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SP-20AB MANUAL
Descriptions of Controls
Front Panel
INPUT LEVEL:
The Input Level control can be
adjusted for maximum signal to noise and
minimum clipping. The Input Level control is
stereo - it affects both left and right channels
simultaneously and affects all outputs.
SIGNAL PRESENT LIGHTS:
These yellow
LED’s turn on whenever a signal exceeding
125 millivolts RMS (40 dB below full power) is
present at the SP-20AB’s input jack. They will
increase in brightness as the signal strength
in creases. This feature is very useful as a
clue to where the fault may lie if the expected
program is not heard at the outputs.
OVERLOAD LIGHTS:
These LED’s glow red to
indicate an overload in the SP-20AB. If the
LED lights up, either the drive level to the
unit should be re duced, or the setting of the
Input Level control should be reduced until
the LED remains off. The lights turn on when
the signal level at either output is within 2 to
3dB of clipping. Once triggered, the lights will
stay lit for a mini mum of 50 milliseconds so
they can be easily seen, even if the actual
dura tion of the overload is much shorter.
HEADPHONE JACK / HEADPHONE VOLUME:
Any type of headphones wired with a
standard 1/4” stereo phone plug may be
used successfully. Note that the headphone
volume may be adjusted without affecting
the speaker level or the level of any other
headphones connected through HR-2
Remote Stations.
SPEAKERS BUTTON:
Depressing this button
turns on the speakers connected to the
SPEAKER banana jacks on the rear panel.
This provides an easy way to mute the sound
without changing the volume setting.
POWER LIGHT:
Glows red when unit is
receiving power and the ON-OFF SWITCH
is in the ON position.
Rear Panel
ON-OFF SWITCH:
This switch turns the SP-
20AB on and off. For convenience, it is
recommended that the SP-20AB and any
other rack-mount equipment be powered
through a switchable outlet box, such as
the Furman Sound PL-8 or PL-PLUS Power
Conditioner and Light Module. The PL-8
provides an easy way to power up the
whole rack with one front-panel switch, and
provides dis creet illumination on dark stages
and studios as well. If you do use a switcha-
ble outlet box, leave the SP-20AB’s on-off
switch in the ON position at all times.
GROUND LIFT SWITCH:
In many installations,
hum-causing ground loops are formed by
the common connection of various pieces of
equipment to the pow er line ground, and by
3
1
2
3
4 6
8
9
10
0
5
7
INPUT LEVEL
LEFT
20 WATTS / CHANNEL
RIGH
T
OVERLOAD
SPEAKER
S
SIGNAL
MONO
STEREO
L
BRIDGED
R
USE FOR BRIDGED
MODEL SP-20A
SATELLITE / REMOTE
VOLUME
LEFT / MONO INPUT
SPEAKERS
ON
RIGHT INPUT
OFF
1
2
3
4 6
8
9
10
0
5
7
120 VAC
60 Hz
130 Watts
HEAD
PWR
ON
STEREO AMPLIFIER
PHONE
OFF
LIFT
GND
LEFT RIGHT
SPEAKERS
MONO
STEREO
BRIDGED
USE FOR BRIDGED
SATELLITE / REMOTE
LEFT / MONO INPUT
RIGHT INPUT
120 VAC
60 Hz
130 Watts
ON OFF
LIFT
GND