elliottbnewcombjr
IF you go line level to sub, as yogi said after you split your preamp output into two left and two right, using the fitting he posted, or a pair of Y adapters ... you need to convert one l/r to mono for the sub ...That is not going to work with most preamplifiers, which typically have their outputs wired in parallel. If you convert one set of outputs to mono, you'll have converted all of the outputs to mono.