Design Features - Martin Audio MA1.3 User Manual

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CONTENTS
This circuit is inaudible in normal use, however it can be turned off.
If the VHF protection is required to be turned off i.e. for studio monitors,
please consult your supplier, as this is a non-user adjustment.
Short circuit protection
All MARTIN AUDIO MA Series amplifiers are completely short circuit
protected. The protection circuit permits very high peak currents, but still
holds the output devices within their safe operating area. If a short circuit is
maintained, the channel affected will eventually go into a thermal protect
cycle until the short circuit is removed.
AC mains voltage protection
If the AC mains voltage is outside the operational window (over or under
voltage), the power supply will automatically shut down. When the mains
voltage is above the minimum start voltage and below its maximum
operating voltage the amplifier will restart.
It takes a couple of seconds to self check (this is known as the "soft start"
or "slow start" sequence), the gain will gradually be increased back to the
previous set level and the fans will blow at high speed before going into
"idle". The two green "ON" LED's then indicate that the power supply and
output stage is operating correctly.
D.C. protection
There are two types of DC protection:
• Fuses on the supply branches of each channel.
• A DC crowbar protection circuit that shorts the output if more than 10 volts
is detected on the outputs. Both these circuits come into effect once a DC
level is detected.
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Cooling
MARTIN AUDIO MA Series amplifiers run very cool due to a patented heat
exchanger. The bi-polar output devices are mounted directly onto a copper
heat sink thereby avoiding thermal losses normally found when using mica
washers. The heat sink is mounted horizontally in front of a pressure
chamber and the air flow is constant along the whole heat sink. When cool
air hits the geometric fins of the heatsink, turbulence is produced thereby
enabling efficient cooling. (In a conventional tunnel design the end of the
heat sink away from the fan invariably gets hotter than that directly in front
of the fan).
Light weight
The MA1.3 switch mode amplifier has a very good power to weight ratio.
This is achieved not only by the design of the power supply and heatsink
but also by the use of an alloy chassis making rear rack supports
unnecessary in most applications.
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DESIGN FEATURES

Martin Audio – MA1.3 Power Amplifier
16
GUIDES