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MINUSPLUSPLUSMINUS
RIGHT LEFT
(-) (+)
NOT USED
RBUS
L+R BUS
LBUS
NO VOL
USE VOL
JUMPER DESCRIPTION
The jumper modules are used in configuring each channel. Each jumper terminal location
is conveniently labeled as to the source it can be configured to provide.
R BUS - Along with being the right channel input, it is used as the input to the right bus
and the right source for the ‘L+R BUS’. Because it is a BUS input, any signal input here
would appear at the ‘R BUS’ jumper terminal for both of the ST55.2’s jumper modules.
L+R BUS - Installing a jumper plug at this terminal on either of the two internal jumper modules selects the
combined signal being carried by both the left and right inputs. If the left bus and right bus are being used to carry
stereo right and left channels, a jumper plug installed at the ‘L+R BUS’ location will provide a true L+R mono
output.
L BUS - Along with being the left channel input, it is used as the input to the left bus and the left source for the
‘L+R BUS’. Because it is a BUS input, any signal input here will appear at the ‘L BUS’ jumper terminal for both of
the ST55.2’s jumper modules.
NO VOL - If volume control is desired only from the source, or if outputs are being combined to obtain higher
power, the jumper plug should be installed at the ‘NO VOL’ location.
USE VOL - If volume control is desired at the amplifier, beyond that provided at the source, a shorting plug is
installed at the ‘USE VOL’ location. The ‘USE VOL’ setting SHOULD NOT be used when channels are bridged or
combined.
Invert Jumper module - This is a single jumper module that is set apart, up and to the right from the channel
jumper modules on the circuit board. It provides a special function, when the jumper is set on the ‘-L’ pins, the left
bus signal feeding the left channel will be inverted.
Note: A jumper MUST be installed at L BUS, R BUS, or L+R BUS, AND a jumper MUST be installed at NO VOL
or USE VOL for the amplifier to operate.
MONO APPLICATION (MEDIUM CURRENT)
The ST55.2’s two output channels may be paralleled (mono) to combine the left and right channels output current.
This feature allows the amplifier to double its apparent output current. To use, place the source group jumper for
both channels on the ‘L BUS’ jumper terminal. Place the volume group jumper for both channels on the ‘NO VOL’
jumper terminal.
The speaker output terminals on the ST55.2’s rear panel
must be paralleled in order to complete the setup. Simply
connect the (+) terminals for both channels together using
a jumper wire (not supplied with the amplifier). Finally,
connect the speaker cables from the left channels (+) and
(-) terminals to the speakers. Input your source signal into
the left channel input. The instructions show the use of the
left channel. You may also use the right channel if you
desire, just follow the above instructions using the right
channel. You may also use the L+R BUS to send a mono
signal out of the amplifier derived from the left and right
channels. See the Bus Inputs below:
BUS INPUT
LEFT
RIGHT
R
L
From Left Output
of Preamplifier
NOT USED