Audio Control DQDX User Manual page 7

Under the Covers - Internal Jumpers
You can optimize your DQDX using most of the controls mounted on
the top of the chassis. However, we recognize there are situations where
advanced users may have the need to configure the DQDX for specific
applications. Therefore we have provided a few setting that are located
under the chassis top for limited access.
1 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.
2 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
from a symptom commonly known as "Speaker Explodus".
3 Ground Isolation Selector: Alternator noise may appear in a sys-
tem because the source unit and amplifier(s) are using different ground-
ing 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.
➊ ➋ ➌
page 7