Instruction Sheet
IS-MA60/125/250
Issued: 3-6-18
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
Note: A push switch is provided on channels 1 through 5 that turns on the aux input jacks and at the same time
pads the XLR and screw terminal inputs for that channel so they can be used as low impedance balanced line level
inputs.
With the switch in the “AUX” position, use either the aux input jacks, or the XLR/screw terminal low
impedance line level inputs.
Do not use both at the same time.
When using the XLR jacks or screw terminals as
line inputs, defeat the phantom power for that input channel.
MIC LEVEL INPUT CONNECTIONS
The amplifier includes low-impedance balanced microphone inputs. 16VDC Phantom
Power is available at microphone inputs 1-5. The amplifier is shipped from the factory
with internal Phantom Power jumpers set “ON” for Channel 1-5. The Phantom power
for each microphone channel may be defeated by first unplugging the power cord , and
then removing the amplifier chassis cover and changing the jumper position for that
channel to “OFF” (Channel-1: jumper JP1, Channel-2: jumper JP2, Channel-3: jumper
JP3, Channel-4: jumper JP4, and Channel-5: jumper JP5). The jumpers are located
on the circuit board that includes the input connectors. See the picture to the right
which shows JP2 (for Channel-2) and JP4 (for Channel-4).
JP2
RCA Phono Plug Connection
Pin Sleeve
Sleeve:
Shield
Pin:
Signal
GENERAL WIRING AND INSTALLATION GUIDELINES
DO NOT
run microphone cables near AC power wires, data cables, telephone cables, or speaker wiring to avoid
picking up extraneous signals in the sound system.
DO NOT
run speaker output cables near data cables, telephone cables, or other low voltage wiring that could pick
up the signal from the higher level speaker cables.
DO NOT
run high impedance unbalanced wiring more than 20' to avoid picking up noise and affecting the frequency
response of the sound system.
DO
use shielded cable for all microphone and line level cables (except the balanced 600 ohm input line from a
telephone system may be twisted pair cable).
DO
make sure that all speakers are wired in phase with each other .
DO
make sure there are no short circuits on the loudspeaker lines before connecting them to the amplifier output .
JP4
2
3
1
GND
_
+
+
GND
_
TO INPUT
CHANNEL
MICROPHONE CHANNEL INTERNAL WIRING
LINE LEVEL “AUX” INPUT CONNECTIONS
The amplifier includes high-impedance unbalanced auxiliary inputs which may be used for connecting the output of
an AMFM tuner, CD player, cassette deck, or other music program source. A push switch is provided on Channels
1 through 5 that selects the aux input jacks while switching the XLR and screw terminal inputs for that same channel
to low impedance line level inputs. Use the aux input jacks
or
the line level XLR/screw terminal inputs but
do not
use both at the same time
. Two (2) RCA-phono connectors are provided for each aux input so stereo input cables
can be connected. The stereo input signal is converted internally to a mono signal . Mono inputs need only use one
or the other of the RCA-phono connectors.
GROUND LOOPS
Any time two (2) pieces of equipment (that both are powered by grounded AC plugs are
connected by an unbalanced RCA to RCA cable, a ground loop is created. In some instances, this does not cause
a problem.
In other cases this causes a “hum” or “buzz” that can be heard in the system’s speakers . This can be
corrected using industry standard grounding techniques , but another simple way to eliminate the ground loop is to
replace the RCA to RCA cord with a Lowell TSM-ISO isolation transformer that is sold separately .