CHAPTER 5: THE MM-10ACX SUBWOOFER
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ELECTRICAL SAFETY ISSUES

Pay close attention to these important electrical and safety
issues.
■The MM-10ACX requires a grounded outlet. Always use
a grounded outlet and plug.
■Do not use a ground-lifting adapter or cut the AC cable
ground pin.
■Do not exceed the current capability of the 20-amp AC
Input connector for the MM-10ACX. When looping
MM-10ACXs, consider the total current draw for all units
on the circuit, including the first.
■Make sure the AC power cable for the MM-10ACX has
the appropriate power plug (on the other end) for the
area in which you will operate the unit. In addition, the
AC power cable must be rated for the total current draw
of all MM-10ACXs looped from the power source.
■Do not operate the unit if the power cable is frayed or
broken.
■Keep all liquids away from the MM-10ACX to avoid haz-
ards from electrical shock.

THE MM-10ACX AUDIO IN CONNECTORS

The MM-10ACX includes three XLR female Audio In connec-
tors for Satellite 1, Satellite 2, and Subwoofer.
The XLR female Audio In connectors accept balanced audio
signals with an input impedance of 10 kOhm. The connec-
tors use the following wiring:
■Pin 1 — 220 kOhm to chassis and earth ground (ESD
clamped)
■Pin 2 — Signal (+)
■Pin 3 — Signal (–)
■Case — Earth (AC) ground and chassis
Pins 2 and 3 carry the input as a differential signal. Pin 1 is
connected to earth through a 220 kOhm, 1000 pF, 15 V
clamped network. This circuitry provides virtual ground lift
for audio frequencies while allowing unwanted signals to
bleed to ground. Make sure to use standard, balanced XLR
audio cables with all three pins connected on both ends.
Telescopic grounding is not recommended, and shorting an
input connector pin to the case may cause a ground loop,
resulting in hum.
TIP: If unwanted noise or hiss is produced by
the subwoofer, disconnect its input cable. If the
noise stops, there is most likely nothing wrong with
the subwoofer. To locate the source of the noise,
check the audio cable, source audio, and AC power.
Earth ground
Chassis ground
MM-10ACX Audio In Connectors: Satellite 1, Satellite 2, and Subwoofer