Martin Audio Protection Features, Martin Audio - MA200Q Amplifier, English

CONTENTS

< > PRINT

8.2Powering up – Soft start

When you power up the amplifier it takes a couple of seconds to self-check. This is known as the "soft-start" or "slow-start" sequence. The fans then blow at high speed before going into "idle" and the four bottom green LED’s illuminate to show the amplifier is operational.

8.3Input attenuators

The four input level attenuators on the front panel adjust the signal level for their respective amplifier channel’s in all modes of operation. They are calibrated in dB's to help the setting up of active loudspeaker systems.

In bridged mode, both level attenuators must be in the same position, so that the loudspeaker load will be shared equally between the channels.

8.4	Indicators
	PROTECT		PROTECT
		CLIP		CLIP
		-40dB		-40dB
		ON		ON
	CH.A	CH.B	CH.C	CH.D
	-12 -10 -7	-12 -10 -7	-12 -10 -7	-12 -10 -7
	-16	-5 -16	-5 -16	-5 -16	-5
	-20	-3 -20	-3 -20	-3	-3
	-40	-1 -40	-1 -40	-1 -40	-1
	-80 dB 0	-80 dB 0	-80 dB 0	-8 0 dB 0
		MA200Q

The yellow LED's on the front panel indicate if any protection circuits are activated. These are described on page 14.

The Clip/limit LED's indicates when the amplifier output is clipping or limiting. It has two different indication states:

•When the clip limiter is engaged it has a short time constant and illuminates briefly.

•When the clip limiter is not engaged it has an increased time constant and illuminates for a longer period.

The “- 40dB” LED’s illuminate when the output signal is greater than -40dB (with 0dB referenced to full output power). These LED’s also act as signal present indicators.

The four bottom green “ON” LED’s indicate when the power supply is operating normaly and the output circuits are receiving the correct rail voltage.

9 PROTECTION FEATURES

Each Martin Audio MA series amplifier has many advanced protection features, that will protect both the amplifier and the loudspeakers connected to it, should a fault condition arise. Under normal use these features are inaudible. All protection circuits operate independently.

9.1Output Limiter

An output limiter is included to avoid amplifier clipping. When an amplifier is severely overdriven, its output waveform is clipped (its peaks are squared off) – reducing the crest factor. In extreme cases, the waveform can approach that of a square wave. An amplifier is normally capable of producing far more power under these conditions than its normal undistorted rated output power.

The limiter works by monitoring the output and comparing the distortion produced between the input and output of the amplifier. If the distortion exceeds 1%THD for any reason (voltage or current clipping), the

14

Martin Audio – MA200Q Amplifier

ENGLISH