MACKIE FR1400 - Manual (Page 8)

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FR SERIES AMPLIFIERS
FR SERIES AMPLIFIERS
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Front Panel Features
1. POWER
Use this rocker switch to turn the unit on or off. This
connects/disconnects the AC power to the AC power
transformer.
The amplifier is on when the top of the switch is
pressed in. It is off when the bottom of the switch is
pressed in.
The Power On LED above the switch will light when
the power switch is on.
. VENTILATION
Keep these ventilation slots free from any obstruc-
tions, so the air may flow freely and cool down the power
transistors.
. OL LEDs
This is short for “overload.” These red LEDs indicate
when the output of the amplifier has reached the maxi-
mum, and is right on the edge of clipping. Clipping is
bad for speakers and should be avoided.
It is okay if the OL LED blinks occasionally. It means
that the transient peaks of the music are just hitting the
full output of the amplifier.
However, if the OL (overload) LED is blinking fre-
quently or continuously, turn down the source signal
(i.e., the mixer’s master faders) or the amplifier’s Level
controls.
4. SIG LEDs
This is short for “signal present.” These green LEDs
indicate when a signal is present after the Level con-
trols, at the output stage of the power amplifier. If the
Level controls are turned all the way down (fully coun-
terclockwise), these indicators will not light.
5. LEVEL CONTROLS
These two knobs control the levels of Channels 1 and
2. The knobs are detented to make it easy to set both
controls to the same level. Usually, these controls are
set all the way up.
You might turn them down slightly if you have high-
efficiency speakers. Also, you could use them to control
the level of line-level sources such as a CD player con-
nected directly to the amplifier without a preamplifier
or mixer.
The amplifiers are designed so that a +3.4 dBu (1.15V
rms) input signal drives the amplifier to full power into
4 ohms:
FR•800 = 300 watts per channel into 4 ohms
FR•1400 = 450 watts per channel into 4 ohms
FR•2500 = 750 watts per channel into 4 ohms
This equates to a gain of about 30 dB (30 dB, 32 dB,
and 34 dB respectively).
After you have set the levels for the mixer (or other
signal source), adjust the Level controls on the ampli-
fier as the final adjustment to set the overall volume for
the system.
In stereo and mono mode, use both level controls
to control the levels going to each speaker. In bridged
mono mode, turn the channel 1 level control down, and
just use the channel 2 control.
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