Mackie FR2500 User Manual

FR SERIES AMPLIFIERS

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.

Keep these ventilation slots free from any obstruc-

tions, so the air may flow freely and cool down the power 
transistors.

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.

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.

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.