Redback A 4420B User manual

A 4420B
Public Address Mixer
®
www.altronics.com.au
Proudly Assembled in Australia
Operating
Instructions
Distributed by Altronic Distributors Pty. Ltd. Perth. Western Australia.
Phone: [phone] Fax: [phone]
Internet: www.altronics.com.au

REDBACK A 4420A Mixer
Congratulations on purchasing the A 4420A REDBACK 8 Input Mixer.
This mixer has been designed to meet the requirements of today’s
high performance PA Systems.
The input section features I.C. balancing techniques to reduce hum
and noise to very low levels while maintaining excellent balancing and
input sensitivity. Naturally, if you want to use unbalanced micro-
phones then it is simply a matter of connecting one of the input signal
lines to earth (see figure 2).
The Mixer Features
• Phantom Powering available (individually selectable on each chan-
nel) on all microphone inputs if desired (internally selected). This
function is factory set “OFF”
• VOX (Voice activated) muting of the auxiliary music inputs (inter-
nally selectable on or off) when any of the microphone inputs are
used. This function is factory set “OFF”.
• The microphones have a Bass cut switch to reduce feedback and
improve vocal clarity (internally selectable on or off). This function
is factory set “OFF”.
• Bass and Treble Controls for the Auxiliary inputs.
• The microphone inputs can be selected to either channel through,
or bypass the tone controls (internally selectable on or off). This is
factory set in the “BYPASS” position.
• Internationally accepted IEC socket for mains power connection.
Note this unit is designed for 240V AC 50Hz operation only.
• Supplied with Industry standard 3 pin XLR connectors for micro-
phone inputs and stereo RCA’s for Auxiliary inputs.
• The output of the mixer has been designed to operate with power
amplifiers equipped with a balanced input . If you wish to drive an
unbalanced amplifier, then simply connect one of the output sig-
nal lines of the mixer to Earth, and use the other output (see fig-
ure 2).
Instructions For Use
Remove the mixer from its packaging and inspect for any damage. If
the unit appears to be damaged then do not operate as this may
damage the unit further.
1. Prior to installation, set the internal jumpers. These are located
as per figure 1. WARNING Do not open unit when connect-
ed to the mains voltage.
2. Plug in a low impedance microphone into the microphone input,
or a music source (tape or Compact Disc or similar) into the auxil-
iary input.
3. Connect the mixer to an amplifier using a suitable cable. See fig-
ure 2, Connection Details.
4. Turn all controls fully down and then switch the mixer and amplifi-
er on.
5. Turn up the level control associated with the input that you are
using to about half way. Talk into the microphone (or play some
music) and adjust the Master level to achieve the required level.
For the best noise performance turn the input level control to a high
setting and use the Master as the volume control. Use the other input
level controls to set the required mixing ratios. If you are using the
auxiliary inputs, adjust the bass and treble controls to get the desired
sound. If you have the tone routing jumper set to “TONE”, you may
also adjust the Bass and Treble controls when using microphone(s) to
get the desired sound.
For best performance when using long lines between
microphones/mixer and or amplifier use balanced lines. These have
the effect of cancelling out any noise or hum that may be induced into
the cables. Note that a balanced line uses three wires (two signal
wires and one earth wire or shield) where an unbalanced cable uses
only one signal wire and an earth. See the connection details (figure
2) for wiring up plugs etc.
Do not tamper with the unit. Warning Mains Voltage is Present Inside.
Leave servicing to qualified personnel.
Page 2
Phantom Power Vox Muting Tone Routing
Bass Cut
Bypass
On
Off
On
123456
Off
OnOff
Tone
Figure 1:
Top view of the PCB
showing jumper
positions, with
factory default
settings.
Note these should not
be adjusted when
connected to the
mains power.

REDBACK A 4420A Mixer
Auxiliary
No. of Channels:.................................................................2
Sensitivity (master full): ............................................260mV
Signal to Noise Ratio:.................................better than 76dB
Frequency Response (±3dB): .........................60Hz - 20kHz
Input Impedance:.................................................100k Ohm
Muting Level:...............................................................-50dB
Mode:..................................................................Unbalanced
Connector Type:..................................................Stereo RCA
Tone Controls
Bass Control: ..................................................±9dB at 80Hz
Treble Control:............................................±10dB at 10kHz
Bass Cut Switch on Microphone
Switch “ON”:..................................-6dB/Octave from 150Hz
Phantom Power
Voltage:...........................................................................12V
Output Impedance:................................................3.4k ohm
Microphone
No. of Channels:.................................................................6
Sensitivity (master full): .............................................1.2mV
Signal to Noise Ratio:.................................better than 71dB
Frequency Response (±3dB): .......................60Hz to 20kHz
Input Impedance: ..................................................600 Ohm
Mic Impedance:...............................200 - 600 Ohm nominal
Mode:......................................................................Balanced
Connector Type:........................................3 Pin XLR Female
Output
Signal to Noise Ratio :
(all controls mid way) ..............................-85dB, ref 0dBm
(all controls maximum)............................-58dB, ref 0dBm
Impedance: ..........................................................600 Ohms
Distortion:....................................................Less than 0.06%
Max Output Level:...................................................+19dBm
Mode:......................................................................Balanced
Connector Type:............................................3 Pin XLR Male
*Specifications subject to change without notice.
Page 3
1
2
3
Signal
Input
Unbalanced
1
2
3
Signal
XLR Mic
Input
From Microphone
Input
Balanced
12
3
Output
Unbalanced Signal
RCA
Shield For Stereo
Amplifiers
RCA
XLR Line
Output
12
3
XLR Line
Output
1
2
3
Shield
XLR Amp
Input
Output
Balanced
Shield
XLR Mic
Input Shield
From Microphone
Figure 2.
Connection Details
Microphone Connections
Connector Type:..................XLR 3Pin Female
Pin 1:.....................................................Earth
Pin 2:...............................Signal Inphase (hot)
Pin 3:......................Signal Out of Phase (cold)
Output Connections
Connector Type: .....................XLR 3Pin Male
Pin 1:.....................................................Earth
Pin 2:...............................Signal Inphase (hot)
Pin 3:......................Signal Out of Phase (cold)
Trouble Shooting
Fault/Symptom: No Sound
• Check that there is power on both the mixer and power amplifier.
The mixer has a LED light to indicate if there is power.
• Check master volume is turned up.
• Check the fuse. CAUTION: Unplug the mixer from mains power
before checking fuse.
• Check all lead connections
Fault/Symptom: When Paging the Music is Not Muted
• Set the VOX Muting internal jumper to “ON”.
Fault/Symptom: Bass Control Fails to Give Bass Boost
• Check that the Bass Cut internal jumper is selected “OFF”
Fault/Symptom: Microphone Does Not Work
• The microphone may need phantom power. If so set the Phantom
Power internal jumper(s) to “ON”.
• Check microphone volume is turned up.
Fault/Symptom: Tone Controls Do Not Work on Mic
• Set the Tone Routing internal jumper to “TONE” setting.

REDBACK A 4420A Mixer
Page 4
CHASSIS MOUNTED,
R47 2k2
C23 33pf
R18 47k
-12
+12
C18 1 C17 1
R37 10 R36 10
13 560p
C49 33p
R29 33k
R24 33k
R26 47k
R23 47k R28
47k
RV10 1M
RV9 100k
R15 47k
R50 10k
C15 1
-12
+12
C28 1 C34 1
R25 10 R42 10
C33 330nf
SW2
SW3
SW1 R44
10k
+12
-12
-12
+12
2 3
6
74
IC3 TL071
Q4 BC327 Q3 BC337
Q5 TIP31C
Q2 548
Q1 548
6 5
7
IC5B
TL072
2 3
1
84
IC5A TL072
6 5
7
IC6B TL072
2 3
1
84
IC6A TL072
R84 4k7 R83 4k7 R82 4k7 R81 4k7
SK11 SK10 SK9 SK8
R68 22k
RV6 1k
C5 10
C60 4n7
C61 4n7
R10 6k8 R9
6k8
C92 10 C93 10
C71 150p
C70 100p
R106 10k
R78 3k3
R105 10k
R104 10k
R61 330
R62 330
6 5
7
U7B LM833
2 3
1
84
U7A LM833
R79 10 R63 10
C48 10
C47 10
+12
-12
1
2 3
SK6 3PIN
SW5A5 +12
R67 22k
RV5 1k
C4 10
C58 4n7
C59 4n7
R7 6k8 R8
6k8
C90 10 C91 10
C69 150p
C68 100p
R103 10k
R59 3k3
R102 10k
R101 10k
R56 330
R57 330
6 5
7
U6B LM833
2 3
1
84
U6A LM833
R60 10 R58 10
C46 10
C45 10
+12
-12
1
2 3
SK5 3PIN
SW5A4 +12
R66 22k
RV4 1k
CC3 10
C56 4n7
C57 4n7
R6 6k8 R5
6k8
C88 10 C89 10
C67 150p
C66 100p
R100 10k
R54 3k3
R99 10k
R98 10k
R45 330
R48 330
6 5
7
U5B LM833
2 3
1
84
U5A LM833
R55 10 R53 10
C27 10
C16 10
+12
-12
1
2 3
SK4 3PIN
SW5A3 +12
RR52 22k
RV3 1k
CC2 10
C54 4n7
C55 4n7
R3 6k8 R4
6k8
C86 10 C87 10
C65 150p
C64 100p
R97 10k
R33 3k3
R96 10k
R95 10k
R21 330
R31 330
6 5
7
U4B LM833
2 3
1
84
U4A LM833
R34 10 R32 10
C9 10
C8 10
+12
-12
1
2 3
SK3 3PIN
SW5A2 +12
RR27 22k
RV2 1k
C1 10
C52 4n7
C53 4n7
R1 6k8 R2
6k8
C84 10 C85 10
C63 150pC62 100p
R94 10k
R13 3k3
R93 10k
R92 10k
R11 330
R12 330
6 5
7
U3B LM833
2 3
1
84
U3A LM833
R19 10 R43 10
C6 10
C7 10
+12
-12
1
2 3
SK2 3PIN
SW5A +12
+12
SW5A1
1
2 3
SK1 3PIN
-12
+12
C42 10
C43 10
R72 10 R73 10
2 3
1
84
U1A LM833
6 5
7
U1B LM833
R75 330
R74 330
R85 10k
R86 10k
R69 3k3
R87 10k
C50 100p C51 150p
C39 10 C38 10
R71 6k8
R70 6k8
C41 4n7 C40
4n7
C44 10
RV1 1k R14
22k
RV7 10k RV8 10k
C26 100n C25 100n
R16 22k R17 22k
2
3
6
7
4
8 1
5
U2 SSM2142
R40 10 R41 10
R76 150 R77 150
1
2 3
SK7 3PIN
CC21 10 C22 10
RV11 1k
R38 10 R39 10
C19 10 C20 10
R30 47k
C94 33pf
R64 10k
R46 10k
R49 1k R51
470k
C35 10
D5 914
D6 914
R65 100k R20 100k
C36 47
+12
1
A7
1
A8
R22 10k
+12
R80 100k
C12 100
TX1 M2855
F1 500ma
MAINS
1 2 3
P1 3PIN
FGND
1 2 3 4
P2
1 2 3 4
T1
C30
100nf
D1 4002
D2
4002
D3
4002
D4
4002
C29 2200 C10 2200
1
2
3
IC8 7812
1
2 3
IC7 7912
C11 100nf
C24
100nf
C31 10 C32 10
+12
-12
1 2
U10A 40106
3 4
U10B 40106
5 6
U10C 40106
1 2
U10:DA 40106
1011
U10E 40106
1213
U10F 40106
ZD1 18/1
R91 1k C98
10
C99 100
D9 4004
VDD
R88 10k
C95 1nf
R90 2k2 R89 2k2
C96 47/63 D7
5819
D8 5819
+12
LED1 red
R35 680
1 2
SK12
BASS CUT
NORM TONE
MIC TONE ROUTING
MUTE
VOX-MUTE
POWER ON
AUX 1 AUX 2 MIC 1 MIC 2 MIC 3 MIC 4 MIC 5 MIC 6
DC SOCKET 24V IN
C14 6n8
+
C37 1uF
C29
22pf
C82 22pf