MACKIE FRS1700 - Manual (Page 8)

8
FRS Series Amplifiers
FRS Series Amplifiers
OL
-3
-6
-9
-20
SIG
OL
-3
-6
-9
-20
SIG
2
O O MAX MAX O O
1
FRS • 2800
FAST RECOVERY POWER AMPLIFIER
Front Panel Features
1. Power
Use this rocker-style 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 at the top of the switch will light
when the power switch is on.
2. Ventilation
Keep these ventilation slots free from any
obstructions, so the air may flow freely and cool
down the power transistors.
3. Meters
OL is short for “overload.” These indicate when the
output of the amplifier has reached the maximum and
is right on the edge of clipping. Clipping is very bad for
speakers and should be avoided to prevent damage.
It is okay if the OL LEDs blink occasionally. It means
that the transient peaks of the music are just hitting
the full output of the amplifier. However, if the OL LED
is blinking frequently or continuously, turn down the
source signal (i.e., the mixer’s master faders) or the
amplifier’s level controls.
The meters indicate the signals are below maximum
output power by: –3 dB, –6 dB, –9 dB, and –20 dB.
SIG is short for “signal present.” These LEDs indicate
when a signal is present after the level controls, at the
output stage of the power amplifier. If the level controls
are turned all the way down (fully counterclockwise),
these indicators will not light.
4. 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 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
connected directly to the amplifier without a
preamplifier or mixer.
The amplifiers are designed so that a +3.4 dBu
(1.15 Vrms) input signal drives the amplifier to full
power into 4 ohms:
FRS•1700 = 540 watts per channel into 4 ohms
FRS•2800 = 850 watts per channel into 4 ohms
This equates to a gain of 33 dB and 35 dB respectively.
After you have set the levels for the mixer
(or other signal source), adjust the level controls
on the amplifier 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 2 level
control down, and just use the channel 1 control.
1 2 3 4 4