A 4425
Public Address Mixer
Operating Instructions
®
www.altronics.com.au
M
IXER
O
VERVIEW
Description
This Redback
®
8 channel mixer has been designed to
meet the requirements of professional public address
installations. Its many features makes it ideally suited for
use in shopping centres, gymnasiums, places of worship,
office complexes, board rooms, council chambers, court
rooms etc.
Inputs and Outputs
Inputs 1-6 can be configured for balanced microphone or
line use as desired. XLR and dual RCA sockets are
provided for each of these inputs. Inputs 7 & 8 are
dedicated line inputs provided with dual RCA sockets and
variable muting/ducking level. Outputs are 600
Ω
/0dBm
XLR balanced or dual RCA sockets for record/tape out.
Input Configuration
Inputs 1-6 include an individual 4 way dip switch enabling
selection of mic or line input operation, adjustable line
input sensitivity (100mV or 1V), mic or line operation of
priority/VOX muting (see below for priority details) and
phantom power on/off.
A DIP switch is provided for inputs 7 & 8 enabling the
adjustment of the input sensitivity (100mV or 1V).
Front Panel Controls
The front panel includes individual volume controls and
tamper proof, screw driver adjust, treble and bass
controls for each input channel. A LED VU meter and a
headphone socket are provided.
Priority and Muting
The mixer incorporates three levels of priority. Inputs 1,2
and 3 will operate the priority/VOX muting regardless of
the input configuration
ie: both microphone and line
inputs will operate the priority/VOX circuit if this
function is selected ON for that input.
This is
particularly useful when an input is set for line use, as it
enables telephone paging, radio microphone, emergency
tones, jukebox or similar to mute background music on
other inputs.
Three level priority operates as shown:
Input 1
Priority 1 – mutes inputs 2 - 8,
Input 2
Priority 2 – mutes inputs 3 – 8,
Input 3
Priority 3 – mutes inputs 4 – 8,
Inputs 4-8 are mixed. If the priority function for inputs 1-3
is turned off, then inputs assume no priority and its output
will be mixed with inputs 4-8 ie. if all priority functions are
switched OFF then all inputs will be mixed.
When fitted the optional A 2073 assumes priority 2.
Adjusting VOX muting sensitivity
The adjustment pots are located internally. See page 2
for diagram.
1.
Switch off the unit and remove the 240V mains lead
and 24V in from the rear.
2.
Remove the 6 x M3 screws from the lid and remove
the lid.
3.
The adjustment pots are located on the main (middle)
PCB and are marked EVAC, MIC1, MIC2, MIC3.
Adjust the appropriate pot clockwise to increase
sensitivity and anti-clockwise to decrease sensitivity.
4.
Replace lid and screws and reapply power.
Optional Modules
Alert and evacuation tones are available with the
installation of the optional A 2073 tone generator.
An optional compressor/compander module (A 4426) can
be fitted internally to inputs 7 and 8. This is desirable
when using CD/DVD players as a BGM source. It
maintains a consistent output level during CD/DVD
playback to eliminate constant adjustment of volume
levels from quiet tracks to louder tracks on the disc.
TABLE 1: DIP SWITCH SETTINGS
Inputs 1 - 6 (refer to DIP 1-6)
Switch
Item
On
Off
1
Input Type
Line
Mic
2
Line Level
1V
100mV
3
Priority
On
Off
4
Phan. Pwr
On
Off
Inputs 7 - 8 (refer to DIP 7)
Switch
Item
On
Off
1
Input 8
1V
100mV
2
-
-
-
3
-
-
-
4
Input 7
1V
100mV
