Ok I need some help! Right now I have a four channel amp running all four speakers with line converters coming from my head unit. i wanted to add a sub so I want to go to 3 channels. the thing I cant figure out is how to drive the rear speakers with the head unit.I disconnected the 3/4 channel outputs to hook up the sub but now I have no sound from the rears. How do I get sound back? I am trying to make all the changes from the amp area. Can I just put some RCA plugs on the rear L/R +/- wires and connect that to the RCA wires coming from the head unit to the amp with a y adapter? I hope this made sense. Any help would be appreciated! Thanks