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
3
PA250A Power Amplifier Block Diagram
Technical Specifications
Dimensions: 19" wide x 3.5" high x 12.5"deep (482mm wide x 88mm high x 317.5mm deep) Color: Black
Frequency Response:
20Hz-20KHz + 3dB (any input to any output)
Mixing
And
Control
Section
“TEL”
and 600
W
Inputs Mute
the Aux I nput.
The mute
function may
be defeated by
changing an
internal circuit
board jumper.
Speaker Level Outputs: Screw terminals. 250W RMS @ 4
W
, 25V, 70.7V. 200W RMS @ 4
W
output into 8
W
load
Total Harmonic Distortion: < 0.3% at 1kHz at rated power (4
W
direct output)
Hum and Noise: > 90dB below rated output (unweighted)
Weight: 18LBS. (8.2KGS)
Shipping Weight: 20LBS. (9.1KGS)
Power
Amplifier
250W RMS
“TEL” Input
& 600
W
Input
Gain
Control
SPEAKER LEVEL OUTPUTS
TEL-PAGE Input: Removable Phoenix Connector. 50mV @ 600
W
balanced (required for full rated output power)
AUX Input: Parallel RCA Connectors, 500mV @ 10k
W
unbalanced (required for full rated output power)
Amplifier Muting-Priority Scheme
The amplifier includes unique voice-activated (VOX) ducking/muting
circuitry. When a page is made into the
“TEL” input or 600
W
line level
input, music that is feeding the Aux input will duck in volume (not be
completely muted). If the incoming page is strong enough in level, the
music volume will be completely muted. When the page has been
completed, the volume of the music will return to its normal level. The
muting circuit can be defeated by a qualified technician, by removing
the chassis cover and repositioning the X2 MUTE jumper that is
located behind the recessed gain control on the input circuit board.
Parallel
RCA Jacks
(Pin +, Sleeve )
+ TEL -
GND
+ 600
W
-
Note: Both the TEL-PAGE input and the 600
W
input
are 600
W
balanced transf ormer isolated line level
inputs, but t he 600
W
input has lower input sensitivity
than the TEL-PAGE input. In ot her words, the TEL-
PAGE input is a
“hotter” input so it takes less input
signal to drive the amplifier t o full power when using
the TEL-PAGE input.
Red Peak LED Note: If the red peak LED flashes, it indicates the peaks are approaching
full power. A steady bright red glow could indicat e that the amplifier is being
over-driven, has oscillat ion in the system, or has a shorted speaker line.
Peak LED (Red): If the red peak LED flashes, it indicates the peaks are approaching full power. A steady bright
red glow could indicate that the amplifier is being over-driven, there is sub-sonic or ultra-sonic
oscillation in the system, or the amplifier is loaded with a shorted speaker line.
“Power On” LED (Green): Lights when the power amplifier is switched on.
600
W
Input: Removable Phoenix Connector. 500mV @ 600
W
balanced (required for full rated output power)
AC Supply Voltage: 115/230VAC 60Hz + 10%, Power Consumption: 480W @ Rated Power
Jumper X2 in Mute-Active
Position as set at the Factory
Jumper X2 shown in
Mute-Defeated Position
4
W
GND
25V
70.7V
C
AUX
Input
_
Paging Horn Protection Low-Cut Filter
The PA250A includes a low-cut filter (also called a
“trumpet protect” filter) that is
not activated when the amplifier is shipped from the factory. When the amplifier is to be
used to power paging horns that can be damaged by the low frequency energy that is often
present in paging/music signals, we recommend that a qualified technician activate the low-
cut filter by removing the chassis cover and cutting the red jumper that is located directly
behind the recessed gain control on the input circuit board. The red jumper is labeled as
shown in the picture to the right. The low-cut filter has a 3dB down point at 400 Hz.
A low-cut filter may be activated by cutting a
circuit board jumper. Act ivating the low-cut
filter is recommended when using t he PA250A
to power paging horns (for trumpet prot ection).
External Circuit Breaker: 5A Internal Fuse: 5X20mm 5A Slow Blow