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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).
Phantom Power
Off
On
1
2
3
Page 2
Vox Muting
On
4
5
6
Bass Cut
Off
On
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.
Tone Routing
Tone
Off
Bypass
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.
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