 13.98, trunk is 13.98, dash is 13.96. after this thinking that the .02 difference is doing anything I locate a better ground putting me at 13.98, hiss is still there. check over my gain setting on my AC 6XS and on all my amp, gains are turned to the lowest possible setting on both; hiss is still there. thinking it might be RCAs, swapped RCAs even ran them through center of car, hiss still there. maybe it's the power and signal wires crossing somewhere, nope not crossed. grounded RCAs, made hiss louder. put ground loop isolator inline and hiss is still there. I'm getting desperate, I'm thinking it's some sort of alternator ripple and considering put a capacitor in line. any other ideas of possible fixes? BTW it's a constant hiss and does not change with engine speed or volume.