so you have an old style sub without an lfe input. if so then you run the fronts out from the pre-amp using speaker wire into the sub, out from the sub using speaker wire into the fronts. this filters the bass off of the front channels, so yes, you will want as much bass as possible output from the pre-amp (large setting high crossover). the sub should be setup to crossover the low frequency to itself and pass the higher frequency back out. all this is avoided if you have a rca type input on the sub. if that is the case then you use the pre-amps rca pre-out to the white rca input on the sub. if you connect it the later way then the pre-amp does the crossing over and not the sub. the later way is most common and best, but if you dont have any choice then you have to connect it like i said first. you dont need a y adapter like someone before said, you connect rcaout of preamp to white input on sub. a y adapter is only used for subs with an auto cuton feature as it allows the sub to turn on with lower levels of input sound, however it WILL NOT MAKE ANY DIFFERENCE after the sub has cuton, so unless your cable came with a y adapter then its a waste.