QSC MX-1000a Bedienungsanleitung PDF herunterladen (Seite 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.

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