Audio Connections; Balanced Wiring; Unbalanced Wiring; Ground Loop Control - BSS Audio DPR 404 User Manual

Audio connections

7.0 Audio connections
7.1 Balanced
wiring
7.2 Unbalanced
wiring
7.3 Ground loop
control
1 2
The DPR-404 audio inputs are RFI filtered and electronically balanced, with
the outputs electronically balanced and floating. They are designed to operate
at any signal level up to +20dBu and will drive into loads of 600 ohms or
greater. They will be 'fuss free', regardless of your installation's complexity.
Note that pin 1 of the input XLR is not connected to ground.
Whether your system is wired to a 'pin 3 hot' or a 'pin 2 hot' convention will
not matter as long as your wiring to both the input and output 3 pin XLR
connectors are the same . As is common with all other BSS equipment of this
type, we follow the convention of 'screen goes forward with the signal'. Input
cable screening therefore needs to be derived from the signal source end as
pin 1 is ground lifted for the inputs. You should use high quality audio cable
with 2 cores + screen for low noise and reliability, and to sidestep potential
problems.
If the equipment driving the DPR-404 has unbalanced outputs then you will
need to add a wire jumper such that the screen connection on Pin 1 of the
XLR is shorted to either Pin 2 or Pin 3, depending on the wiring convention of
the unbalanced equipment. If the equipment being connected to the DPR-404
outputs have only unbalanced inputs, then we recommend that you still use a
balanced (i.e. 2 core shielded) cable. The interconnecting cable should have
it's screen grounded by pin 1 of the DPR-404 output, the pin 3 output should
be connected the unbalanced input 0v ground, and the pin 2 output should be
connected to the live input. There should be no connection between the cable
screen and the 0v/chassis ground connection of the unbalanced equipment.
Strict adherence to this will help to eliminate potential ground loop hums by
removing signal currents from the cable screen.
Adherence to the wiring conventions noted above within a fully balanced
signal system will yield the best possible results with none of the problems
normally associated with interconnected audio equipment. Wherever possible,
cable screens should not be connected to any signal pin, but rather left to
perform a cable shielding function only. Where it is not possible to control all
of the external cabling, it might become necessary to have the internal
electronic ground of your unit separated from the case safety ground. Provision
is made internally within the DPR-404 to separate these two grounds at a
convenient point, or to add a suitable impedance network as part of a house
system requirement. Under no circumstances should the safety ground wire be
removed from the mains AC power connector as an interim measure to
achieve similar results. Please refer to section 13.2, for information on this
procedure.