3
REAR PANEL
FU
SE
FU
SE
O
CAUTION:
Risk of fire -
replace fuse only
with same type
6 A 250 V
120V
~
60Hz
900 Watts
MPA250
BIAMP SYSTEMS
an affiliate of Rauland Borg Corp.
MADE IN U.S.A.
CAUTION
RISK OF ELECTRICAL SHOCK.
DO NOT OPEN.
Class 2 Wiring
xfmr output
direct
output
GND
4
Ω
XFMR
INPUT
COM
OUT
25V
CT
25V
70V
8
Ω
signal / peak
temp / fault
level
input
BAL
HPF
UNBAL
OFF
775mV
300mV
52SJ
UL
R
LISTED
C
US
Input:
This plug-in barrier strip provides the line-level input to the amplifier. For unbalanced input, wire high (+) and ground (
). For
balanced input, wire high (+), low (-), and ground (
).
NOTE:
The UNBAL / BAL switch must be in the appropriate position (see below).
Level:
This screw-driver adjustable control determines the level of input signals allowed into the amplifier. Level provides a gain range
from 'off' (min.) to 'unity' (max.). The Level control is factory set for -20dB of gain, which will produce maximum output power with input
signal peaks of +20dBu. For best performance, first adjust the source signals for optimum (maximum) levels, then adjust the amplifier
Level control for the desired volume.
Signal / Peak Indicator:
This 2-color LED indicates the signal level for the amplifier. When the LED is green, the amplifier has signal
(above -30dB). When the LED is red, the amplifier signal is clipping (max. power).
CAUTION:
Signal levels should be adjusted to avoid
clipping. Clipping can cause severe distortion, over-temperature conditions, and even loudspeaker damage.
NOTE:
Signal / Peak
indicators will turn off during Temp / Fault conditions (see Temp / Fault Indicators below).
This indicator also appears on the front panel.
Temp / Fault Indicator:
This red LED indicates over-temperature and output fault conditions for the amplifier. When the LED remains lit,
the amplifier has an over-temperature condition. When the LED is flashing, the amplifier has an output fault condition. Either condition will
temporarily de-activate the amplifier, causing the Signal / Peak LED to turn off as well. The amplifier will attempt to self-reset once the
over-temperature or output fault condition is resolved. This indicator also appears on the front panel.
CAUTION:
The MPA250 is cooled
by a variable speed fan, which exhausts warm air from the left side panel. To allow proper ventilation, an un-obstructed clearance of at
least 0.75" must be maintained along the left side panel of the MPA250.
HPF Switch:
This DIP switch provides a High-Pass Filter for the amplifier input. The High-Pass Filter is used to eliminate unnecessary
lower frequencies (12dB/octave @ 125Hz) for speech and distributed speaker applications. From the factory, the High-Pass Filter is
enabled (switch down). To disable the High-Pass Filter, move the switch to the up position.
CAUTION:
To avoid output fault conditions,
the High-Pass Filter must be enabled when driving 25/70 Volt speaker systems (see Output below). Also, any other system equalization
affecting frequencies below 125 Hz should remain flat or be used as cut-only.
775mV / 300mV Switch:
This DIP switch selects 0.775Vrms (-0dBu) or 0.3Vrms (-8dBu) as input sensitivity for the amplifier. From the
factory, input sensitivity is set for 775mV (switch up). Use the 775mV setting for 'professional' line-level input signals (such as from an
audio mixer or processor), or use the 300mV setting for 'consumer' line-level signals (such as from a CD player or tape deck).
UNBAL / BAL Switch:
This DIP switch selects unbalanced or balanced input connection. From the factory, input connection is set for
UNBAL (switch up). Use UNBAL for 2-conductor connections, and use BAL for 3-wire connections (see Input above).
Output:
These screw terminals provide the speaker outputs from the amplifier. From the factory, a jumper wire is installed from the 4
Ω
terminal (direct output) to the XFMR INPUT terminal. For transformer (xfmr) output, connect speaker negative to the COM OUT terminal,
and connect speaker positive to the appropriate transformer output terminal (8
Ω
for an 8 ohm speaker load; 70V for a 70 Volt distributed
speaker system; 25V for a 25 Volt distributed speaker system). For 'balanced' 25V speaker systems, connections are the same as above,
plus a ground connection (center-tap) made to the 25V CT terminal. For direct output from the amplifier, first remove the factory installed
jumper wire, then connect speaker negative to the GND terminal, and connect speaker positive to the 4
Ω
terminal.
AC Power Entrance:
The switch applies AC power to the unit. The receptacle accepts the detachable AC Power Cord. The AC Power
Cord is for connection to three-prong grounded AC outlets.
CAUTION:
Do not remove or defeat the ground prong on the AC Power Cord,
as this constitutes a shock hazard.
Fuse:
Replace Fuse with same type and value only (6 A 250 V).
NOTE:
If the Fuse continues to blow, the amplifier may require service.
