Bosch PLENA Series User manual

PLENA Mixer amplifier, 4‑zone, 240W
PLE‑4MA240‑CN
en Operation manual

PLENA Mixer amplifier, 4-zone, 240W Table of contents | en 3
Bosch Security Systems B.V. Operation manual 2019-03 | V1.1 |
Table of contents
1Safety 4
2About this manual 5
2.1 Manual purpose 5
2.2 Digital document 5
2.3 Intended audience 5
2.4 Alerts and notice signs 5
2.5 Conversion tables 5
2.6 Copyright and disclaimer 6
2.7 Document history 6
3Introduction 7
3.1 The PLENA product range 7
3.2 Parts included 7
3.3 The PLENA Mixer amplifier 7
3.4 Controls, connectors and indicators 9
3.4.1 Front panel 9
3.4.2 Rear panel 10
4Installation 11
4.1 Unpack unit 11
4.2 Install unit in 19" rack (optional) 11
4.3 Check settings/configurations 11
4.4 Connect unit to mains 11
5Connections 12
5.1 Connecting inputs 12
5.1.1 Priority microphone (input 1) 12
5.1.2 Additional microphones (inputs 2 and 3) 12
5.1.3 Emergency inputs 12
5.1.4 Music source inputs 13
5.2 Connecting outputs 13
5.2.1 Connecting loudspeakers 13
6Configuration 14
6.1 Unit settings 14
6.1.1 Rear panel settings 14
6.1.2 Pin settings and labeling 15
7Operation 17
7.1 Switching on and off 17
7.2 Microphone control 17
7.3 Music control 17
7.3.1 Source selection 17
7.3.2 Volume control 17
7.4 Tone control 17
7.5 Output control 17
7.5.1 Zone selection 17
7.5.2 Master volume control 18
8Troubleshooting 19
8.1 Customer service 19
9Maintenance 20
10 Technical data 21

4en | Safety PLENA Mixer amplifier, 4-zone, 240W
2019-03 | V1.1 | Operation manual Bosch Security Systems B.V.
1 Safety
Prior to installing or operating products, always read the Important Safety Instructions which
are available as a separate multilingual document: Important Safety Instructions (Safety_ML).
These instructions are supplied together with all equipment that can be connected to the
mains supply.
Safety precautions
The PLENA Mixer amplifier is designed to be connected to the public distribution network.
– To avoid any risk of electric shock, all interventions must be carried out with
disconnected mains supply.
– The ventilation should not be impeded by covering the ventilation openings with items
such as newspapers, table cloths or curtains.
– Connection of external wiring to this equipment requires installation by qualified
personnel only.
– The operation must only be performed by qualified personnel.
– Use the apparatus in moderate climate.
!
Caution!
These service instructions are for use by qualified service personnel only.
To reduce the risk of electric shock, do not perform any servicing other than that contained in
the operating instructions unless you are qualified to do so.

PLENA Mixer amplifier, 4-zone, 240W About this manual | en 5
Bosch Security Systems B.V. Operation manual 2019-03 | V1.1 |
2 About this manual
Please read this manual carefully before installing and operating the PLENA Mixer amplifier
and retain it for future reference.
2.1 Manual purpose
The purpose of this manual is to provide information required for installing, configuring and
operating a PLENA Mixer amplifier.
2.2 Digital document
This manual is available as a digital document in the Adobe Portable Document Format (PDF).
Refer to the product related information at: www.boschsecurity.com.
2.3 Intended audience
This manual is intended for installers and users of a PLENA system.
2.4 Alerts and notice signs
Four types of signs can be used in this manual. The type is closely related to the effect that
may be caused if it is not observed. These signs - from least severe effect to most severe
effect - are:
Notice!
Containing additional information. Usually, not observing a ‘notice’ does not result in damage
to the equipment or personal injuries.
!
Caution!
The equipment or the property can be damaged, or persons can be lightly injured if the alert
is not observed.
!
Warning!
The equipment or the property can be seriously damaged, or persons can be severely injured
if the alert is not observed.
Danger!
Not observing the alert can lead to severe injuries or death.
2.5 Conversion tables
In this manual, SI units are used to express lengths, masses, temperatures etc. These can be
converted to non-metric units using the information provided below.
1 in = 25.4 mm 1 mm = 0.03937 in
1 in = 2.54 cm 1 cm = 0.3937 in
1 ft = 0.3048 m 1 m = 3.281 ft
1 mi = 1.609 km 1 km = 0.622 mi
Tab.2.1: Conversion of units of length

6en | About this manual PLENA Mixer amplifier, 4-zone, 240W
2019-03 | V1.1 | Operation manual Bosch Security Systems B.V.
1 lb = 0.4536 kg 1 kg = 2.2046 lb
Tab.2.2: Conversion of units of mass
1 psi = 68.95 hPa 1 hPa = 0.0145 psi
Tab.2.3: Conversion of units of pressure
Notice!
1 hPa = 1 mbar
°F = _. °C + 32
9
5
°C = _. (°F - 32)
5
9
°F = 9/5 (°C + 32) °C = 5/9 (°F - 32)
Tab.2.4: Conversion of units of temperature
2.6 Copyright and disclaimer
All rights reserved. No part of this document may be reproduced or transmitted in any form by
any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior
written permission of the publisher. For information on getting permission for reprints and
excerpts, contact Bosch Security Systems B.V..
The content and illustrations are subject to change without prior notice.
2.7 Document history
Release date Documentation version Reason
2018.11 V1.0 1st edition.

PLENA Mixer amplifier, 4-zone, 240W Introduction | en 7
Bosch Security Systems B.V. Operation manual 2019-03 | V1.1 |
3 Introduction
3.1 The PLENA product range
The PLENA Mixer amplifier is part of the PLENA product range. PLENA provides public address
solutions for places where people gather to work, worship, trade, or relax. It is a family of
system elements that are combined to create commercial audio systems tailored for virtually
any application.
The PLENA product range includes:
– mixers
– preamplifiers
– power amplifiers
– a music source unit
– digital message manager
– a feedback suppressor
– call stations
– an All-in-One system
– a voice alarm system
– a timer
– a charger
– a loop amplifier.
The various elements are designed to complement each other thanks to matched acoustical,
electrical and mechanical specifications.
3.2 Parts included
Quantity Component
1 PLE-4MA240-CN PLENA Mixer amplifier
1 Power cord
1 Set of 19”mounting brackets
1 Manual
1 Important safety instructions
3.3 The PLENA Mixer amplifier
The PLENA Mixer amplifier is a high performance 4-zone mixer amplifier, built on energy
efficient class-D technology. Three selectable music sources, including a front panel 3.5mm
input for hand-held device connection, provide flexibility for background music source.
Multiple levels of priorities and ducking of music make this amplifier an excellent choice for
background music and business paging.
One microphone input (Input 1) can be switched between microphone level and line level
sensitivity. The other two microphone inputs can be connected with XLR or TRS type
connectors. Phantom power can be switched on to provide power to condenser microphones.

8en | Introduction PLENA Mixer amplifier, 4-zone, 240W
2019-03 | V1.1 | Operation manual Bosch Security Systems B.V.
Input 1 can take priority over all other microphone and music inputs: Input 1 priority can be
activated by contact closure on the PTT (push to talk). A 2-tone chime can be configured to
precede an announcement.
The volume of each microphone input can be individually adjusted to obtain the required mix;
the mixed output is controlled via the master volume control and separate high/low tone
controls.
Separate music inputs are available with their own input selector and volume control. The user
can choose a music source like a CD/DVD player or radio (like the PLE-SDT), and set the level
of music. A front panel music input makes it easier to connect a hand-held device as music
source.
A telephone / 100V emergency input is provided for easy integration with a telephone paging
system or another Public Address system. It has its own preset volume control and overrides
all other inputs, including input 1.
The unit also provides a 24V DC output to override remote loudspeaker volume control
whenever there is a telephone or emergency input signal.
The unit has a line output to add amplifiers for larger systems with more output power.
Users can create custom labels for inputs, music sources, and output zones. These labels can
be attached to the special holders at the front of the mixer amplifier. Colored pins can also be
inserted at various positions around the volume and tone controls to indicate favorite settings
for a particular application.
An LED VU meter monitors the master output. A headphone socket, below the VU meter,
provides the mixer output. For total reliability and ease of use, a limiter is integrated into the
output stage to restrict output if the user applies too much signal.
For a schematic overview of the PLENA Mixer amplifier, see figure 3.1.
EMERGENCY
-
+
VOX
-
+
PTT DETECT
24V
PH-24V
MIC/LINE1
EMG-VOX
GAIN
MIC1-TR
PH SWITCH
-
+
MIC2
SOURCE-SELECT
AUX 1
-
+
MIC3
GAIN
DUCKING
CLASS D
LIMITER
CLASS D CTRL
B+
-
+
CHIME
LINE OUT
ZONE 1~4
MONITOR
VU-METER
MUTE
AUX 2
RELAY
I2C
100V
MIC1/LINE
MIC2
MIC3
AUX
BASS
TREBLE
MASTER VR
Micro
controller
TEL-EMG/MIX
SELECT
LINE-OUT
MUTE
ZONE1~4
AUX1~3
PRIO
CHIME ON/OFF
B+ (50VDC/6A)
+5VDC/1A
+28VDC/1A
SMPS
B+ ON/OFF
+24VDC/500mA
+28VDC
LDO
+3V3/250mA
+5VDC
LDO
+9VDC/100mA
230VAC EMC
24VDC/100mA SUPPLY
24V-PRIO
+24VDC
+24VDC
ZONE1~4 BUTTON
SOURCE BUTTON
FILTER
MIC/LINE
SWITCH
DUCKING
GAIN
ZONE CONTROL
TONE
CONTROL
BASS
TREBLE
MASTER
GAIN
SPI
I2C EEPROM
-
+
ADC
ATTN
AUX 3
24V
PH-24V
PH SWITCH
24V
PH-24V PH SWITCH
Figure3.1: Schematic overview of PLE-4MA240-CN

PLENA Mixer amplifier, 4-zone, 240W Introduction | en 9
Bosch Security Systems B.V. Operation manual 2019-03 | V1.1 |
3.4 Controls, connectors and indicators
3.4.1 Front panel
Number Description
1 Power button, with power-on LED.
2 Label holder for user-defined description of microphone/line 1 and microphone
2 and 3 inputs. Custom labels can be created by user.
3 Label holder for user-defined description of music sources (Aux 1, 2 and 3).
Custom labels can be created by user.
4 High tone (treble) control knob for mixed output.
5 Label holder for user-defined description of zone names. Custom labels can be
created by user.
6 Master volume control knob. It controls all inputs except emergency.
7 LED VU meter for master output, with LEDs for -18, -12 -6, -3, 0 dB.
8 Input level control knobs for:
• microphone/line 1
• microphone 2
• microphone 3.
9 Music source selector (for Aux inputs 1, 2, and 3). Selected Aux input LED
switches on (green), unselected Aux input LEDs remain off.
10 Aux-3: Music input with 3.5 mm mini-TRS connector for a music source like a
mobile phone or laptop. Stereo signals are converted into mono.
11 Volume control knob for selected music source input.
12 Low tone (bass) control knob for mixed output.
13-16 Zone 1 to 4 selection buttons with LED indicator.
17 Headphone socket.

10 en | Introduction PLENA Mixer amplifier, 4-zone, 240W
2019-03 | V1.1 | Operation manual Bosch Security Systems B.V.
3.4.2 Rear panel
-
1 2 3 4 10 125 6 7 8 9 11
13
0
Emergency/Telephone Rated input power 360W
Cal l
Duck in g
L
R
Aux2
Aux1
+
-
Gnd
Line O ut
Z1 Z2 Z3 Z4
24V
DC out
Prio ri ty
0100V
+0100V0100V0100VT4.
0
L 25 0V
23 022 0 -V~5 Hz
Gnd
Number Description
1 Telephone / 100V emergency input volume control knob - from -20 dB to 0 dB.
2 Telephone / 100V emergency input, with Euro style pluggable screw terminal
connector. This input has the highest priority amongst all inputs.
100V emergency input shall be connected to pins marked as 100V and 0V;
telephone signal (through coupler) shall be connected to +,Gnd, -.
3 DIP switch for microphone/line 1 with selection for: line/mic level, chime tone
on/off, phantom power (24V), and PTT (push to talk).
4 Microphone/line 1 input, with 5-pin Euro style pluggable screw terminal
connector. Balanced mic/line input (3 pins), remaining 2 pins for trigger input, if
these two pins are not connected this input will be mixed with other inputs
without priority.
5 Microphone 2 input, with combo (XLR +TRS) balanced signal input connector.
6 DIP switch for microphone 2 and 3 with selection for phantom power (18VDC).
7 Microphone 3 input, with combo (XLR +TRS) balanced signal input connector.
8 Ducking level control knob for microphone/line 1 input. It sets the required BGM
(background music) level when trigger (PTT) is active.
9 Aux-1 and 2: Music inputs with Cinch connector for a music source like a CD/DVD
player or radio. Stereo signals are converted into mono.
10 Line-out: Balanced line-level output (nominal level: 1V) for system expansion,
with 3-pin Euro style pluggable screw terminal connector.
11 Loudspeaker outputs:
– Zone 1 to 4 outputs, Euro style pluggable screw terminal connector - 100 V.
– 24V DC output for loudspeaker volume control override. It is activated when
there is a telephone or emergency input signal.
12 Earth connection screw.
13 Mains connector (3-pole) with fuse inside.
Notice!
The unit must be earthed.

PLENA Mixer amplifier, 4-zone, 240W Installation | en 11
Bosch Security Systems B.V. Operation manual 2019-03 | V1.1 |
4 Installation
4.1 Unpack unit
1. Remove the unit from the box, and discard the packaging material according to local
regulations.
2. Use your fingernails to carefully peel off the protective plastic film from the label holders.
Do not use sharp or pointed objects.
4.2 Install unit in 19" rack (optional)
The PLENA Mixer amplifier is intended for tabletop use or installation in a 19"rack (see figure
4.1).
If you install the unit in a 19"rack:
– Ensure that it does not exceed the overheating temperature (+45°C ambient).
– Use the included Bosch 19” mounting brackets.
– Remove the 4 feet from the bottom of the unit.
Figure4.1: 19” bracket and rack mounting
4.3 Check settings/configurations
1. Connect any additional equipment (see Connecting inputs, page 12, and Connecting
outputs, page 13).
2. Check the settings (see Configuration, page 14).
4.4 Connect unit to mains
1. Make sure the power switch, on the front of the unit, is set to Off.
2. Connect the power cord to the mains connector and plug it into the mains outlet.

12 en | Connections PLENA Mixer amplifier, 4-zone, 240W
2019-03 | V1.1 | Operation manual Bosch Security Systems B.V.
5 Connections
5.1 Connecting inputs
5.1.1 Priority microphone (input 1)
The priority microphone (or a generic call station) that can be used with push to talk (PTT)
should be connected to microphone/line 1 input. The PTT mode can be activated by setting
the DIP switch (3) at the rear of the unit. Microphone/line 1 input has priority over all other
microphone and music inputs.
If, however, the telephone / 100V emergency input receives a signal, all inputs including
microphone/line 1 input will be overridden.
The microphone/line 1 input has a 5-pin Euro style pluggable screw terminal connector, the
first 3 pins for a balanced mic/line input, the remaining 2 pins for a trigger input. If these two
pins are not connected, this input will be mixed with other inputs without priority.
Set the DIP switch settings next to the Euro connector for microphone/line 1, as required. See
Unit settings, page 14.
Notice!
When connecting an unbalanced line level (200 mV) signal to the microphone/line input,
connect it as follows: Signal to pin 2, pin 1 and pin 3 to ground.
5.1.2 Additional microphones (inputs 2 and 3)
Additional microphones can be connected to microphone input 2 and 3 with XLR or TRS type
connectors. These microphones will mix with the background music. Phantom power can be
switched on to provide power to condenser microphones.
The telephone / 100V emergency input and microphone/line input 1 have priority over
microphone inputs 2 and 3.
5.1.3 Emergency inputs
The telephone / 100V emergency input is used for receiving emergency announcements from a
Public Address or telephone system. This input has absolute priority, and will override all
inputs when an emergency announcement or telephone signal is received.
Either a telephone line or a 100 V input signal can be connected to the Euro style pluggable
screw terminal connector (2) at the rear of the unit.
To adjust the volume of the emergency announcement or signal, turn the rotary knob (1) at
the rear of the unit. For safety reasons, the volume of the emergency announcement or signal
cannot be set to zero.
The master volume control setting (6) does not influence the volume setting of the emergency
announcement or signal.

PLENA Mixer amplifier, 4-zone, 240W Connections | en 13
Bosch Security Systems B.V. Operation manual 2019-03 | V1.1 |
!
Caution!
A connection to a telephone network must always be made via a telephone coupler that
provides adequate isolation between the telephone network (PBX) and the PLENA system.
The telephone coupler must also meet all relevant requirements for this type of
communication equipment as imposed by law and/or responsible telecommunication
organizations in the country of use. Never try to make a direct connection between the
telephone network and the mixer amplifier.
5.1.4 Music source inputs
When using a CD player, tuner or other auxiliary device for background music, connect the
line-out connectors of the music source to the appropriate line-in connectors of the mixer
amplifier. The unit has three music source inputs:
– two stereo Cinch inputs (Aux 1 and Aux 2) on the rear panel for music from an installed
device like a CD/DVD player or radio
– one 3.5mm stereo mini-jack input (Aux 3) on the front panel for music from mobile
devices like a mobile phone or laptop.
5.2 Connecting outputs
5.2.1 Connecting loudspeakers
The mixer amplifier can drive 100 V constant voltage loudspeakers.
Connect loudspeakers to the 100 V terminal on the Euro style pluggable screw terminal
connector (11) of zones 1, 2, 3 and/or 4 at the rear of the unit.
Connect the loudspeakers in parallel and check the loudspeaker polarity for in-phase
connection. The summed loudspeaker power should not exceed the rated amplifier output
power.
D
Figure5.1: Connecting loudspeakers

14 en | Configuration PLENA Mixer amplifier, 4-zone, 240W
2019-03 | V1.1 | Operation manual Bosch Security Systems B.V.
6 Configuration
6.1 Unit settings
6.1.1 Rear panel settings
The unit can be quickly set-up for operation by setting the following controls at the rear of the
unit:
– DIP switches
Default settings: mic/line-1: mic, chime: on, phantom power: on, PTT: on.
– Rotary knobs
Default settings: ducking: max (mute), telephone/emergency: max.
See the following tables for an overview of the settings and typical examples of their use.
DIP switch On Off Typical example
Line
(mic/line-1)
Input signal from line. Input signal from
microphone.
Depends on set-up.
Chime (mic/line-1) Chime will be
sounded at the
beginning of an
announcement.
Chime will not be
sounded at the
beginning of an
announcement.
Use a chime to attract
listener's attention
before making an
announcement.
Phantom power
(mic/line-1, mic-2,
mic-3)
Provides power to
condenser
microphones.
Phantom power
unavailable.
Enable phantom
power if you use
electret or condenser
microphones.
PTT “Push to
talk” (mic/line 1)
When the Push to talk
contact is closed (for
example, by pressing
the PTT button of
PLE-1CS call station):
• this input is
available for speech.
• a chime will sound,
if selected.
• the music and other
mic inputs will be
reduced in volume to
the level set by the
ducking level control
knob.
Mic/line-1 input will
mix with the
background music or
the other
microphones in the
selected zones.
Live broadcast with
PTT on will override
all other audio inputs,
except the emergency
input.

PLENA Mixer amplifier, 4-zone, 240W Configuration | en 15
Bosch Security Systems B.V. Operation manual 2019-03 | V1.1 |
Rotary knob Effect Typical example
Ducking level control Sets the required ducking
level when Push to talk is
active (see table 6.5). When
the ducking level is set to
max (mute), the music
volume will be fully
attenuated; when the ducking
level is set to mix, both music
and speech inputs can be
heard.
Set the ducking level control
to mute or attenuate the
background music when an
announcement is being made.
Telephone / 100V emergency
input volume control
Attenuates the emergency
announcement or signal.
Control range from -20dB to
0dB. For safety reasons, the
volume of the emergency
announcement or signal
cannot be fully set to zero.
Set the volume of the
emergency announcement to
a higher level when the
system is being used in large
open areas.
Notice!
When PTT is selected, the ducking control ranges between 0dB attenuation (very little
ducking) to -∞dB (muted). Ducking also impacts the music level in the unselected zone(s).
6.1.2 Pin settings and labeling
Users can create custom labels for the microphone/line inputs, description of the music
sources, and audio output zones 1 to 4. These labels can be attached to the mixer amplifier at
position numbers 2, 3, and 5 (see Front panel, page 9). Colored pins can also be inserted at
various positions around control knobs to indicate the favorite settings for a particular
application.
The pins are engineered in such a way that they cannot be taken out by hand. This is to
prevent tampering. The pins are intended to be inserted once, during installation of the unit.
The silver pins should be used to indicate the preferred settings of the unit. The red pins can
optionally be used to indicate the maximum setting of a knob.
If these settings have to be changed, use a pair of soft-tipped pliers to carefully remove the
pins. If you do not have a pair of soft-tipped pliers, you can use ordinary pliers instead, but
first place some plastic tape on the tips of the pliers to prevent damaging the front of the unit.
To remove the clear plastic covers in front of the labels:
1. Carefully insert a small screwdriver into the cut-out at the bottom of the plastic cover.
2. Gently lift the cover, and bend it in the middle. Take care not to force the cover or the
front panel.
To reattach the plastic covers with paper labels:

16 en | Configuration PLENA Mixer amplifier, 4-zone, 240W
2019-03 | V1.1 | Operation manual Bosch Security Systems B.V.
1. Insert the paper label into the holder at the front of the unit.
2. Pick up the cover, and then bend it slightly in the middle by hand.
3. Fit the cover into the slot at the front of the unit, and then gently release the cover,
making sure that the paper label stays in place.

PLENA Mixer amplifier, 4-zone, 240W Operation | en 17
Bosch Security Systems B.V. Operation manual 2019-03 | V1.1 |
7 Operation
7.1 Switching on and off
To switch on unit, set the power button (1) on the front panel to On - pushed in (see Front
panel, page 9).
To switch off the unit, set the power button (1) on the front panel to Off - popped out (see
Front panel, page 9).
7.2 Microphone control
Use the input level control knobs to individually control the sound level of microphone/line
input 1 and microphone inputs 2 and 3.
Notice!
Users can create custom labels for the microphone and microphone/line inputs, description
of the music sources, and audio output zones 1 to 4. These labels can be attached to the
mixer amplifier at position numbers 2, 3, and 5 (see Front panel, page 9).
Colored pins can also be inserted at various positions around the control knobs to indicate
the favorite settings for a particular application.
7.3 Music control
7.3.1 Source selection
Use the music source selector (9) to select one of the connected music sources. The selected
source will be indicated by a green LED.
The music input selected is stored in the unit. Therefore, it is not necessary to repeat the
selection after restart.
7.3.2 Volume control
Use the music source volume control knob (11) to control the sound level of the selected
music source.
7.4 Tone control
The tone control knobs provide separate control of high frequency (treble) and low (bass)
frequency audio for the mixed input of mic/line and music.
The tone controls are not standard bass and treble controls: they can be used as a traditional
tone control with high and low control, but also have a powerful contour that addresses
problems found in real situations.
The tone control boosts warmth in voices and deep bass without boosting rumble, and cuts
rumble without losing warmth or making the sound boomy in the low frequencies. In the high
frequencies, the tone control boosts sparkle without adding sharpness, but when cutting is
first, cuts harshness and sharpness without reducing audio clarity.
Use the Hi (high) and Lo (low) tone control knobs (see Front panel, page 9, numbers 4 and 12)
to change the tone of the mixed output.
7.5 Output control
7.5.1 Zone selection
Use the zone selection buttons (13 to 16) to route the music/microphone, line mix from the
amplifier output to loudspeaker zone 1, 2, 3 and/or 4.

18 en | Operation PLENA Mixer amplifier, 4-zone, 240W
2019-03 | V1.1 | Operation manual Bosch Security Systems B.V.
However, telephone/ 100V emergency announcements are always routed to all zones,
irrespective of the position of the zone selection buttons.
7.5.2 Master volume control
Use the master volume control knob (6) to collectively control the sound level of all outputs,
except the emergency announcement/signal.

PLENA Mixer amplifier, 4-zone, 240W Troubleshooting | en 19
Bosch Security Systems B.V. Operation manual 2019-03 | V1.1 |
8 Troubleshooting
Problem Possible cause Possible solution
Amplifier does not work and
power LED is not illuminated.
– Power (plug) is
disconnected and/or the
unit is switched off.
– Insert power cord and
switch on the unit.
No audio.
– An audio output cable
has come loose or has
not been properly
plugged in.
– Input source is not
working correctly.
– Check all input and
output audio
connections, plug in
audio cables properly.
– Check the input source
is working correctly and
sending an appropriate
level of signal.
The audio output sound is
distorted or sounds strange.
– The audio output cable
has not been properly
plugged in.
– The correct cables have
not been used.
– The input level is
clipping.
– Music source signal level
is not correct.
– Check all connections
are plugged in properly.
– Use correct cable type
for input and output.
– Turn down the input
signal level using the
level control knob or the
master volume control
knob.
– Increase signal level for
the source or change the
source.
8.1 Customer service
If a fault cannot be resolved, please contact your supplier or system integrator, or go directly
to your Bosch representative.

20 en | Maintenance PLENA Mixer amplifier, 4-zone, 240W
2019-03 | V1.1 | Operation manual Bosch Security Systems B.V.
9 Maintenance
The unit requires minimum maintenance. However, to keep it in good condition, the following
tasks should be carried out.
Clean the unit
– Periodically clean the unit with a damp, lint-free cloth.
Clean the air inlets
– The unit can collect dust from operation. Clean the air inlets at least once a year.
Check the connectors and grounding
– Periodically check:
– All cable connections for corrosion and the screw terminals to make sure that they
have not become loosened.
– The ground (Protective Earth) connection of the unit.