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 4ohms.
7.5
Indicators
Figure 12. Front panel indicators
The two bottom green "ON" LED's indicate when the power supply and
output stage is operating correctly.
The "-40 dB" LED's illuminate when the output signal is greater than -40dB.
0dB is referenced to full output power. These LED's also act as signal
present indicators.
The ''Clip/limit'' LED 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 remaining yellow "Protect" LED's indicate if the temperature or VHF
protection circuits are activated. These are described on page 15.
Martin Audio – MA1.3 Power Amplifier
E
NGLISH
14
CONTENTS
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GUIDES
