Keene Electronics KLABXB Operational manual
Installation & Connection
Installation should only be carried out by a qualified installer or electrician, as a certain amount of
electrical knowledge is assumed.
Mounting
The 25mm depth will allow installation into standard UK 2-gang boxes, which may be galvanised
metal for installation in solid walls, or plastic drylining (with lugs) or surface mount box or trunking
system.
Wiring
In order to make a reliable and safe connection without short circuits it is recommended that the
speaker cables are prepared and tinned prior to connection, with no more than approx 7mm of
tinned wire extending out of the insulation. The speaker connectors are a push fit onto the PCB and
can be easily removed and refitted to aid installation.
Power
The amplifier requires a power supply of 12v to 18v DC centre positive and a minimum current of
3500mA. If you are not using the recommended psu please verify that the supply is correct BEFORE
connection. If using the recommended supply we suggest that it is connected in accordance with
current wiring regulations. The amplifier can also be powered from a 12v car battery but NOT
directly from a car battery charger as this would damage the circuitry. Do not install near any heat
sources such as radiators, stoves, or other apparatus that produce heat. The mains connection
should be via a fused and switched mains outlet such as order code SWL1.
Environment
The KLABXB is not IP rated for use in damp environments but if due care is given to positioning of
the amplifier and supply then it can be used in zone 3 installations. Please use a qualified electrician
operating to current regulations if you intend to use this unit in a bathroom.
Overview
Easily add music to your kitchen, bedroom, study, bathroom etc.
This tiny wall mount amplifier fits into a standard UK two gang
pattress and provides a powerful 20W RMS per channel. In
operation it really couldn't be any easier. When you want to use
it simply connect via Bluetooth and control the volume via your
bluetooth device. When you disconnect or stop streaming the
amplifier automatically switches into very low power standby
mode. Whenever you connect again it instantly wakes again up
to deliver clear powerful audio.
IMPORTANT - Please Read!!!
As supplied the left and right edges of the front panel label can be
flexed outward to allow access to the panel fixing screws. Once
fastened in position and tested(!) the backing paper can be peeled off
and the sides fixed down flush to conceal the screws. ONLY perform
this operation once the installation has been tested and found to be
satisfactory. Once stuck down this label cannot be removed without
damage.
Replacement front panels are available, (part number KLABXBSFP)
Loudspeakers
Connect the loudspeakers being careful to keep both left and right phase connections the same. The loudspeaker
screw terminal connectors are a push fit onto the PCB and can be easily removed for ease of installation. Please
note that the amplifier is fully bridged so there is NOT a common ground or return connection. The recommended
minimum speaker impedance is 4 ohms on each channel. If driving 2 speakers or more on each channel use them
in series if they are both 4 ohms or in parallel if they are both 8 ohms. Note the speaker corresponding to the left
input is actually on the right hand terminals in the amp as viewed from the front.
Mono audio selector
This jumper is left off by default. If fitted the left and right audio channels will be commoned together and the left
and right channel speaker outputs will be identical mono.
Left and Right channel trim adjustment - important!
These adjust the signal level and will determine how loud (or quiet) the amplifier will be in use. The KLABXB works
as a slave amplifier so the volume can only be controlled by the bluetooth device. Usually the source device will be
a mobile phone or tablet with the volume increased or decreased by a small percentage with a keypress. It is
particularly worth checking that the minimum volume level (as set by your device) corresponds to the lowest level of
background music that you find comfortable. The KLABXB is very powerful and it is rare that the maximum volume
would be found insufficient. These trimmers provide a wide range of adjustment from fully clockwise maximum
volume (no attenuation) to minimum volume when fully anticlockwise. Please do take the time to check the volume
levels are as desired before finally fastening the front panel.
More notes on volume control
We have found that some Android devices connect to Bluetooth amplifiers with their initial volume at near maximum
volume. There is an App available from the Play store called “A2DP Volume” that seeks to remedy this annoyance.
We found this to work quite well but we have no affiliation and there may well be other Apps that provide a similar
function.
Bluetooth ID
DC input
12-18v
3500mA
Bluetooth ID
selectors
Mono audio
selector
Left
speaker
connection
Right
speaker
connection
Connections for Power and Loudspeaker Outputs are located on the rear of the PCB.
Reserved for
programming
Left and Right
channel level
trimmers
Jumper 1 Jumper 2 Jumper 4
On On On (factory default)
Off On On
On Off On
Off Off On
Bluetooth ID
KeeneExp0
KeeneExp1
KeeneExp2
KeeneExp3
On On Off KeeneExp4
On Off Off KeeneExp6
Off Off Off KeeneExp7
Off On Off KeeneExp5
BT name
1 2 4
The KLABXB is supplied with jumper connectors fitted
to all three headers as default, giving it the Bluetooth
ID of KeeneExp0. The name can be altered by
removing one or more of these jumpers as listed in
this table. In the example below the Bluetooth ID
would be KeeneExp4
This adjustment MUST be made before the power supply is connected otherwise it will have no effect.
Power output (15v supply): 20W RMS per channel into 4ohms
Total Harmonic Distortion + Noise: 0.15%
(4ohm load, 1KHz, 8W power)
Bandwidth: 20Hz to 22KHz Passive limitation built in
Power Supply: 12V to 18V (absolute max 18V DC) minimum current 3.0A.
Connection via a 2.1mm DC connector centre positive, auto mute on
under voltage.
Fuse: self resetting 3A built in – to clear remove power for at least 20
seconds, clear fault and reconnect
Amplifier topology: full bridge mode all speaker connections are live ( no common ground
connection)
Recommended min speaker impedance: 4 ohms per channel
Absolute minimum speaker impedance: 3 ohms per channel
SNR: 98dB
Voltage gain: 33dB
Input required to produce full output: approx 775mV
Power output (12v supply): 15W RMS per channel into 4ohms
Standby current 20mA (0.3W at 15v supply)
Bluetooth Audio Modes A2DP Codecs: SBC, MPEG1,2 audio / mpeg2,4 AAC /ATRAC /APTX
Specifications:
Installation and Operation
Double check all connections and fasten the panel into the mounting box (do not fasten the label at this
stage. Switch on the power source and observe the LED's. If all is well then the blue LED should begin
flashing. Search for Bluetooth devices and you should find “KeeneExp0” unless you have changed this from
the factory default. Connect to this device and the LED will stop flashing and change to steady blue. If you
are asked for a pairing code enter 0000. When successfully connected you should be able to hear your
music via the connected loudspeakers. The Amplifier will stay connected unless you disconnect, move your
device out of range, switch bluetooth off or pair to another Bluetooth device. If you do move your device out
of range you will need to reconnect again.
When the KLABXB has no active connection the led will start to flash blue for approximately 20 seconds. If
no connection is established the KLABXB will then switch off the amplifier circuit and enter a low power
standby mode indicated by the red LED. As soon as a Bluetooth connection is established it will
automatically switch back to normal operation.
Part numbers you may find useful:
Architectural Wall/Ceiling mount loudspeakers
5 1/4" 25W [CMS5U]
8" 30W [CMS8U]
Switched Spur outlet
An MK style switched fused spur outlet, ideal for making a safe connection to the power supply.
[SWL1]
Power supply (input: 100-240v AC, Output: 15v DC 4.0A)
[KLABPSU]
Replacement front Fascia panel
[KLABXBSFP]
Loudspeaker cable 42 strand OFC (per metre)
[KBL31]
Old Hall Mills Business Park Little Eaton Derbyshire DE21 5EJ
Telephone 01332 830550 Fax 01332 830551
http://www.keene.co.uk
http://www.keene-electronics.co.uk
OEM Custom Build Options
This product can be manufactured with custom printed front panels and with custom Bluetooth IDs if
required. It is usually uneconomical to manufacture less than 50pcs at a time in this manner but please get
in touch if you have such a requirement.
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