Redback A 4205 User manual

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Redback® A 4205 Kiosk Loop Amplier
User manual revision number: 1.0 24/02/2020
Operating Manual
A 4205 3VA Hearing Induction Loop Amplier
Redback® Proudly Made In Australia
Distributed by Altronic Distributors Pty. Ltd.
Phone: [phone] Fax: [phone] Internet: www.altronics.com.au
IMPORTANT NOTE:
Please read these instructions carefully from front to back prior to installation.
They include important setup instructions.
Failure to follow these instructions may prevent the amplier from working as designed.

Redback® A 4205 Kiosk Loop Amplier
www.redbackaudio.com.au
Redback® Proudly Made In Australia2
1.0 INTRODUCTION
Induction Loop ampliers, also known as T-loop or Hearing Loop ampliers, are installed to greatly enhance the listening
experience of people using hearing aids. The hearing loop, as its name suggests, is basically a loop of wire which
surrounds a designated area to transmit audio to a hearing aid. An audio source is fed into the Amplier, and the output
of the amplier then sends a high current signal into the loop, which generates a magnetic eld. The magnetic eld is
then picked up by the Telecoil inside a hearing aid.
Hearing Loops are commonly installed in public areas which are generally noisy, making it difcult for hearing impaired
users to hear clearly. The A 4205 amplier model has been engineered to meet AS60118.4-2007 and includes a compres-
sor/limiter circuit with tailored frequency response ensuring excellent speech intelligibility. It will operate into loads of less
than 2 ohms and is short circuit proof.
The amplier is ideally suited for small installations such as ticket booths, information desks, emergency room interview
windows, reception desks etc and has a coverage up to about 1m.
The A 4205 3VA model delivers 0.3A RMS, 0.35 Amps peak into a typical Loop Resistance of 0.2Ω to 1.7Ω (max 2Ω).
Inputs are provided for 3 pin XLR balanced mic with phantom power and a dual auxiliary input. The unit is powered from
12V DC (plugpack supplied).
2.0 FRONT PANEL GUIDE
Figure 1 shows the layout of the front panel.
Fig 1
1 Mic volume control 2 Signal Presence Indicator 3 Aux volume control
4 VU Indicator 5 On Indicator 6 Power Switch
4.0 REAR PANEL CONNECTIONS
Figure 2 shows the layout of the rear panel.
Fig 2
1 DC Fuse (800mA)
This fuse protects the amplier.
2 12V DC Input
Connect 12V DC to either of these inputs. A 12V DC plugpack is supplied for connection to the 2.1mm socket.
Timer
Power
On
0
2
46
8
10
Mic Aux
Signal
Present
0dB-3dB
-6dB
-9dB
0
2
46
8
10
Timer
3VA Loop Amplier
A 4205
123 4 56
L
R
Mic Input
+
OUTPUT
_
Aux input
+
-
Made in Australia by
Altronic Distributors
Pty Ltd
www.redbackaudio.com.au
12VDC
Input
+
12V DC
Input
_
DC Fuse
2 1
3
1 2 3 4 5 6

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Redback® A 4205 Kiosk Loop Amplier
3 Output Connections
Connect the output loop to these terminals. The polarity is not important.
4 Headphone Output
Use this 3.5mm connector to connect a set of headphones to listen to the audio output of the amplier.
5 Aux Input
The AUX inputs are dual RCA connectors which are internally mixed to produce a mono input signal.
6 Mic Input
A 3 pin balanced Microphone level input.
Phantom power (12V DC) is also available on this input. To activate the phantom power, rst remove the lid.
Inside there is a 3 pin header labelled JP1. Move the shunt header to the “ON” position. Phantom power is now
enabled.
5.0 SETUP GUIDE
The A 4205 loop amplier has a balanced 3 Pin female XLR Microphone input and a dual RCA Aux input.
The Microphone input has an input sensitivity of 3mV and will overload at 50mV. The aux input has an input sensitivity of
300mV and will overload at 1V. Phantom power (12V DC) is available at the Mic input.
The unit is powered from 12V DC either by the supplied plugpack or another 12V DC source.
The hearing loop, as its name suggests, is basically a loop of wire which surrounds a designated area to transmit audio to
a hearing aid. The recommended length of the loop for use with the A 4205 loop amplier is around 3.5 metres in length
with a resistance of between 0.2 and 1.7 (Max 2). For best results we recommend two turns of 0.4 enamelled copper
wire (Altronics W 0404) or two turns of 7/0.16 Tinned Light Duty Hook Up Cable (Altronics W 2250 series of cable).
Depending on the application this loop can be laid out in a rectagular shape 1.0m x 0.75m or 1.1m x 0.7m etc, as long as
the total length is around 3.5m (refer to gure 3 for more details).
Fig 3.0 illustrates the input connections and loop details.
Fig 3
L
R
Mic Input
+
OUTPUT
_
Aux input
+
-
Made in Australia by
Altronic Distributors
Pty Ltd
www.redbackaudio.com.au
12VDC
Input
+
12V DC
Input
_
DC Fuse
2 1
3
LOOP DETAILS:
LOOP RESISTANCE (0.2Ω TO 1.7Ω. MAX 2Ω)
LOOP LENGTH ≈ 3.5 metres
For best results we recommend two
turns of 0.4 enamelled copper wire
(Altronics W 0404) or two turns of
7/0.16 Tinned Light Duty Hook Up
Cable (Altronics W 2250 series of cable).
Each turn is to be around 3.5m in length,
twist together the two loop cable ends
and either screw directly into the output
ends.
Turn 1
Turn 2
1.0m
0.75m 0.75m
1.0m
Twist together
Twist together
CD
REDBACK

Redback® A 4205 Kiosk Loop Amplier
www.redbackaudio.com.au
Redback® Proudly Made In Australia4
5.0 TYPICAL INSTALL
The A 4205 loop amplier is designed to work with small installs where the coverage required is around 1m. It is ideal
for ticket booths, reception desks, information booths etc. The loop can be installed in a vertical axis such as illustrated in
gure 4 where the loop is attached to the back of the interview screen. A preferred installation is shown in gure 5 which
provides a loop which works on both the vertical and horizontal axis. In both installs the loop length is around 3.5m in
total with a total resistance of 0.2Ω to 1.7Ω (max 2Ω). Twist together the tail wires that don’t form part of the loop.
Fig 4. Loop is installed on the back of the interview screen on the vertical axis.
Fig 5. Loop is installed under the desk on both the vertical and horizontal axis.
Twist these tail wires together.
Loop
Twist these tail wires together.
Loop