ALLEN & HEATH XONE 62, Service Manual

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16 XONE:62 Service Manual
Plugging Up The System
The XONE:62 uses professional grade 3 pin XLR, 1/4" TRS jack and RCA PHONO
sockets. To ensure best performance, we recommend the use of high quality audio
cables and connectors, and that time is taken to check for reliable and accurate cable
assembly. It is well known that most audio system failures are due to faulty
interconnecting leads. The following mating plugs may be used to connect audio signals
to the console:
All input and output XLR connectors are 3 wire differentially balanced. These have 3
connector pins: Pin 1 = ground (screen), Pin 2 = signal hot (+), Pin 3 = signal cold (-).
All the jack sockets are the 3 pole TRS type. These are wired to work with both the
balanced TRS or the unbalanced 2 pole TS type plugs. The sockets have 3 connector
pins: Inputs and outputs are Tip = signal hot (+), Ring = signal cold (-), Sleeve = ground
(screen). Insert connections are Tip = send, Ring = return, Sleeve = ground.
The RCA phono connectors are the 2 wire unbalanced type typical of those found on
equipment such as CD players, turntables and domestic amplifiers.
Avoid rev and - on balanced connections as this will result in out of phase signals
(reverse polarity) which may cause signal cancellation effects.
For live work where long cables runs are required, balanced interconnections should be
used. However, interconnections between more affordable 2-wire (signal, ground)
unbalanced equipment and the console are unlikely to cause problems if the cables are
kept short. Refer to the following diagram for unbalanced to balanced connections.
Dealing with Ground Loops, Buzz and Interference
For optimum performance all audio signals should be referenced to a solid, noise-free
ground (earth) point, frequently referred to as the ‘star point’ or ‘clean earth’.
A ground loop is created when the signal has more than one path to ground. Should you
experience hum or buzz caused by ground loops, check first that each piece of
equipment has its own separate path to ground. If so, operate ground lift switches on
connected equipment in accordance with the instruction manuals. Alternatively
disconnect the cable screen at the destination end only. This breaks the offending loop
while still maintaining the screening down the length of the cable.
WARNING For your safety do not remove the earth (ground) connection in the
power lead of the console or connected equipment.
To avoid interference pickup keep audio cables away from mains power units and cables,
thyristor dimmer units or computer equipment. Where this cannot be avoided, cross the
cables at right angles to minimise interference.