J9 Input Balancing Jumper: For many systems you can leave this jumper in the UNBALANCED position. In other systems, the source unit may look for a ground through the RCA connection to the amplifier and create a ground loop, which in turn can cause a whine (not the type that comes in a bottle) in your system. In that event, you should set this jumper to BALANCED.
J10 PFM Jumper: The PFM (Programmable Frequency Match) Filter controls the cutoff frequency of the subwoofer output. The PFM is the bottom limit for the low pass output and will help protect your speakers.
J11 Front to Sub Jumper: If your source unit has front, rear, and subwoofer RCA Line Level outputs, connect them to the corresponding inputs on your DQDX. If your source unit has only front and rear inputs, just connect these to the front and rear inputs on the DQDX and switch this “Sub to Front” jumper to the ON position. Changing this jumper to ON will route the low pass signal (as defined by your crossover selection) to the Sub outputs of the DQDX.
J12 Ground Isolation Selector: Alternator noise may appear in a system because the source unit and amplifier(s) are using different grounding schemes. To help in this situation, we have provided alternative grounding connections. Make sure your system is turned OFF before you move these jumpers. We ship them in the isolated position, which usually gives the best results.