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Operating Manual - MFA-8000 and MFA-6000 Power Amplifier
6
6. FRONT PANEL FEATURES
6.1 Power Switch
When the unit is switched on there is a 2 second
delay, during which time the PROTECT and LIMIT cir-
cuits will activate. The load is disconnected during this
power-up sequence, and the input signal is attenuated.
When turning off the amplifier, the load is removed in-
stantly, and the protect and limit LEDs will briefly turn
on as the power supply discharges.
6.2 Output Meters
Output meters display peak output voltage in dB,
referenced to full output. For example, if full output in a
given configuration is 800 watts, then “0” on the LED dis-
play means the amp is delivering the full 800 watts to the
load, “-6” would mean the output is 6dB down, or 200
watts (-6dB is half the voltage, and power = voltage
squared divided by resistance ). If the line voltage sags,
the output meters will track the drop and accurately pre-
serve the relationship between “dB below full output” and
actual clipping.
6.3 Clipping Indicator
The red CLIP LED is a true clip indicator, which
monitors the power supply as it is affected by the AC line
voltage and the speaker load. Clipping occurs when the
signal peak levels extend beyond the available power sup-
ply rails, essentially “cutting off” the crest portion of the
waveform. This produces signal distortion, and can po-
tentially damage drivers. The CLIP LED illuminates ex-
actly at the onset of clipping.
6.4 Limit Indicator
This green LED indicates that the internal elec-
tronic limiter has activated, in the form of a signal at-
tenuator. The intensity of the LED indicates the amount
of attenuation. The limiter circuit is activated by any of
the following conditions:
1. Turn-on delay for muting purposes
2. Severe output clipping
3. Excessive internal temperature (monitored at
two key points per channel)
4.
Abnormal high frequency/high amplitude signal
5. Excessive output current
6. Protect-mode muting
Off
On
0(Clip)
-3-6-9
-12-15-18-21-24-27-30
Channel One Output Level
Limit
Thrm
Protect
AC Power