Allen&Heath WZ 20S USER GUIDE - Manual (Page 11)

WZ20S User Guide 11
NO USER SERVICEABLE PARTS INSIDE.
SUPPLY VOLTAGE RANGE:
100 - 240V
REFER SERVICING TO QUALIFIED SERVICE PERSONNEL.
47-63Hz ~ 30W MAX
WARNING - THIS APPARATUS MUST BE EARTHED.
REFER TO USER GUIDE BEFORE CONNECTING SUPPLY
TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK
DO NOT EXPOSE THIS APPARATUS TO RAIN OR MOISTURE.
AVIS: RISQUE DE CHOC ELECTRIQUE - NE PAS OUVRIR.
REPLACE FUSE WITH SAME TYPE AND RATING
WARNING: FOR CONTINUED PROTECTION AGAINST RISK OF FIRE
ATTENTION: REMPLACER LE FUSIBLE AVEC UN DES MEMES CARACTERISTIQUES.
100 - 240V~ T500mA 250V 20mm
CAUTION
FUSE
OFF
AC MAINS IN ~
ON
~
Connecting Mains Power
Read the SAFETY INSTRUCTIONS printed at
the front of this User Guide. Check that the
correct mains lead with moulded plug has been
supplied with your console. The power supply
accommodates mains voltages within the range
100-240V without changing any fuses or settings.
It is standard practice to turn connected power
amplifiers down or off before switching the
console on or off. Ensure that the IEC mains
plug is pressed fully into the rear panel socket
before switching on.
Earthing
The connection to earth (ground) in an audio system is important for two reasons:
1. SAFETY - To protect the operator from high voltage 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 sound engineer check the continuity of the
safety earth from all points in the system including microphone bodies, guitar strings,
connector cases, equipment panels 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.
Audio 0V is 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.
• 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 where possible 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
console output to an unbalanced destination, 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 or local Allen & Heath agent for advice.