ART Pro Audio Pro Channel - Mic Preamp/Compressor/EQ - Manual (Page 18)

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Rear Panel Connections
Input and Output Connections
The Pro Channel’s XLR connectors follow the AES standard: Pin 1 = Ground, Pin 2 =
Hot (+), and Pin 3 = Cold (-). The unbalanced ¼” phone jacks are the typical Tip = Hot
(+) and Sleeve = Ground.
Note: None of the Pro Channel’s circuitry is connected directly to the metal chassis.
Either the input or output ground must be connected to another portion of the signal path
in order to establish a ground reference.
Input
Only one Input jack should be used at a time. However, both inputs can be hard-wired
without having to disconnect one while using the other (i.e., if no load is placed on the
XLR input, the ¼” jack will function as if there was nothing connected to the XLR
input). However, it is still preferable to disconnect any unused cables to avoid pick up of
extraneous noise, hum, or RF interference.
Output
Both the balanced and unbalanced Output connections may be used simultaneously.
This feature is particularly handy when using the Pro Channel as a direct box for
instruments or line level signals.
XLR GND Switch
If you hear a hum when using the Pro Channel’s XLR output, a ground loop may be the
problem. To remedy this problem, press the XLR GND switch in, to its “Lift” position,
to disconnect the ground wire (pin 1) from the XLR output. This action interrupts the
ground path and therefore breaks the loop.
Loop Inserts
Two signal loops are provided for the following applications: to connect external
equipment to the Pro Channel, to use only specific individual circuits, or to take direct
signal paths from specific sections. The connections are unbalanced ¼” (Tip = Hot (+),
Sleeve = Ground). Both of the Send jacks may be used without interrupting signal-flow
through the Pro Channel. The Return jacks break the signal-flow when a jack is
inserted.