7
Setting Up and Using the Servo 120 Power Amplifier
Setting up your Servo 120 is a simple procedure which takes only a few minutes:
1. Remove all packing materials (save them in case of need for future service) and
decide where the amplifier is to be physically placed—it can be used free-standing or
mounted in a standard 19" rack, requiring only one rack space. When installed, make
sure that there is good ventilation around the entire unit (we recommend using spacer
panels, especially if multiple amplifiers are used in a rack. Before rack-mounting, use a
Philips screwdriver to remove the Servo 120’s feet and attach the included rack ears.
2. Set the rear panel Bridge switch as desired (see page 7 in this manual).
3. Make the speaker connections, using the push-spring terminal output connectors on
the rear panel. It is never a good idea to power up any amplifier that is not connected to
loudspeakers. In normal operation, any loudspeakers with a minimum impedance load of
4 ohms (that is, 4 ohms or greater) can be used; however, in Bridge mode, 8 ohm
speakers must be used. Be sure to connect the loudspeaker correctly. In normal mode,
connect them with the red (+) terminal connected to the positive input of the speaker and
the black (ground) terminal connected to the negative input of the speaker. See page 7 in
this manual for connection instructions when using the Servo 120 in Bridge mode.
4. Next, make the signal input connections, using the electronically balanced 1/4" and/or
the unbalanced RCA-type input connectors on the rear panel (if operating the Servo 120
in Bridge mode, use the left input only—see page 7 in this manual). If your mixer or
crossover network has balanced outputs, use the Servo 120’s electronically balanced
inputs (unbalanced two-conductor plugs can also be inserted into these inputs, but you’ll
get better signal quality and less outside noise and hum if you use balanced lines).
5. On the front panel of the Servo 120, turn both Channel input controls fully
counterclockwise (to their “-70” setting). Then connect the supplied 3-pin “IEC” cable to
the rear panel IEC connector and to any grounded AC socket. Because of the relay
protection circuitry built into the Servo 120, you can even plug it into the same power
strip that other audio devices (such as a mixing console) are connected to. You can then
turn on all devices at once with the single power strip on-off switch, with no danger of
damaging connected speakers by generating “thumps.”
6. Press the front panel Speaker on/off switch (so that it is in, in its “down” position) and
then press the front panel Power switch in order to turn on the Servo 120. The Power
LED will light and the Protection LED will go on. After approximately five seconds, the
Protection LED will go off and the Speaker LED (in the Speaker on/off switch) will light
instead (you’ll hear a click when this occurs).
7. Apply an input signal to the Servo 120 at or about +4 dBu (if sending signal from a
mixer, drive the output meters at approximately 0 vu). While the input signal is present,
slowly raise the Channel Input controls until the desired sound level is achieved.
The five-segment LED meters next to each Channel input control will show you the
continuous power output of the Servo 120 as signal is being passed. For the best signal-
to-noise ratio, the Servo 120 should normally be run with the Channel Input controls at or
near maximum (fully clockwise, at the “0 dB” position) and the right-most (0 dB / 100%)
segment should light occasionally (but not frequently) during peak levels. If you are
using a mixer that has a master output level control (sometimes called “control room
level”), use it to attenuate the signal as necessary to achieve the desired speaker level.
8. You can monitor the input signal in privacy by connecting a pair of headphones to the
front panel headphone jack and pressing the Speaker on/off switch so that it is out (in its
“up” position), at which time the Speaker LED will go off.
WARNING: Because the Servo 120 is capable of generating extremely high
headphone signal levels, always start with the Channel Input knobs turned down
and then slowly raise them to the desired level.
If you encounter difficulty with any aspect of setting up or using your Servo 120, you can
call Samson Technical Support (1-800-372-6766) between 9 AM and 5 PM EST.
Bridge switch
Output connectors
Input connectors
Protection LED
Headphone jack and
Speaker on/off switch
Channel Input control
Five-segment LED meters
BRIDGE
OFF
ON
+RIGHT
GROUND
LEFT+
MONO (8
Ω
)
-
+
BALANCE
RIGHT
LEFT
M0N0
BALANCE
LEVEL
-35
-40
-45
-50
-55
-60
-6
5
-70
0dB
-5
-10
-15
-20
-25
-30
PROTECTION
100%
70
50
30
10
0dB
-3
-6
-10
-20
SPEAKER
