CX-A850 Amplifier
Installation & User Guide
V 4.0
Cloud Electronics Limited
140 Staniforth Road, Sheffield, S9 3HF England
Tel +44 (0) 114 244 7051
Fax +44 (0) 114 242 5462
E-Mail: info@cloud.co.uk
Web site: http://www.cloud.co.uk
CX-A850:
Installation and Operation Manual 1
CX-A850 Amplifier
Installation and operation manual
Contents
1 Safety Notes ..............................................................................2
3 Installation..................................................................................2
4 Input Facilities............................................................................2
5 Input Routing Schematics..........................................................3
6 Output Details............................................................................4
7 100V Line operation...................................................................4
8 Bridged Mode Operation............................................................4
9 Status Indicators........................................................................5
10 Power Supply Capacity..............................................................5
11 VCA Modules.............................................................................5
12 VCA Module Installation.............................................................5
Section
2 General Description ...................................................................2
Page
13 Remote Level Plate Connections...............................................6
14 Speaker Equalisation Modules...................................................6
15 Equalisation Module Installation.................................................7
16 Field Servicing ...........................................................................7
17 General Specifications...............................................................7
18 Technical Specifications.............................................................8
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2
1 Safety Notes
Do not expose the unit to water or moisture
•
• Do not expose the unit to naked flames.
Do not block or restrict any air vent
•
• Do not operate the unit in ambient temperatures above 45oC
Do not touch any part or terminal carrying the hazardous live symbol ( )
•
while power is supplied to the unit.
• Do not perform any internal adjustments unless you are qualified to do so and fully
understand the hazards associated with mains operated equipment.
The unit has no user serviceable parts. Refer any servicing to qualified service
•
personnel.
• If the moulded plug is cut off the lead for any reason, the discarded plug is a
potential hazard and should be disposed of in a responsible manner.
For more detailed information refer to the rear of the manual.
2 General
The CX-A850 is an eight-channel power amplifier with a typical output of 50 watts per
channel into a 4Ω load. The unit features extremely low distortion and low noise together
with a high slew rate. Full circuit protection is provided and the load is disconnected if the
heat sink overheats or any DC is detected at the output. A five-second switch-on delay
operates to avoid any switching thumps or other extraneous signals reaching the speaker
system. The CX-A850 also has Dynamic Clipping Protection (DCP) that will automatically
reduce the signal level when the amplifier is driven into clipping thus limiting any clipping
distortion to a low level.
All eight input amplifiers are balanced and have 3-pin plug in screw terminal type input
connectors with adjacent level controls, all mounted on the rear panel. Input signal routing
switches are provided and allow the unit to operate in many configurations whilst retaining
simple input connections.
3 Installation
The CX-A850 is suitable for mounting in a standard 19" equipment rack and occupies two
units of rack space. Sufficient ventilation must be provided for the unit. The amplifier draws
cool air through the front panel and exhausts through the side panels and care must be
taken not to obstruct the airflow otherwise the unit may intermittently turn off due to the builtin thermal protection. The unit is 320mm deep but a depth of 400mm should be allowed to
clear the connectors.
4 Input Facilities
All eight inputs are balanced and use 3-pin plug-in screw terminal type connectors (3.5mm
pitch). All inputs have a level control adjacent to their respective connector. Rear panel
mounted switches provide input routing on channels 2 to 8 allowing a variety of
configurations.
In its default configuration, the unit operates as eight independent amplifiers. Four stereo
pairs, driven from one stereo source and eight channels driven from one mono source are
also possible by suitably configuring the input routing switches. Schematic diagrams of the
switching network in various configurations can be found on page 3.
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Installation and Operation Manual
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CX-A850:
Installation and Operation Manual 3
5 Input Routing Diagrams
8 independent mono amplifiers
Fig 1
8 mono outputs fed from 1 mono
input
4 stereo amplifier pairs fed from 1
stereo input pair
Fig 2
Fig 3
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4
R
Black
W
P
Blue
100V
0V
SPEAKEROUTPUTS
OUTPUTRATING50W/4OHMS
MINLOAD4OHMS
0V
CH1
0V
CH2
0V
CH30VCH4
0V
CH5
0V
CH6
0V
CH7
0V
CH8
6 Output Details
Eight 2-pole plug-in screw terminal type connectors (5mm pitch) are provided on the rear
panel for the eight speaker outputs; these can accommodate flexible leads up to 2.50mm².
Do not make any connections to the unit with the power cable attached. It is good practice to
distance the output wiring from the input wiring and keep the speaker wires twisted until they
7 100V Line operation
are terminated to reduce any cross-talk to a minimum level.
CXL-40T Wired to Channel 8
An optional single-channel externally
mounted 40W 70V/100V-line
transformer module (CXL-40T) is
available for the CX-A850. The
installer can select 70 or 100V
operation by wiring the speaker
network to the 70V or 100V output
terminals on the CXL-40T. When a
CXL-40T is installed to a zone, the
65Hz high pass filter for that zone
must be switched on using the
appropriate jumper/s. The
instructions below detail the procedure you must follow to activate the appropriate filter
1) Turn the power off & remove the mains lead.
2) Remove the top panel from the unit.
3) Turn the relevant 65Hz high pass filter ‘on’ by moving the relevant jumpers to the ‘ON’
position (see list below).
J1 = Channel 1 J5 = Channel 5
J2 = Channel 2 J6 = Channel 6
J3 = Channel 3 J7 = Channel 7
J4 = Channel 4 J8 = Channel 8
Jumpers J1-8 are located from left to right on the PCB, 57mm in from the rear panel.
4) Replace the top panel.
If a filter is not switched on, operation at high input levels and low frequencies may result in
the transformer saturating and the amplifier’s VI and clip limiting operating.
A 2U 19" rack panel (CXL-800) is also available which can accommodate up to 8 CXL-40T
transformer modules.
8 Bridged Mode Operation
The unit can be operated in Bridged Mode using any two channels (see Fig 5). The two
amplifiers that are to be bridged must have the same signal input fed to each of them and be
out of phase with each other. The input level controls of the two channels should both to be
set to the fully clockwise position.
CX-A850:
Installation and Operation Manual
Fig 4
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Fig 5
Wiring Channels 7 and 8 in Bridged Mode
CX-A850:
Installation and Operation Manual 5
The output load should then be connected between the two positive (HOT) outputs of the
relevant channels (no connection to common). You must ensure that the positive wire is
connected to the "first channel" output and the negative wire is connected to the "second
channel" output (see fig 5).
9 Status Indicators
The front panel of the CX-A850 has an array of LED’s that indicate the status of all eight
channels (see Fig 6).
The lower green ‘signal’ LED illuminates when a signal is detected, the yellow 'peak' LED will
illuminate when the amplifier’s DCP is operating and the top red ‘protect’ LED indicates that
the protection relay has disconnected the load. Please note that it is normal for all four red
LED's to illuminate for approximately five seconds when the unit is switched on, indicating
operation of the switch-on delay circuitry. The green ‘power’ LED at the bottom right of the
front panel illuminates when the power is switched on.
10 Power Supply Capacity
The CX-A850 has up to 100mA of available current for use with additional modules.
Exceeding this limit will cause temporary power supply failure. Use the table below to verify
your proposed system does not exceed this limit.
Module Name Current Required
BOSE® EQ cards: M8, M32, MA12, 402, 502A, 802, MB4, MB24,
502B, 502BEX
BOSE® EQ cards: LT3202, LT4402, LT9402, LT9702 17mA
BOSE® EQ card: M16 24mA
VCA-5 9mA
11 VCA Modules
A single channel VCA module ‘VCA-5’ is available as a plug-in option for
each of the eight channels. When a VCA-5 is installed to a channel it
allows the channel to be controlled remotely with the optional RL-1
remote plate.
The circuitry uses the industry standard 'Thats 2150A' VCA providing
very low distortion and up to 90dB attenuation. The VCA module can be
wired to provide muting by using an auxiliary relay connected to a fire
alarm control panel. Contact our technical department for further details.
12 VCA Module Installation
1. Turn the power off and remove the mains cable
2. Remove the top panel
3. Select the required PCB mounted VCA connector and
remove its jumper (see list below & Fig 8)
CON1 = Channel 1 CON5 = Channel 5
CON2 = Channel 2 CON6 = Channel 6
CON3 = Channel 3 CON7 = Channel 7
= Channel 4
CON4
4. Unscrew the relevant blanking plate from the rear of the unit
& retain the screw.
CON8
= Channel 8
Fig 6
12mA
Fig 7
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Fig 8
6
CX-A850:
Installation and Operation Manual
5. Adjacent to the connector there is an M3 fixing screw remove & retain this screw then fit a 35mm
M3 hex spacer (supplied) in its place.
6. Push the 10-way VCA plug onto the PCB connector, aligned so the cable enters it from the rear of
the chassis (See Fig 9) check there is contact with all 10 pins.
7. Position the VCA modules 3-pin socket through the rear panel cut-out and secure using M3 screws
(both removed earlier) VCA Modules Installed to Channel 1&2
8. Replace the top panel.
Side View of VCA Ribbon Cable
Fig 9
13 Remote Level Plate Connections
The RL-1 is a remote control plate that allows the level of a specific channel to be remotely
controlled (in conjunction with the VCA-5). The RL-1 is compatible with UK domestic
electrical accessories and can be mounted onto a standard British flush or surface mounted
25mm deep back box.
Fig 11
As Fig 11 shows, the RL-1 is to be connected to a CX-A850 remote connector with a twocore cable that has an overall screen. It is possible to connect a single remote control
module to control more than one channel simultaneously (Fig 11 right). As more channels
are linked the law of the control will be compromised resulting in an uneven control of
volume; this has proved to be of little consequence operationally.
14 Speaker Equalisation Modules
Each channel of the CX-A850 can have a speaker equalisation module installed so that its
output will be compensated correctly for a wide range of speakers.
Available Equalisation Modules:
- Bose® Speaker models:
LT3202, LT4402, LT9402, LT9702
M8, M16, M32, MA12, 402, 502A, 502B, 502BEX, 802, MB4, MB24,
Fig 10
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CX-A850:
Installation and Operation Manual 7
15 Equalisation Module Installation
1. Turn the power off and remove the mains lead.
2. Remove the top panel from the unit. Channel 7&8 PCB Connector Locations
3. Select the required PCB connector (see
Fig 12 adjacent) that you wish to install
the equalisation module to and remove
the jumper from it.
CON12 & J9 = Channel 1
CON13 & J10 = Channel 2
CON14 & J11 = Channel 3
CON15 & J12 = Channel 4
CON16 & J13 = Channel 5
CON17 & J14 = Channel 6
CON18 & J15
= Channel 7
CON19 & J16 = Channel 8
4. Configure the relevant 65Hz filter to ‘ON’ and connect a CXL-40T 100V line transformer
(see section 7)
5. Fit the EQ card to the connector such that the EQ card is perpendicular to the main board
6. Push down on the EQ card until it locates with a click.
7. Replace the top panel.
NOTE: Before installing active modules, check section 10 for details of the power supply on
the CX-A850. Each channel of the CX-A850 can have both a VCA-5 module and a speaker
EQ card installed at the same time.
16 Field Servicing
The CX-A850 is ruggedly built and uses proven reliable circuitry. It requires no more than the
occasional removal of any dust that may have built up inside the unit because of the forced
cooling.
17 General Specifications
Inputs Balanced via 3-pin plug-in screw terminal type connectors
Outputs 2-pin plug-in screw terminal type connectors for flexible cables up to 2.5mm²
Protection VI limiting, DC offset, Thermal, Switch-on Delay & Dynamic Clipping
Protection
Status Indicators LED indicators on each channel for Signal, Peak &Protect
Cooling Force cooled using variable speed DC fan
Dimensions 482.6mm x 88.0mm (2U) x 300.0mm deep (+ connectors)
Weight 8.8kgs
Fig 12
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CX-A850:
Installation and Operation Manual
18 Technical Specifications
Number of Channels Driven Rated Output 4 Ohm load(s) Rated Output 8 Ohm load(s)
1 62W 36W
2 58W 34W
3 54W 32W
4 50W 30W
5 47W 29W
6 44W 28W
7 41W 27W
8 38W 26W
Bridged Output 100W nominal into 8 Ohm load, minimum load 8 Ohms
Frequency Response +0dB –0.5dB 10Hz to 20kHz, switchable high pass filter –3dB
@65Hz
THD+N 0.007%, typical, @1kHz, 60W into 4 Ohms, one channel driven,
measurement BW 22Hz to 80kHz
VCA Module THD+N <0.03% 1kHz, measurement BW 22Hz to 80kHz
Crosstalk
Typical, between adjacent
channels
Input Sensitivity 0dBu (775mV)
Input Impedance 10k balanced / 5k unbalanced
Noise <96dB rms below rated output, unweighted, measurement BW
Power Input 230V ±5% (115V ±5% available)
Fuse rating 230V – T4A H 115V – T8A H
Fuse type 20mm x 5mm class 3T 250V
This product conforms to the following European EMC Standards:
BS EN 55103-1:1997
BS EN 55103-2:1997
This product has been tested for use in commercial and light industrial environments. If the equipment
is used in controlled EMC environments, the urban outdoors, heavy industrial environments or close to
railways, transmitters, overhead power lines etc. the performance of the unit may be degraded.
The product conforms to the following European electrical safety standard.
BS EN 60065:1998
-85dB (relative to 60W) @1kHz with 4 Ohm load
-82dB (relative to 60W) @10kHz with 4 Ohm load
-90dB (relative to 30W) @1kHz with 8 Ohm load
-90dB (relative to 30W) @10kHz with 8 Ohm load
22Hz to 22kHz
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CX-A850:
Installation and Operation Manual 9
Safety Considerations and Information
The unit must be earthed. Ensure that the mains power supply provides an effective earth
connection using a three-wire termination.
When the mains switch is in the off ‘O’ position the live and neutral conductors of the mains
transformer are disconnected, however some parts of the product will still remain connected to
the live and neutral mains conductors
CAUTION – Installation
Do not expose the unit to water or moisture
Do not expose the unit to naked flames.
Do not place liquid filled containers on or around the unit
Do not block or restrict any air vent
Do not operate the unit in ambient temperatures above 45oC
CAUTION – Hazardous Live
Do not touch any part or terminal carrying the hazardous live symbol ( ) while power is
supplied to the unit.
Terminals to which the hazardous live symbol refers require installation by a qualified person.
CAUTION - Mains Fuse
Replace the mains fuse only with the same type and rating as marked on the rear panel. The
fuse body size is 20mm x 5mm.
CAUTION – Servicing
The unit contains no user serviceable parts. Refer servicing to qualified service personnel. Do
not perform servicing unless you are qualified to do so.
Disconnect the power cable from the unit before removing the top panel and do not make any
internal adjustments with the unit switched on.
Only reassemble the unit using bolts/screws identical to the original parts
Bose is a registered trademark of The Bose Corporation
In the interest of continuing improvements Cloud Electronics Limited reserves the right to alter
specifications without prior notice.
Cloud Electronics Limited 140 Staniforth Road Sheffield S9 3HF England
Telephone +44 (0) 114 244 7051 Fax +44 (0) 114 242 5462 E-mail: Info@cloud.co.uk
08-03-05 V4
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