Mackie HD 1801 9. SIG/LIMIT LED, 10. THERMAL LED

HD1801	HD1801
	18 -INCH HIGH DEFINITION POWERED SUBWOOFER

INPUTS

AB

3

OUTPUTS

A	FULL RANGE	B
	5			SETTINGS	10
				THERMAL
				POWER
				LIGHT ON
A		B	7	SIG/ LIMIT		9
	HIGH PASS
				POLARITY
	4		6	INVERT
				-6dB	+6dB
					LEVEL

8

9. SIG/LIMIT LED

This bi-color LED illuminates green whenever there is a signal present at the main inputs. It senses the signal just after the level control, so adjustments to the level control will affect the sig/limit indicator.

The HD1801 has a built-in limiter that helps to prevent the amplifier outputs from clipping or overdriving the transducer. The sig/limit indicator lights in yellow when the limiter is activated. It’s okay for it to blink yellow occasionally, but if it blinks frequently or lights continuously, turn down the input level until it only blinks occasionally.

Excessive limiting may lead to

overheating, which in turn trips the thermal

protect circuitry and interrupts the performance. See ‘Thermal Considerations’ on

page 14 for more information.

10. THERMAL LED

The HD1801 is equipped with a thermal protection circuit that monitors the internal temperature of the amplifier and heatsink. If the temperature begins to exceed a safe operating level, this indicator lights and the amplifier output is limited to allow the amplifier to cool. If the amplifier becomes excessively hot, the amp is muted until it cools, then the HD1801 returns to normal operation.

When the HD1801 is in thermal protect mode, the power LED (2) will remain lit, indicating that the unit is still powered on despite the lack of output. If POWER LIGHT ON (7) is engaged, the front panel power LED will go out when in thermal protect mode.

Activation of the thermal protection circuit

is an indication that you should take steps to avoid continued thermal problems. See “Thermal Considerations” on page 14.

10 HD1801