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CHANNEL A
HIGH Z INPUT JACKS (5)
Two parallel (bridged) input jacks arc provided. This allows for one to be used as a conven¬
tional input, and the other to be used simultaneously as a "line out" (Y-cord) to connect to
another input jack on this amplifier or other amps/equipmenl. These 1/4" jacks arc not "chassis
grounded" and when used will provide a QUASI-BALANCED input capability due to a
unique "groundloop" elimination circuitry associated with the input. This feature will normally
allow "hum free" operation when relatively short 1/4" cable patches are made between the
various jacks on this amp and other jacks on equipment That share the same rack with this amp.
This QUASI-BALANCED capability is automatic, and it can not be removed from the
system's circuitry.
LOW Z INPUT (6)
A conventional three-pin female XLR input jack is provided and may he used as the channel A
input. When the (PL-2) line balancing transformer is not used, this XLR input becomes
QUASI-BALANCED with pin #3 as the positive input (connecting to the tip of the 1/4" input
jacks above), pin #2 as the negative input (connecting to the floating sleeve of the 1/4" input
jacks above), and pin #1 going to chassis ground. When the (PL-2) line-balancing transformer
is used, this XLR input becomes fully TRANSFORMER-BALANCED (Pin #3 positive, pin
#2 negative, pin #1 ground). (See tire PL-2 SELECTOR SWITCH section for details on related
settings)
PL-2 SELECTOR SWITCH (7)
This switch is to be used in conjunction with the PL-2 transformer to allow the LOW Z INPUT
to function with or without a PL-2 module being insetted in the receptacle. A similar function
was performed by using a PL-1 module inserted in the PL-2 receptacle on older amplifier
models. The "OUT' position of this switch selects the QUASI-BALANCED mode of opera¬
tion for the LOW Z INPUT (XLR jack), and routes the input signal directly to the HI Z INPUT
JACKS. In this position the HI Z INPUT JACKS may be used as outputs after the LOW Z
INPUT to allow patching this signal to another input on this amp. Normally, in this switch
position, a (PL-2) transformer is not present ("OUT') in the transformer receptacle; however,
if one were "IN" the receptacle, the LOW Z INPUT would still be QUASI-BALANCED. It
becomes TRANSFORMER BALANCED only when the IN switch position is selected. Notice
this is a very effective means to "test" for the necessity of a line-balancing transformer. The
"IN" position of the switch routes the input signals from the XLR jack, through the (PL-2) line-
balancing transformer, thus selecting the TRANSFORMER BALANCED mode of operation
for the LOW Z INPUT. In this position the HI Z INPUT JACKS may be used as outputs after
the line balancing transformer to patch the signal to another input jack on this amplifier or other
amps/equipment. If the "IN" position is selected without a (PL-2) line-balancing transformer
"IN" the receptacle, the LOW Z INPUT will be rendered inoperable.
TRANSFORMER RECEPTACLE (8)
This receptacle only receives the optional (PL-2) line-balancing transformer. When conditions
exist that demand the usage of a TRANSFORMER-BALANCED XI JR CONNECTOR at the
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