QSC Audio MX 1000a - Manuel (Page 6)

6
IV. OUTPUTS
Four “touch-proof” binding posts—one pair per chan-
nel—on the rear panel allow speaker cable connections
to the amplifier outputs. The special design allows con-
nection of large diameter speaker cable while reducing
shock hazard due to the high output power of MXa
amplifiers. The “hot” terminal of each output pair is the red
one; the black one is signal ground.
If you are operating the amplifier in “bridged” mode,
connect the speaker load across the red terminals only;
the red terminal of Channel 1 then is “hot” or “in-phase.”
The red terminal of Channel 2 is not grounded, however,
so use the same precautions in handling and dressing
the wire that you would for the normal “hot” outputs.
CONTROLS AND DISPLAYS
The front panel-mounted attenuator controls are labeled
in dB of attenuation and are continuously adjustable from
0 dB (full gain) to
∞
(full kill).
The LED displays for each channel function as follows:
LED COLOR
PWR Green Main power supply active on this channel.
SIG Yellow Shows signal is present
CLIP Red Shows output capability is being
exceeded, with clipping distortion
PROT Red Shows when the output is muted by
protection circuitry.
Table 1: LED Display Operation
AC POWER
Any MXa Series amplifier can be wired for 100, 120, or
220–240 VAC, 50 or 60 Hz operation. Unless it is spe-
cially ordered, each amplifier is configured for the line
voltage in the market for which it is intended. For ex-
ample, those intended for Japan are 100 VAC; for North
and Central America, 120 VAC; for Europe and most of
Asia, 220–240 VAC.
The power cord has a plug for connecting to a standard
AC source. For 120-volt operation, the plug is a standard
15-ampere grounded NEMA fitting; it meets safety agency
requirements for current consumption of less than 12
amperes during “normal” operation, but peak current
draw under heavy usage can be much higher.
CLIP PROT PWR SIG
ON/OFF MUTING
CLIP PROT PWR SIG
THERMAL MUTING
Not Illuminated
Full Brightness
KEY
Flashing
NO SIGNAL
STEADY CLIPPING
OCCASIONAL CLIPPING
NORMAL SIGNAL
CLIP PROT PWR SIG
CLIP PROT PWR SIG
CLIP PROT PWR SIG CLIP PROT PWR SIG
CLIP PROT PWR SIG
The “PROT” indicator lights
whenever the output is muted. At
turn-on, the amplifier mutes for a
few seconds; at turn-off, it mutes
immediately and remains muted
until the power supplies have
drained.
Only the “PWR” LED is lit. This is
normal.
The “PWR” LED is lit, and the
“SIG” LED is lit or flashing. This
is normal.
The “PWR” and “SIG” LEDs are lit,
and the “CLIP” LED flashes on
occasional peaks. This is normal.
The “PWR”, “SIG”, and “CLIP” LEDs
are lit continuously. The channel is
in hard clipping, and you should
reduce power immediately to avoid
speaker damage.
The “SIG” LED is flashing, and the
“PROT” LED is lit; this indicates
that the protection circuitry is mut-
ing the output. The condition will
reset itself when conditions allow.
Figure 5: LED displays further explained.
V. OPERATIONS
When the amplifier is first turned on, the red “PROT” LED
on each channel will light for about three seconds, during
which the output relays will stay open to mute the speak-
ers. After the turn-on muting interval, the “PROT” LEDs
turn off, the green “PWR” LEDs light, and the output
relays close to enable the speaker outputs. Even during
the muting interval, the yellow “SIG” and red “CLIP” LEDs
operate normally if there is a signal present. If the “CLIP”
LED is on while the amplifier is muted, cut the gain back
immediately to avoid a full-power blast of sound when the
output relays close. (Whenever it is practical, at turn-on
you should have the attenuators all the way down to avoid
this situation.) If a channel stays muted with “PROT” lit,
or if its “SIG” or “CLIP” indicators light up when the gain
is turned all the way down, it may be defective; see the
troubleshooting segment for more information.
The “SIG” LED indicates signal levels that are -30 dB
(referenced to full output power) or higher.
When the amplifier is shut off, the amplifier should mute
both channels virtually instantaneously, with the “PROT”
indicators lit until the power supplies are discharged.