Adastra A22 User manual

A22
Class-D Compact Music Amplifier
Item ref: 953.422UK
User Manual
Version 1.0
Caution: Please read this manual carefully before operating
Damage caused by misuse is not covered by the warranty

953.422UK User Manual
Introduction
Thank you for choosing the A22 to power your sound system. This compact digital amplifier
has been designed to provide a flexible background music and public address solution in a
discreet and easy-to-use format. Please read and keep this user manual to achieve the best
results from your equipment and avoid damage through misuse.
Front panel
1
Power on/off switch
5
Music TREBLE EQ control
2
Media player
6
Music BASS EQ control
3
Microphone input 6.3mm mono jack
7
AUX 1 input 3.5mm stereo jack
4
MIC VOLUME control
8
Music VOLUME control
Rear Panel
9
LINE OUT output L+R RCA
13
CH 1 speaker out +/- screw terminals
10
AUX 2 input L+R RCA
14
CH 2 speaker out +/- screw terminals
11
AUX 3 input L+R RCA
15
IEC mains power inlet and fuse holder
12
FM antenna connection F-type

953.422UK User Manual
Placement
The A22 amplifier is supplied with 4 mounting
brackets, which can be fixed to the sides of the
housing with the tab facing upwards to enable
the A22 to be mounted under a counter-top
The A22 can even be mounted against a wall.
Alternatively, the A22 may be used free standing on any flat surface or 2 units can be
mounted side-by-side in a 19”rack with one mounting bracket facing forwards at each side,
occupying a 1U rack space (the 4 self-adhesive feet will need to be removed to allow this)
Speaker connections
The A22 has 2 speaker outputs - CH1 and CH2 - on a single removable screw terminal block,
which can be wired as Left and Right stereo outputs. (13, 14)
Connect the negative “–” screw terminal to the negative “–” speaker terminal(s)
Connect the positive “+” screw terminal to the positive “+” speaker terminal(s)
Use speakers with a combined impedance no lower than 4Ωfor each output channel.
•If each speaker being connected is 4Ω, then connect only 1 speaker to each channel.
•If each speaker is 8Ω, you can connect 1 speaker or 2 speakers in parallel per channel.
•Do not connect more speakers to either channel, as this may cause damage to the A22.
An example of wiring 8Ωspeakers to the A22 is
shown opposite.
A single 8Ωspeaker may be connected to a
channel or 2 may be connected in parallel to
present a combined 4Ωload to the output.
The impedance of the load, measured in
“Ohms” (Ω), will also determine the power.
The amplifier delivers its maximum power
output at the minimum impedance rating (4Ω).
If the impedance is higher (e.g. 8Ω), then the
output from that channel will be lower.
The combined load on each output shares the
power from that amplifier channel.
This means that if two 8Ωspeakers are connected to a single output in parallel, they will each
receive half of the full power. If the amplifier is delivering 50W to two 8Ωspeakers connected
in parallel, they must each be able to handle 25W.

953.422UK User Manual
Input connections
The A22 has a 6.3mm microphone input and a media player (2) with several options for stereo
music playback, including the internal media player and 3 stereo AUX line inputs.
If a microphone is to be used for announcements, turn the MIC VOLUME control (4) down and
connect a wired microphone to the MICROPHONE jack input (3) on the front panel, using a
microphone lead terminated with a 6.3mm plug.
A smart phone, tablet or mp3 player can be connected to the AUX1 jack (3.5mm stereo) on
the front panel (7)
Likewise, other stereo audio sources, such as CD player, DAB+/FM tuner, TV or satellite
decoder may be connected via the AUX2 and AUX3 L+R RCA inputs on the rear panel (10, 11)
The 3 AUX inputs are all selected via the MODE button on the built-in media player section.
The other stereo input source options are mp3 playback from USB or microSD, FM tuner and
Bluetooth, which are all handled by the built-in media player.
For good reception of FM radio stations (if needed) in the media player, the A22 has an “F”
connector (12) on the rear panel which can be connected to an external FM antenna (aerial)
This is recommended if the FM tuner is to be used.
For mp3 playback, it is necessary to insert a USB flash drive into the USB port and/or a
microSD card into the microSD slot on the front panel. These inputs are described in more
detail in the Media Player section on the following pages.
The memory devices (USB or microSD) must be formatted to FAT32 and have standard mp3
audio files stored on them.
To link the audio output (music + microphone) of the A22 onto further equipment or as part
of a larger sound system, connect the LINE OUT (9) connectors (L+R RCA) to the left and
right line input of the additional equipment.
Once all the above connections are made, ensure that the power is switched off (1) and
connect the IEC power inlet (15) to the 230Vac mains supply, using the IEC lead provided.

953.422UK User Manual
Operation
When all connections have been made as described above, turn down the MIC VOLUME and
MASTER VOLUME control and switch on the power.
If a microphone is connected, gradually increase the MIC VOLUME whilst speaking into the
microphone until the required level is reached through the speakers.
Note: Avoid pointing the microphone towards the speakers, which may result in feedback
(loud whistling or howling caused by the microphone ‘hearing’its own output)
The A22 has an inbuilt media player section, which governs all background music and
playback options (independently of the microphone input). Full details of the media player
operation are shown overleaf.
The Media player output level is governed by the music VOLUME control (8).
The tonal character of the media player and line inputs is adjusted via the TREBLE and BASS
EQ controls (5, 6)
Turning the TREBLE control clockwise boosts the higher frequencies, whilst turning it
anticlockwise reduces the higher frequency content. Reduce the TREBLE level if there is
screeching feedback from the microphone or if playback is too thin or tinny sounding. Increase
the TREBLE level if the sound is muffled and not clear.
Turning the BASS control clockwise boosts the lower frequencies, whilst turning it
anticlockwise reduces the lower frequency content. Reduce the BASS level if there is low
howling feedback from the microphone or if playback is too boomy and distorted. Increase the
BASS level if the sound is too thin with not enough warmth or depth.
Be aware that a combination of Mic volume, Music volume, Treble and Bass all add up to drive
the amplifier and if all are turned up, this can result in overdrive (aggressive and growly or
fuzzy output) which can be damaging to connected speakers and the amplifier. Turn the
output levels down if this happens until the distorted sound becomes cleaner and clearer.
Before powering the A22 off, ensure that the volume controls are turned down to avoid loud
noises or pops through the connected speakers.

953.422UK User Manual
Media player
The media player has several different audio source
options, which are accessed using the “MODE”
button. Five more buttons control the playback (and
recording) of tracks, which is displayed in the LED
display directly below the buttons.
Below the LED display is a USB port for inserting a
flash drive (USB pen drive) and below this is a slot
for a micro SD card (or TF card)
Functions of the media player are described in the table below.
Function
Display
Description
MODE

Select front panel AUX1 input 3.5mm stereo jack

Select rear panel AUX2 input L+R RCA connectors

Select rear panel AUX3 input L+R RCA connectors

: MP3
Mp3 playback - only if USB/microSD inserted

.MHz
FM radio station –shows channel, then frequency

Bluetooth mode
REPEAT

Repeat single track

Repeat all tracks in the current folder

Play all tracks in random order

Repeat all tracks on media
REC
: 
Hold REPEAT for 5 seconds in AUX or FM modes to
record to USB or SD (if no USB) press pause to stop.
Note: cannot record from BT / USB / microSD
EQ

EQ1 = POP

EQ2 = CLASSICAL

EQ3 = ROCK

EQ4 = JAZZ

Normal output –no additional EQ


Previous track or FM channel (station)
►
 (paused mp3)
Play or pause the current track (USB/SD/Bluetooth)


Next track or FM channel (station)

953.422UK User Manual
Remote control
The A22 is supplied with a handheld infra-red remote control, which shares many of the front
panel functions along with some additional controls, as described below.
Media player power on/standby button
Repeat mode –select Random, One, Folder or All tracks
MODE
Select USB, SD, FM tuner or Bluetooth mode
CH- / CH+
Select FM radio station
EQ
Select EQ –Bass, Pop, Rock, Jazz, Classical or Normal
/ 
Previous or Next track select

Play / Pause track (auto-tune in FM tuner mode)
/ 
Adjust media player volume down or up
0 - 9
Direct track or channel access –key in track number
Bluetooth connection
The Bluetooth function allows connection of a smart phone or tablet to the media player
section for playback of stored files or streamed digital audio. To enable this function, it will be
necessary to pair the sending device to the receiver as follows.
1. Press the media player MODE button until the display shows “”
2. Open the Bluetooth settings menu on the smart phone or tablet
3. Scan for Bluetooth devices and look for “A22” in the list of available devices
(ensure that the A22 is powered on with Bluetooth selected and within reception range)
4. Select “A22” and the sending device should confirm that it is connected as an audio
device.
5. Play audio from the sending device, ensuring that volume controls are not turned down
or muted
If the sending device goes out of range, connection will only resume when back in range.
Likewise, if a different mode is selected, connection should resume when Bluetooth mode is
re-selected.
If Bluetooth is disabled on the sending device or paired to a different receiver, it will be
necessary to re-connect the sending device to the A2 from step 2 above to re-establish a
Bluetooth link.

953.422UK User Manual
Specifications
Power supply
230Vac, 50Hz (IEC)
Output impedance
4 - 8 Ohms (each channel)
Output power: 8 Ohms
2 x 25W rms / 2 x 40W max. (@ 1kHz 10% THD)
Output power: 4 Ohms
2 x 35W rms / 2 x 55W max. (@ 1kHz 10% THD)
Inputs: line
Aux 1 (3.5mm), Aux 2 (L+R RCA), Aux 3 (L+R RCA)
Input: mic
6.3mm jack
Controls
Mic Volume, Treble, Bass, Music Volume
Audio source
USB/microSD player, FM tuner, Bluetooth
Antenna connection
F-type (FM tuner)
Dimensions
215 x 180 x 43mm
Weight
820g
Disposal: The “Crossed Wheelie Bin” symbol on the product means that the product is classed as
Electrical or Electronic equipment and should not be disposed with other household or commercial waste
at the end of its useful life. The goods must be disposed of according to your local council guidelines.
Hereby, AVSL Group Ltd. declares that the radio equipment type 953.422UK is in compliance with Directive 2014/53/EU
The full text of the EU declaration of conformity is available at the following internet address:
http://www.avsl.com/assets/doc/9/5/953422UK.pdf
Errors and omissions excepted. Copyright© 2020. AVSL Group Ltd.
Unit 2-4 Bridgewater Park, Taylor Rd. Manchester. M41 7JQ