Channel A output is connected as in the normal stereo mode. By having
channel A and B operating in opposite polarity, the energy storage in the
power supply is more efficient. This means that the amplifier can deliver up
to 10% more power than in tandem mono mode. This is significant for
signals below 100Hz (sub bass etc.).
7
OPERATION
7.1
Operation precautions
•
Make sure that the power switch is off before making any input or
output connections or operating the switches on rear panel. See pages
6-12 about installation.
• Make sure that the AC mains is correct and the same as that printed on
the rear panel of the amplifier. See pages 6-8 about operating voltage
and power consumption.
• Make sure that the switches on the rear panel for operation modes,
clip limiters and the MLS™ switches are in the correct position.
See pages 13 and 14 about operation modes, page 16 about clip
limiters and page 12 for the MLS switches.
• It is always a good idea to turn down the gain controls during power up
as this prevents speaker damage, especially if there is a high level
signal at the input.
7.2
Powering 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 two bottom green LED's
illuminate to show the amplifier is operational.
7.3
Input attenuators
The two input level attenuators on the front panel adjust the signal level for
their respective amplifier channel in all modes. They are calibrated in dB to
assist setting up active loudspeaker systems.
In bridged mode, both controls must be in the same position, so that the
speaker load will be shared equally between the channels.
7.4
Gain switch
The gain switch located on the rear panel is for changing the input
sensitivity of the amplifier. Most professional mixing consoles operate at a
nominal level of +4dBu. Therefore, use the 32dB position (depressed
switch), to give you plenty of fader movement. On the other hand, for a
disco mixer that operates at a nominal level of 0dBu, use the upper position
setting, which has a sensitivity of 0dBu (0.775Vrms) for full power in 4
ohms.
Martin Audio – MA4.2 Power Amplifier
E
NGLISH
15
CONTENTS
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