QSC Audio MX 1000a, MX2000a IV. Outputs, Operations, Controls and Displays, AC Power, LED Color

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:

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.

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

ON/OFF MUTING

PWR SIG CLIP PROT

NO SIGNAL

PWR SIG CLIP PROT

NORMAL SIGNAL

PWR SIG CLIP PROT

OCCASIONAL CLIPPING

PWR SIG CLIP PROT

STEADY CLIPPING

PWR SIG CLIP PROT

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.

amperes during “normal” operation, but peak current draw under heavy usage can be much higher.

Figure 5: LED displays further explained.

THERMAL MUTING

PWR SIG	CLIP PROT	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.

KEY

Not Illuminated

Flashing

Full Brightness

6