Setting up my subwoofer

I have my amp and preamp setup in balanced mode so what I'm trying to understand this since my sub is already Amplified through its own amp how do I connect it to unbalanced

Please explain to me how I do it from the preamp to the amp from the preamp to the sub I'm not sure

Simple, RCA out from pre-amp into the sub, then adjust the sub’s crossover, volume, and phase. Finding the best crossover typically requires an SPL meter, but it can be done by ear. Finding the correct phase is easy to, but if you want me to detail it, I can. Finding the correct volume is also not difficult. 
 
Make sure to do the sub crawl to find the best position for the sub (if crossing over >60Hz, find the best spot close to the speakers.

OP:
I think what you are missing is that the balanced and RCA outputs are live. :) You can use both at once.
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