User guide

Page 9
SMA/ SBA SERIES
INSTALLATION
POWER REQUIREMENTS
Power consumption for your model of the SMA 250/ SBA 250P amplifier is indicated on the rear panel for
maximum output.
Ensure that your mains voltage is the same as the rear panel mains voltage marker (± 10%).
MOUNTING
Your amplifier is designed for standard 19” rack mounting and occupies 2 EIA rack units (3.5”). The mounting
centres are:
Vertical: 3” (76.0 mm) Horizontal: 18.2” (461.8 mm) to 18.7” (470.8 mm)
The slots in the mounting flange will accept bolt diameters up to 1/4” (6.35mm).
We recommend that you provide additional support for the amplifier, especially if road use is planned, as the
weight could bend some rack frames. This support can be provided by secure shelving, support rails or a rear
rack mounting strip to match up with the rear rack mount ears provided on your amplifier.
COOLING
Your new SMA/SBA amplifier is cooled by an axial fan which draws cool air from the front of the amplifier and
expels the heated air out the rear of the amplifier. These amplifiers offer two speed fans that is In OFF condition
Initially and switching to full speed when the internal heat-sink temperature exceeds 60∞ C.
An unrestricted airflow into and out from the amplifier must be provided. Any restriction of the airflow will cause
heat to build up within the unit and possibly force the unit into its thermal shutdown mode.
If the amplifiers are to be operated in an environment where the airflow is restricted such as sealed racks, the
cooling should be supplemented by extra cooling fans to evacuate the heated air and aid the flow of cool air
through the unit.
INPUT WIRING
IMPORTANT: Do not directly connect pin 1 on the amplifier's input or strapping XLR, to the amplifier's chassis,
speaker ground or power ground!
WARNING: Input signal ground is not to be used as a safety ground (earth).
The XLR input to your amplifier is a balanced 3-pin configuration and requires all three pins to be connected.
Only high quality twin-core shielded cable should be used.
When wiring for a balanced source, the connector going to the input of your amplifier should be wired as
follows:
Pin 1 = GROUND / SHIELD Pin 2 = HOT (In Phase - non inverting) Pin 3 = COLD (Reverse Phase - inverting)
When wiring from an unbalanced source you must ensure that pin 3 is connected to pin 1 (input ground), either
by linking the pins in the input connector or by the source equipment's output wiring.
When wiring for an unbalanced source:
Pin 1 = GROUND/SHIELD Pin 2 = HOT (in phase with the amplifier's output) Pin 3 = GROUND/SHIELD
(joins to pin 1)
NOTE: In-line XLR connectors often have a termination lug that connects directly to the chassis of the
connector.
IMPORTANT: Do not link this lug to pin 1 at the amplifier's input as it will defeat the amplifier's input grounding
scheme.