12
HEATSINK
THERMAL
TRANSFORMER
120V
120V
240V
HIGH VOLTAGE POWER LINE
EARTH
GROUND
(NEUTRAL)
PRIMARY
WINDING
SECONDARY
WINDING
240V CENTER-TAPPED SECONDARY
PEAK
LOW CUT
AC POWER
CONSIDERATIONS
Be sure the SRM450 is plugged into an
outlet that is able to supply the correct volt-
age specified for your model. If the voltage
should drop below 97% of the specified line
voltage, the built-in amplifiers will no
longer be able to supply rated power. (They
will continue to operate down to 75% of
the rated line voltage, but won’t reach full
power, resulting in lower headroom).
Under maximum S.P.L. conditions,
where musical peaks are clipping, the
SRM450 120V model draws 2.5 amps on
average (1.3 amps for the 240V model). Un-
der normal conditions, the current draw is
below 1 amp.
We recommend that a stiff (robust) sup-
ply of AC power be used because the
amplifiers place high current demands on
the AC line. The more power that is avail-
able on the line, the louder the speakers will
play and the more peak output power will
be available for cleaner, punchier bass. A
suspected problem of “poor bass perfor-
mance” is often caused by a weak AC
supply to the amplifiers.
AC Power Distribution
A 240VAC center-tapped service en-
trance transformer serves the majority of
AC outlets encountered in homes and clubs
(in the U.S.). This provides two phases of
AC power on either side of the center tap,
at 120V each.
If lighting is used in a show, it is prefer-
able to power the lights from one leg of the
service, and power the audio equipment
from the other leg. This will help minimize
noise from the lights coupling into the au-
dio (particularly if SCRs, or light-dimmer
switches, are used).
THERMAL
CONSIDERATIONS
The amplifiers inside
the SRM450 are con-
vection cooled by a
large heatsink. For ef-
ficient cooling, it is
important to allow at least six inches of
free space behind the SRM450.
If you use the SRM450
on its side for stage
monitor applications,
we highly recom-
mended that you engage
the rear panel
LOW CUT
switch. This will
allow more power for useful monitor fre-
quencies, while reducing the possibility of
overheating.
If the ambient temperature in the
room is high, it could cause the amplifi-
ers to overheat. In this case, you should try
aiming a fan at the heatsink to increase the
air flow through the fins.
During a performance, don’t have it
cranked so high that the rear panel
PEAK
LED is blinking frequently or lighting con-
tinuously. You should turn down the
LEVEL
control a notch or two to avoid
overheating the amplifiers or your neigh-
bors.
If the amplifiers do overheat, a built-in
thermal switch will activate, placing the
amplifiers into standby. When the amplifi-
ers have cooled down to a safe operating
temperature, the thermal switch will reset
and the SRM450 will resume normal opera-
tion.
