Connecting Mains Power; Earthing - ALLEN & HEATH XONE 62 User Manual

Connecting Mains Power

USER
AC MAINS IN ~
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Earthing

The connection to earth (ground) in an audio system is important for two reasons:
1. SAFETY - To protect the operator from high voltage electric shock, and
2. AUDIO PERFORMANCE - To minimise the effect of earth (ground)
loops which result in audible hum and buzz, and to shield the audio
signals from interference.
For safety it is important that all equipment earths are connected to mains earth so that exposed
metal parts are prevented from carrying high voltage which can injure or even kill the operator. It is
recommended that the system engineer check the continuity of the safety earth from all points in
the system including microphone bodies, turntable chassis, equipment cases, and so on.
The same earth is also used to shield audio cables from external interference such as the hum
fields associated with power transformers, lighting dimmer buzz, and computer radiation. Problems
arise when the signal sees more than one path to mains earth. An 'earth loop' (ground loop) results
causing current to flow between the different earth paths. This condition is usually detected as a
mains frequency audible hum or buzz.
To ensure safe and trouble-free operation we recommend the following:
•
Have your mains system checked by a qualified electrician. If the supply earthing is solid to
start with you are less likely to experience problems.
•
Do not remove the earth connection from the console mains plug. The console chassis is
connected to mains earth through the power cable to ensure your safety.
connected to the console chassis internally. If problems are encountered with earth loops
operate the audio 'ground lift' switches on connected equipment accordingly, or disconnect the
cable screens at one end, usually at the destination.
•
Make sure that turntables are correctly earthed. A chassis earth terminal is provided on the
console rear panel to connect to turntable earth straps.
•
Use low impedance sources such as microphones and line level equipment rated at 200
ohms or less to reduce susceptibility to interference. The console outputs are designed to
operate at very low impedance to minimise interference problems.
•
Use balanced connections for microphones and mix output as these provide further
immunity by cancelling out interference that may be picked up on long cable runs. To connect
an unbalanced source to a balanced console input, link the cold input (XLR pin 3 or jack ring) to
0V earth (XLR pin 1 or jack sleeve) at the console. To connect a balanced XLR output to
unbalanced equipment, link the cold output to 0V earth at the console.
•
Use good quality cables and connectors and check for correct wiring and reliable solder
joints. Allow sufficient cable loop to prevent damage through stretching.
•
If you are not sure ... Contact your service agent or local Allen & Heath dealer for advice.
16
MONO OUT
Read the SAFETY INSTRUCTIONS printed at the
front of this User Guide and on the rear panel. Check
BOOTH AUX OUT
that the correct mains lead with moulded plug has
L L
been supplied with your console. The power supply
accepts mains voltages within the range 100-240V
R R
without changing any fuses or settings.
CLEAN FEED
SERIAL No:
It is standard practice to turn connected power
FUSE
amplifiers down or off before switching the console on
or off. This prevents any audible switch-on thumps.
Ensure that the IEC mains plug is pressed fully into the
rear panel socket before switching on.
Audio 0V is
XONE:62 User Guide