Violectric HPA V281 User Manual page 20

On power-up and power-down, the outputs are cut from the amplifier
circuitry by relay.
THE BALANCED LINE OUTPUTS
are located on the rear panel of the unit and are marked as "BAL OUT
LEFT" and "BAL OUT RIGHT". Gold-plated, metal-flange Neutrik XLR
connectors are implemented here.
Hint:
With a balanced-to-unbalanced adapter this connection may also be
used for unbalanced cables. PLEASE NOTE THAT IN THIS CASE PIN
3 HAS TO BE LEFT OPEN ! See also page 9 for details.
Balanced interconnection
of the XLR socket:
PIN 1
PIN 2
PIN 3
GND
in PHASE
out of PHASE
20
Unbalanced interconnection
of the XLR socket:
PIN 1
PIN 2
PIN 3
GND
Signal
OPEN !!