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 16.
8
PROTECTION FEATURES
Each MARTIN AUDIO MA Series amplifier has many advanced protection
features that will protect both the amplifier and the speakers connected to
it, should a fault condition arise. Under normal use these features are
inaudible. All protection circuits are independent.
Output 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 power output. 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 limiter reduces the input signal proportionally.
Martin Audio – MA1.6 Power Amplifier
E
NGLISH
15
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