Allen&Heath WZ 20S USER GUIDE
ALLEN&HEATH
MixWizard Series
WZ20S
Stereo Audio Mixing Console
USER GUIDE
Publication AP3634
Limited One Year Warranty
This product has been manufactured in the UK by ALLEN & HEATH and
is warranted to be free from defects in materials or workmanship for
period of one year from the date of purchase by the original owner.
To ensure a high level of performance and reliability for which this
equipment has been designed and manufactured, read this User Guide
before operating.
In the event of a failure, notify and return the defective unit to ALLEN &
HEATH or its authorised agent as soon as possible for repair under
warranty subject to the following conditions
Conditions Of Warranty
1. The equipment has been installed and operated in accordance with
the instructions in this User Guide
2. The equipment has not been subject to misuse either intended or
accidental, neglect, or alteration other than as described in the User
Guide or Service Manual, or approved by ALLEN & HEATH.
3. Any necessary adjustment, alteration or repair has been carried out
by ALLEN & HEATH or its authorised agent.
4. The defective unit is to be returned carriage prepaid to ALLEN &
HEATH or its authorised agent with proof of purchase.
5. Units returned should be packed to avoid transit damage
These terms of warranty apply to UK sales. In other territories the terms
may vary according to legal requirements. Check with your ALLEN &
HEATH agent for any additional warranty which may apply.
WZ20S User Guide AP3634 Issue 2.
Copyright © 2001 Allen & Heath Limited. All rights reserved
Manufactured in the United Kingdom by
Allen & Heath Limited
Kernick Industrial Estate, Penryn, Cornwall, TR10 9LU, UK
http://www.allen-heath.com
ALLEN&HEATH
2 WZ20S User Guide
Important Safety Instructions
WARNINGS - Read the following before proceeding :
CAUTION
ATTENTION: RISQUE DE CHOC ELECTRIQUE – NE PAS OUVRIR
Read instructions: Retain these safety and operating instructions for future reference.
Adhere to all warnings printed here and on the console. Follow the
operating instructions printed in this User Guide.
Do not remove covers: Operate the console with its covers correctly fitted. Disconnect mains
power by unplugging the power cord if the covers need to be removed
for setting internal options. Refer this work to competent technical
personnel only.
Power sources: Connect the console to a mains power only of the type described in
this User Guide and marked on the rear panel. Use the power cord
with sealed mains plug appropriate for your local mains supply as
provided with the console. If the provided plug does not fit into your
outlet consult your service agent for assistance.
Grounding: Do not defeat the grounding and polarisation means of the power cord
plug. Do not remove or tamper with the ground connection in the
power cord. This equipment must be grounded (earthed).
Power cord routing: Route the power cord so that it is not likely to be walked on, stretched
or pinched by items placed upon or against it.
Water and moisture: To reduce the risk of fire or electric shock do not expose the console
to rain or moisture or use it in damp or wet conditions. Do not place
containers of liquids on it which might spill into any openings.
Ventilation: Do not obstruct the ventilation slots or position the console where the
air flow required for ventilation is impeded. If the console is to be
operated in a rack unit or flightcase ensure that it is constructed to
allow adequate ventilation.
Heat and vibration: Do not locate the console in a place subject to excessive heat or
direct sunlight as this could be a fire hazard. Locate the console away
from any equipment which produces heat or causes excessive
vibration.
Servicing: Switch off the equipment and unplug the power cord immediately if it
is exposed to moisture, spilled liquid, objects fallen into the openings,
the power cord or plug become damaged, during lightening storms, or
if smoke, odour or noise is noticed. Refer servicing to qualified
technical personnel only.
Installation: Install the console in accordance with the instructions printed in this
User Guide. Do not connect the output of power amplifiers directly to
the console. Use audio connectors and plugs only for their intended
purpose.
WZ20S User Guide 3
Important Mains plug wiring instructions.
The console is supplied with a moulded mains plug fitted to the ac
mains power lead. Follow the instructions below if the mains plug has
to be replaced.
The wires in the mains lead are coloured in accordance with the
following code:
TERMINAL
European USA/Canada
LIVE BROWN BLACK
L
NEUTRAL BLUE WHITE
N
EARTH GND GREEN & YELLOW GREEN
E
If the colours of the wires in the mains lead do not correspond with the
coloured markings identifying the terminals in your plug, proceed as
follows:
The wire which is coloured Green and Yellow must be connected to
the terminal in the plug which is marked with the letter E or with the
Earth symbol.
The wire which is coloured Blue must be connected to the terminal in
the plug which is marked with the letter N.
The wire which is coloured Brown must be connected to the terminal
in the plug which is marked with the letter L.
Ensure that these colour codes are followed carefully in the event of
the plug being changed.
WIRE COLOUR
WARNING: This appliance must be earthed.
Mains electricity is dangerous and can kill. Mains voltage is
present within the console. Do not remove the covers with mains
electricity connected. Mains earth is connected to the console
chassis through the power lead to ensure your safety. Do not
remove this mains earth connection.
This product complies with the European Electromagnetic
Compatibility directives 89/336/EEC & 92/31/EEC and the
European Low Voltage Directives 73/23/EEC & 93/68/EEC.
Any changes or modifications to the console not approved by Allen &
Heath could void the compliance of the console and therefore the
users authority to operate it.
4 WZ20S User Guide
Introduction
ALLEN & HEATH continues its commitment to provide high quality audio mixing
equipment engineered to meet the exacting requirements of today’s audio business. The
WZ20S compact stereo mixing console brings you the latest in high performance
technology and offers the reassurance of over two decades of console manufacture and
customer support.
This user guide presents a quick reference to the function and application of the WZ20S.
We recommend that you read this fully before starting. Included is information on
installing, connecting and operating the console, panel drawings and technical
specification. A system block diagram is printed on the rear cover. For further information
on the basic principles of audio system engineering, please refer to one of the specialist
publications available from bookshops and audio equipment dealers.
Whilst we believe the information in this guide to be reliable we do not assume
responsibility for inaccuracies. We also reserve the right to make changes in the interest
of further product development.
Service And Technical Support
We are able to offer further product support through our world-wide network of approved
dealers and service agents. You can also access our Web site on the Internet for
information on our product range, assistance with your technical queries or simply to chat
about matters audio. To help us provide the most efficient service please keep a record
of your console serial number, and date and place of purchase to be quoted in any
communication regarding this product. The serial number is located on the connector
panel. A space is provided here for you to note this.
Console SERIAL NUMBER Date of purchase Place of purchase
Looking After Your Console
Your WZ20S is ruggedly constructed and should provide many years of reliable service
whether installed, location mixing or live gigging. However, you will extend the life of the
console and preserve its appearance by applying these simple common sense
precautions:
Damage : To prevent damage to the controls and cosmetics avoid placing heavy objects
on the control surface, scratching the surface with sharp objects, or rough handling and
vibration.
Environment : Protect from excessive dirt, dust, heat and vibration when operating and
storing. Avoid tobacco ash, smoke, drinks spillage, and exposure to rain and moisture. If
the console becomes wet, switch off and remove mains power immediately. Allow to dry
out thoroughly before using again.
Cleaning : Avoid the use of chemicals, abrasives or solvents. The control panel is best
cleaned with a soft brush and dry lint-free cloth. The faders, switches and potentiometers
are lubricated for life. The use of electrical lubricants on these parts is not recommended.
Transporting : The console may be transported as a free-standing unit or mounted in a
rack or flightcase. Ensure that the connector pod is secured in place with the locking
screws fitted to prevent movement. Protect the controls from damage during transit. The
faders are best positioned at the top of their travel if the console is transported without a
suitable flightcase, rack or carton. Use adequate packing if you need to ship the unit.
WZ20S User Guide 5
Overview of the MIXWIZARD WZ20S
The WZ20S is a compact audio mixing console with many stereo inputs. It is well suited
to mixing stereo sources such as keyboards, voice modules and effects returns, or for
recording or stage submixing. With its additional mic inputs it is also equipped for low
end broadcast, club installation and production mixing. The WZ20S complements the
MixWizard range which also includes the multi mic input WZ12DX and WZ16DX with built
in effects processors, and the WZ14:4:2+ which is dual function 4 buss live mixer.
The WZ20S has 12 input channel strips. Four mono channels accept any signal, mic or
line, on either jack or XLR. Eight stereo strips feature dual A and B inputs so that one of
two stereo sources can be selected, or they can be mixed together with individual control
of gain. This allows permanent connection of 16 stereo sources. Inputs A are on phono
pin jacks and inputs B on TRS jacks. An optional RIAA card can be fitted to the phono
inputs. The jack inputs are balanced and normalled for use with stereo or mono sources.
An additional two stereo external inputs are available and can be configured as returns to
the mix or as external inputs for monitoring only.
The mono channels provide 4 band EQ with shelving high and low, and two parametric
mid bands. The stereo channels provide 4 band EQ with shelving high and low, and two
fixed frequency mid bands. All equalisers include in/out switching.
The WZ20S provides two independently assignable stereo mix busses MIX1 and MIX2.
Each feeds a pair of balanced XLR outputs together with inserts and metering. In
addition, MIX2 includes a second stereo output on TRS jacks and a summing mono
output on balanced XLR. Mix1 can be assigned to feed MIX2 to provide a stereo
subgroup if required. 6 independent aux outputs on TRS jacks include pre/post switching
in groups of two and four. This flexible output scheme satisfies many applications
including dual stereo submixing, stereo and mono broadcast and amplifier feeds,
cleanfeed sends, zone and recording feeds.
A unique combination of monitoring features is provided to satisfy the specific
requirements of live mixing, broadcast and club install. Dedicated headphones and local
monitor outputs include separate level control. A large switch bank lets you select any
output for monitoring, automatically overriden by channel PFL selection. Two
headphones can be connected, one on the top panel, one on the rear, for example in a
presenter/guest situation. The local monitor feeds separate TRS jacks and includes mute
(internally configurable for 20dB dim) and PFL enable facilities. Split PFL can be
selected to keep the output program in the right ear while monitoring the PFL channel in
the left, ideal for broadcast or club booth monitoring. A switch allows instant checking of
the stereo signal for mono compatibility.
In keeping with the rest of the range, the WZ20S offers the QCC (Quick Change
Connector) rotating pod which can be set for 8U high 19” rack or rear connector desktop
operation. 100mm faders and professional build quality using individual channels with
nutted pots and all steel chassis provide solid reliability and easy servicing. The internal
power unit is an efficient switched mode design which allows universal connection to the
most common world wide mains voltages.
The layout is simple and intuitive and includes tamperproof underpanel switches for
configurable functions, important for broadcast and club applications.
There are several internal configuration options to further customise the console for more
specialist applications. These include aux pre/post and mono/stereo links, SYS-LINK
expander output card, RIAA preamp cards, optional switched faders for remote start/stop,
local monitor auto dim from fader or switch, and custom wiring to 25pin D connector.
These options should be configured by competent service or installation personnel. For
further details please contact your ALLEN & HEATH agent.
Finally, in keeping with the ALLEN & HEATH design philosophy, the WZ20S carries
forward the sonic purity of analog MSP (Minimum Signal Path) engineering to ensure the
very best audio performance.
6 WZ20S User Guide
Front Panel Layout
For clarity only the first two stereo channels are shown.
MixWizard
PAD
-30dB
40
30
GAI N
50
PAD
20
- 10
60 30
100Hz
0
HF
12kHz
-15
+15
3kHz
1k
5k
7k
700
15kHz
500Hz
0
MF1
-15
+15
180Hz
60
300
45
450
35Hz
1kHz
0
MF2
-15
+15
0
LF
60Hz
-15
+15
EQ
IN
AUX
1
0
OO
+6
AUX
2
0
OO
+6
AUX
3
0
OO
+6
AUX
4
0
OO
+6
POST
PRE
AUX
5
0
OO
+6
AUX
6
0
OO
+6
POST
PRE
PAN
L
R
ON
PEAK
!
PFL
10
MIX1
5
MIX2
0
-30dB
30
GAI N
PAD
20- 10
0
HF
12kHz
-15
3kHz
1k
700
500Hz
0
MF1
-15
180Hz
60
45
35Hz
0
MF2
-15
0
LF
60Hz
-15
EQ
IN
AUX
1
OO
AUX
2
OO
AUX
3
OO
AUX
4
OO
AUX
5
OO
AUX
6
OO
PAN
L
PEAK
!
PFL PFL PFL PFL PFL
10
MIX1
MIX2
5
0
10
GAI N
-5
PAD
40
50
60 30
100Hz
+15
5k
7k
15kHz
+15
300
450
1kHz
+15
+15
0
+6
0
+6
0
+6
0
+6
POST
PRE
0
+6
0
+6
POST
PRE
R
ON
5
0
PAD
-30dB
40
30
GAI N
50
PAD
20- 10
60 30
100Hz
0
HF
12kHz
-15
+15
3kHz
5k
1k
7k
700
15kHz
500Hz
0
MF1
-15
+15
180Hz
60
300
45
450
35Hz
1kHz
0
MF2
-15
+15
0
LF
60Hz
-15
+15
EQ
IN
AUX
1
0
OO
+6
AUX
2
0
OO
+6
AUX
3
0
OO
+6
AUX
4
0
OO
+6
POST
PRE
AUX
5
0
+6
OO
AUX
6
0
OO
+6
POST
PRE
PAN
L
R
ON
PEAK
!
10
MIX1
5
MIX2
0
PAD
-30dB
40
30
GAI N
50
PAD
20- 10
60 30
100Hz
0
HF
12kHz
-15
+15
3kHz
5k
1k
7k
700
15kHz
500Hz
0
MF1
-15
+15
180Hz
60
300
45
450
35Hz
1kHz
0
MF2
-15
+15
0
LF
60Hz
-15
+15
EQ
IN
AUX
1
0
OO
+6
AUX
2
0
OO
+6
AUX
3
0
OO
+6
AUX
4
0
OO
+6
POST
PRE
AUX
5
0
+6
OO
AUX
6
0
OO
+6
POST
PRE
PAN
L
R
ON
PEAK
!
10
MIX1
5
MIX2
0
15
20
-10
ON
5
0
10
GAI N
-5
15
-10
20
ON
MONO
0
HF
12kHz
-15
+15
0
MF1
-15
+15
0
MF2
-15
+15
0
LF
60Hz
-15
+15
EQ
IN
AUX
1
0
OO
+6
AUX
2
0
OO
+6
AUX
3
0
O4O
+6
AUX
0
OO
+6
POST
PRE
AUX
5
0
OO
+6
AUX
6
0
OO
+6
POST
PRE
BAL
L
R
ON
PEAK
!
10
MIX1
5
MIX2
0
5
5
0
10
GAI N
-5
15
20
-10
ON
5
0
10
GAI N
-5
15
-10
20
ON
MONO
0
HF
12kHz
-15
+15
0
MF1
-15
+15
0
MF2
-15
+15
0
LF
60Hz
-15
+15
EQ
IN
AUX
1
0
OO
+6
AUX
2
0
OO
+6
AUX
3
0
O4O
+6
AUX
0
OO
+6
POST
PRE
AUX
5
0
OO
+6
AUX
6
0
OO
+6
POST
PRE
BAL
L
R
ON
PEAK
!
10
MIX1
5
POWER ON
MIX1
MIX2
EXT1
IN
O
O
+16
+9
+6
+3
0
-6
-9 -9
-16
-20
-30
MIX1
AUX
1
O
O
AUX
2
O
O
AUX
3
O
O
AUX
4
O
O
AUX
5
O
O
AUX
6
OO
MIX2
10
5
RL
+6
+4
+4
+4
+4
+4
+4
SPLIT
PFL
MONO
EXT2
IN
0
0
1-2
0
0
3-4
0
5-6
0
0
1
MIX2
0
+6
OO
PRG
PFL
SPLIT PFL
+16
+9
+6
+3
0
-3-3
-6
-12-12
-16
-20
-30
L
R
MONITOR
PFL
5
4
6
LEV
3
7
2
8
1
9
010
1
AUX1
AUX2
2
AUX3
3
AUX4
4
AUX5
5
AUX6
6
EXT1
EXT2
ALL UP =
MIX2
MIX1
PFL ENABLE
5
4
6
LOCAL
3
7
MONITOR
2
8
1
9
1
0
0
DIM
MIX2MIX1
10
5
MIX2
0
5
00
5
5
10
10
10
10
10
10
10 10
WZ20S
20
30
OO
20
30
OO
20
30
OO
20
30
OO
DUAL
STEREO
20
30
OO
WZ20S User Guide 7
DUAL
STEREO
20
30
OO
20
30 30
OO OO
20
Rear Panel Layout
MIX 2
L
OUT
R
MIX2
OUT
R
L
INSERT
R
MIX1
LL
OUT
R
M
2
TIP = L
RING = R
A DIVI SION OF HARMAN I NTERNATIONAL I NDUSTRIES Lt d.
L
LOCAL MONITOR
R
Made in the UK by ALLEN & HEATH
MIX 1
L
19-20 17- 18 15-16
INSERT
A
IN
L
R
R
B
IN
M
L /
R
6
5 4
AUX
AUX
EXT I N 2
SYS-LI NK OUT
(option)
AUX
L
R
INA
IN
INA
L
R
B
L /
R
L
R
B
IN
M
M
L /
R
2
3
AUX
AUX AUX
EXT IN 1
L
R
REMOTE
(user connec tions)
STEREO INPUTS
13-14 11- 12
INA
L
R
B
IN
M
L /
R
SENDS
1
XLR OUT
2
1
+OUT
3
- OUT
TIPTIP +
LINE
IN/OUT
IMPEDANCE BALANCED
INSERT
SEND
TIPTIP
RINGRING
RETURN
MixWizard
SERIAL No:
MONO INPUTS
9-10 7-8 5-6
INA
IN
RINGRING -
INA
L
R
B
IN
M
L /
R
+IN
1
2
- IN
3
INPUT
INA
L
R
B
IN
M
L /
R
TIPTIP + IN
RING -INRING
20SWZ
INA
L
R
B
L /
R
TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK
DO NOT EXPOSE THIS APPARATUS TO RAIN OR MOISTURE.
WARNING: FOR CONTINUED PROTECTION AGAINST RI SK OF FIRE
ATTENTION: REMPL ACER LE FUSIBLE AVEC UN DES MEMES CARACTERISTI QUES.
L
R
B
IN
M
M
L /
R
CAUTION
AVIS: RISQUE DE CHOC ELECTRIQUE - NE PAS OUVRIR.
100 - 240V~ T500mA 250V 20mm
REPLACE FUSE WITH SAME TYPE AND RATING
INSERT
IN
DIR
OUT
4
FUSE
3
INSERT
IN
DIR
OUT
34
MIC 4
+ 48V
MIC 3
+48V
WARNING - THIS APPARATUS MUST BE EARTHED.
AC MAINS IN ~
XLR connections are Pin 2 = hot (+) Pin 3 = cold (-) Pin 1 = GND
TRS input and output connections are Tip = hot (+) Ring = cold (-) Sleeve = GND
TRS insert connections are Tip = SEND Ring = RETURN Sleeve = GND
INSERT
IN
2
INSERT
IN
1
2 134
2
DIR
OUT
1
PHANTOM POWER
MIC 2
+ 48V
SUPPLY VOLTAGE RANGE:
100 - 240V
47-63Hz ~ 30W MAX
MIC 1
+ 48V
~
DIR
OUT
REFER TO USER GUIDE BEFORE CONNECTING SUPPLY
NO USER SERVICEABLE PARTS INSIDE.
REFER SERVI CI NG TO QUAL IF IED S ERVICE P ERSONNEL.
ONOFF
Input Connections
MONO IN (XLR) Balanced XLR female 2k ohm -60 to –20dBu PAD out
>10k ohm -30 to +10dBu PAD in
MONO IN (TRS) Balanced TRS jack >10k ohm -30 to +10dBu
STEREO IN A RCA phono >10k ohm -20 to +10dBu
STEREO IN B Balanced TRS jack >10k ohm -20 to +10dBu
EXT IN 1,2 Balanced TRS jack >10k ohm -10dBV (+4dBu option)
Inserts
MONO Channel Unbalanced TRS jack SEND <75 ohm 0dBu
RETURN >3k ohm
MIX OUT 1,2 Unbalanced TRS jack SEND <75 ohm -2dBu
RETURN >7k ohm
Output Connections
DIR OUT 1-4 Impedance balanced TRS jack <75 ohm 0dBu
MIX OUT 1,2 (XLR) Balanced XLR male <75 ohm +4dBu
MIX OUT 2 (TRS) Impedance balanced TRS jack <75 ohm -2dBu
MONO OUT Balanced XLR male <75 ohm +4dBu
AUX OUT 1-6 Impedance balanced TRS jack <75 ohm -2dBu
HEADPHONES 1,2 Tip = L Ring = R 30 to 600 ohm recommended
8 WZ20S User Guide
Specifications
0dBu = 0.775 Volts rms +4dBu = 1.23V rms
0dBV = 1 Volt rms -10dBV = 316mV rms
Console Specifications
Maximum output level XLR +26dBu into >2k ohm load
TRS jack +21dBu into >2k ohm load
Internal headroom Channels +21dB
Mix to output +23dB
Peak indicators Turn on 5dB before clipping
Meters MIX 1,2 / MONITOR Peak reading 12 led 3 colour
Frequency response +0/-1dB 20Hz to 50kHz
Distortion < 0.006% THD+noise measured at +14dBu 1kHz
Crosstalk < 90dB Channel shutoff measured at 1kHz
Noise Measured rms 22Hz to 22kHz
MIC EIN -128dB referred to 150 ohm source
Residual output noise XLR -90dBu (-94dB S/N)
TRS jack -94dBu (-94dB S/N)
Mix noise, ch routed XLR -86dBu (-90dB S/N)
TRS jack -90dBu (-90dB S/N)
Power Supply
Internal switch mode power unit with auto sensing mains input.
MAINS IN socket IEC 3 pin
Power lead Country dependent with moulded mains plug supplied
AC mains 100 to 240V AC @ 50/60Hz
Consumption 35W max
Mains fuse rating 100-240V AC T500mA 20mm
Dimensions and Weights
The connector pod can be rotated and fixed in one of two positions to allow either
desktop operation with rear facing connectors, or 19” rack mounting with underside
connectors in 10U space.
Width Height Depth
Desktop 483mm (19”) 192mm (7.6”) 530mm (20.9”)
Rack mounted 483mm (19”) 444mm (17.5”) 10U 135mm (5.3”)
Packed 590mm (23.2”) 260mm (10.2”) 610mm (24”)
Unpacked Packed
Weight 10kg (22lbs) 13kg (29lbs)
WZ20S User Guide 9
Installing the Console
The MixWizard Series features the ALLEN & HEATH Quick Change Connector (QCC)
system. The rear connector pod may be hinged and locked into either of two positions.
Rear connectors allow desktop operation with the control panel sloped at a convenient 15
degrees. Underside connectors allow 19" rack mounting in a compact 10U space. The
connector position can be easily changed at any time to fit your application.
To change the
position remove the
crosshead locking
screw on each side,
swing the connector
pod into position, and
refit the two screws
19” Rack Mounting
Desktop Operation
PRECAUTION :
Do not transport or carry the
console with the locking screws
removed.
Do not attempt to remove the
connector pod from the console.
Mount the console in the
rack using 4x M6 bolts
each side for maximum
strength. We recommend
you fit the bolts with plastic
cup washers to protect the
panel, and they look
good... These should be
available from the supplier
of the rack unit or good
hardware store.
Flightcasing
The console can be easily
flightcased in either
connector mode. Provide
the dimensions shown here
to your flightcase supplier.
The console is fitted with
rubber feet to ensure it does
not slip or scratch the work
surface. The control panel
is angled at 15 degrees for
operating convenience.
10 WZ20S User Guide
Connecting Mains Power
TO REDUCE T HE RIS K OF FI RE OR ELECTRI C SHOCK
DO NOT EXPOSE THIS APPARATUS TO RAIN OR MOISTURE.
CAUTION
AVIS: RISQUE DE CHOC ELECTRIQUE - NE PAS OUVRIR.
100 - 240V~ T500mA 250V 20mm
WARNING: FOR CONTINUED PROTECTION AGAINST RISK OF FIRE
REPLACE FUSE WITH SAM E TYPE AND RATING
ATTENTION: REMPLACER LE FUSIBL E AVEC UN DES MEMES CARACTERISTIQUES.
Earthing
The connection to earth (ground) in an audio system is important for two reasons:
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:
WARNING - THIS APPARATUS MUST BE EARTHED.
SUPPLY VOLTAGE RANGE:
100 - 240V
47-63Hz ~ 30W MAX
OFF
FUSE
AC MAINS IN ~
REFER TO U SER GUI DE B EFORE CONN ECTI NG SUP PLY
NO USER SERVI CEABLE PARTS INSIDE.
REFER SERVICING TO QUALIFIED SERVICE PERSONNEL.
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.
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.
ON
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.
• 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.
WZ20S User Guide 11
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