AMPLIFIER
OUTPUT
4W
70.7V
25V
C
GND
AMPLIFIER
OUTPUT
4W
70.7V
25V
C
GND
Instruction Sheet
IS-PA250A
Issued: 1-18-19
Lowell Manufacturing Company
100 Integram Drive
Pacific, Missouri 63069 U.S.A.
Call: 800-325-9660
Fax: 636-257-6606
Click: www.lowellmfg.com
6
Speaker System Connections
The PA250A includes a speaker output screw terminal strip. Connect a minimum 4
W
speaker line to the 4
W
output. Note: A speaker line with an impedance greater than
4
W
can safely be connected to the 4
W
output, but it will draw less than full amplifier
output power. For 25V or 70V operation, connect the low side of the speaker line to
“C” and the hot side to the 25V or 70.7V terminal. Never connect a 4
W
or 8
W
speaker
system (that has no 25V or 70V matching transformer) to the 25V or 70.7V output.
Four 8
W
Speakers
wired in Series/Parallel
8 Ohm Series/Parallel Speaker System Wiring
The Lowell PA250A power amplifier includes a direct 4
W
output that can drive a minimum 4
W
speaker line without
the use of a line matching transformer. The impedance of the speaker load must always be equal to or greater than
the 4
W
impedance of the amplifier output. For example, it is safe for the amplifier if the 4
W
output is used to drive an
8
W
load or a 16
W
load, but it is not safe for the 4
W
output to drive a 2
W
load. Overloading the amplifier output can
cause distortion, damage the amplifier, and void the manufacturer
’s warranty. It is also important to pay attention to
the power rating of the speakers used. If a 4
W
speaker is fed from the 4
W
output of an amplifier and the amplifier is
turned all the way up, the speaker will receive the amplifier
’s maximum output. A speaker must be chosen with
sufficient power handling capacity for the amplifier used. For example, if a 4
W
speaker can handle 250 watts and it
will be fed from the 4
W
output of the amplifier, an amplifier with a power output of 250 watts or less should be
chosen so that if the amplifier is turned all the way up, the speaker will be able to handle the amplifier
’s full power
output. All of the Series/Parallel configurations shown below will result in load impedances that will be safe for the
PA250A amplifier when connected as shown. Verify that the 250W maximum amplifier power when divided
between the speakers, will not exceed the power rating of the speaker chosen .
Speaker Signal Polarity
In a paging amplifier, making sure that a positive going input signal
results in a positive going speaker output signal, is often not critical.
If, however, multiple amplifiers feed speakers covering the same
area, observing correct polarity can be important so all speakers are
in phase with each other. The picture to the right shows how inputs
should be wired to result in no polarity change in the PA250A.
Balanced Inputs
RCA Phono Plug Input
+
Sleeve
_
+
Pin
TEL PAGE
Input
_
+
600
W
Input
_
+
GND
25V
70.7V
C
4
W
SPEAKER
+
_
8
W
SPEAKER
+
_
8
W
SPEAKER
+
_
8
W
SPEAKER
+
_
8
W
Eight 8
W
Speakers
wired in Series/Parallel
Result:
Each speaker receives
1/8 of the
total amplif ier power.
(1/8 of 250W RMS @ 4
W)
SPEAKER
+
_
8
W
SPEAKER
+
_
8
W
SPEAKER
+
_
8
W
SPEAKER
+
_
8
W
SPEAKER
+
_
8
W
SPEAKER
+
_
8
W
SPEAKER
+
_
8
W
SPEAKER
+
_
8
W
AMPLIFIER
OUTPUT
4W
70.7V
25V
C
GND
SPEAKER
+
_
8
W
Result:
One speaker
receives less t han the
total amplif ier power.
(200W RMS @ 8
W)
One 8
W
Speaker
AMPLIFIER
OUTPUT
4W
70.7V
25V
C
GND
SPEAKER
+
_
8
W
SPEAKER
+
_
8
W
Result:
Each speaker receives
1/2 of the
total amplif ier power.
(1/2 of 250W RMS @ 4
W)
Two 8
W
Speakers
wired in Parallel
Result:
Each speaker
Receives 1/4 of the reduced
total amplif ier power.
(¼ of 200W RMS @ 8
W)
8
W
LOAD
8
W
LO AD
4
W
LO AD
4
W
LOAD
+
_
+
_
Speaker Outputs
Direct
Out
25V/70V
Out