Full Text Searchable PDF User Manual
CX-A4 Amplifier
Installation & User Guide
V9.0
Cloud Electronics Limited
140 Staniforth Road, Sheffield, S9 3HF England
Tel + 44 (0) 114 244 7051
Fax + 44 (0) 114 242 5462
Web site http://www.cloud.co.uk
CX-A4
I
NSTALLATION AND OPERATION MANUAL
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CX-A4 Amplifier
Installation and operation manual
Contents
Section
Page
1
General
Description ...................................................................2
2 Installation ..................................................................................2
3
Input
Facilities ............................................................................2
4
Output
Details ............................................................................4
5
100V
Line
operation ...................................................................4
6
Configuring the CX-A4 for 100V Line operation .........................5
7
Bridged
Mode
Operation ............................................................5
8
Status
Indicators ........................................................................5
9
VCA
Modules .............................................................................6
10
Peak
Limit
+ VCA Modules ........................................................6
11
Remote
Level Connections ........................................................6
12
Bose
Equalisation Modules ......................................................7
13
Installing
Optional Modules ........................................................7
14
Field
Servicing............................................................................8
15
General
Specifications ...............................................................9
16
Technical
Specifications .............................................................9
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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 35
o
C
•
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-A4 is a four-channel power amplifier with a maximum channel output of 120 watts
into 4 ohms. 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.
All four input amplifiers are balanced and connect via 3 pin XLR type 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.
The CX-A4 amplifier can be used with up to two optional plug-in two channel VCA
modules to provide remote level control. Each plug-in module can operate as two
individual attenuators or can be linked to operate as a stereo pair with one remote level
control.
3 Installation
The CX-A4 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 right side and care must
be taken not to obstruct the airflow otherwise the unit may intermittently turn off due to the
built-in thermal protection. Applications, which require long, sustained operation at high
power levels, should allow a 1U space above and below the unit. The unit is 325mm deep
but a depth of 400mm should be allowed to clear the connectors.
4 Input
Facilities
All four inputs are balanced and use 3 pin XLR type connectors. All inputs are wired to
the standard convention of pin 1 ground, pin 2 in-phase, pin 3 reverse phase, with the
shell of the connector connected to the chassis. If the unit is operating in a location which
has a high level of electrical or magnetic disturbance or is close to a TV or radio
transmitter, we suggest that the input cable screen be connected to the shell of a metal
XLR type connector. If the signal is from an unbalanced source, connect pin 3 to pin 1
(ground) inside the XLR type connector and use pin 2 as hot.
Every input has a level control adjacent to the respective XLR type connector. Input
switching is provided on input channels 2 to 5 allowing a wide variety of input routing
configurations. See the schematic diagrams showing details of various routing
possibilities.
With all input switches depressed, the unit operates as four independent amplifiers.
Three stereo pairs, driven from one stereo source and four channels driven from one
mono source are also possible together with a combination of the two by suitably
configuring the input routing switches.
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1
2
1
3
2
4
INPUT 1
1
2
3
4
POWER
AMPLIFIER
LEVEL
CONTROL
SOURCE
SWITCHES
INPUT
AMPLFIER
FROM MONO SOURCE
FOUR CHANNELS DRIVEN FROM ONE MONO SOURCE
1
2
3
4
1
2
1
3
2
4
INPUT 1
1
2
3
4
POWER
AMPLIFIER
LEVEL
CONTROL
SOURCE
SWITCHES
INPUT
AMPLFIER
FROM STEREO SOURCE
TWO STEREO PAIRS FROM ONE STEREO SOURCE
INPUT 2
1
2
3
4
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1
2
1
3
2
4
INPUT 1
1
2
3
4
POWER
AMPLIFIER
LEVEL
CONTROL
SOURCE
SWITCHES
INPUT
AMPLFIER
INPUT 2
INPUT 3
INPUT 4
FOUR CHANNELS OPERATING AS INDEPENDENT AMPLIFIERS
1
2
3
4
5 Output
Details
Binding posts are provided on the rear panel for the four speaker outputs and these can
accommodate flexible leads up to 2.50mm². The posts are not compatible with 4mm
'Banana' plugs. Each speaker lead should be a twisted pair; having an untwisted section
of cable for as little as 10cm before its termination will significantly increase cross-talk. It
is also good practice to distance the output wiring from the input wiring. Do not make any
connections to the unit with the power cable attached.
6
100V Line operation
Connecting a CXL-100
10
0W 100V-line
module across an output of the CX-A4 will
obtain a
10
0W 100V-line output from that
channel. The CXL-100 has to be mounted
externally of the amplifier and 70V or
100V-line operation is selectable by taking
the output of the CXL-100 from the
necessary 70V or 100V screw terminal.
A 2U 19" rack panel (CXL-600) is available
that accommodates up to six CXL-100
transformer modules.
The following page contains important
information on configuring the CX-A4s
65Hz filters
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7
Configuring the CX-A4 for 100V-line Operation
When a CXL-100 is connected to a channel of the CX-A4, that channel must have its
65Hz high-pass filter operational. Without this filter operational, the presence of high
input levels at frequencies below 50Hz may result in transformer saturation causing the
amplifiers VI limiter to operate. The filter can be switched on by moving the relevant
jumper to the ‘IN‘ position.
Jumpers J1-4 are associated with the channels of the CX-A4 as follows:
J1
= Zone 1
J2
= Zone 2
J3
= Zone 3
J4
= Zone 4
Diagram to Show Location of J1-4 on the CX-A4 PCB
8
Bridged Mono Operation
The unit can operate in Bridged Mode using any two channels. The inputs must be wired
together by linking the input signal at the XLR connectors of the two relevant channels,
wiring the "second" input out of phase (i.e. pin 1 ground, pin 3 in-phase, pin 2 reverse
phase). The input level controls of the two channels should both to be set to the fully
clockwise position.
The output load should then be connected between the two red binding posts of the
relevant channels (no connection to the black binding posts of the relevant channels).
You must ensure that the positive wire is connected to the "first" red binding post and the
negative wire is connected to the "second" binding post.
Thus for example it is possible to configure four channels as two bridged outputs allowing
a stereo input to be delivered to two 240 watt 8 ohm outputs.
9 Status
Indicators
The front panel of the CX-A4 has an array of LED’s that indicate the status of all four
channels. The lower green LED illuminates when a signal exceeding 500mW is detected,
the yellow 'peak' LED will illuminate when the amplifier output is close to clipping and the
top red 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 lower
green LED indicates that the power is switched on.
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10 VCA
Modules
A two-channel VCA module is available as a plug-in option for the CX-A4 (see section 13
for installation details) and is supplied with either one or two control plates. The unit can
operate two channels independently or switched to provide stereo attenuation via one
control plate. For independent operation, the switch should be in the 'solo' position (in),
with the remote level controls connected to both 3 pin connectors. For stereo operation,
position the switch in the link position (out) and connect the level control to the left
connector only. The RL-1 remote control plate is compatible with domestic electrical
accessories and can be mounted onto a standard British flush or surface mounted 25mm
deep back box. Two-core cable with overall screen should be used to connect the remote
level control to the module mounted inside the CX-A4. 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.
Note:
A VCA module cannot be installed to channels that already have a Bose
equalisation module installed.
11 Peak Limit + VCA Modules
A two channel peak limit + VCA module is available (see section 13 for installation
details) which performs the same functions as the module described above with the
added benefit of a peak limiter which is factory set to prevent clipping. A 'Peak Limit'
on/off switch is mounted on the rear panel that can be over-ridden by configuring a PCB
mounted circuit jumper. The limiter operates with hard knee characteristics and has an
infinite compression ratio.
Note:
A Peak Limit + VCA module cannot be installed to channels that already have a
Bose
equalisation module installed.
12 Remote Level Plate Connections
REAR VIEW OF CX-A4 AMPLIFIER
1 2 3
USE 2 CORE SCREENED CABLE
CONNECT SCREEN TO TERMINAL 1
REAR VIEW OF LEVEL CONTROL PLATE
LINK
REMOTE LEVEL
CLIP
PROTECT
OFF
ON
SOLO
1
2
1+2
1
2
SOURCE
1
2
3
1
2
3
1
2
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13 Bose
Equalisation Modules
Each channel on the CX-A4 can have Bose
equalisation so
that its output will be compensated correctly for a wide range
of Bose
speakers. The Bose
equalisation module for the
CX-A4 is a two channel device the CX-A4 requires three
modules to be installed to allow compensation on every
channel of the amplifier.
The Bose
equalisation module is available in two
configurations:
Model 8
- Suitable for B ose
Model 8 Speakers
Model 32
- Suitable for the Bose
Model 25, 32 and 102
speakers
Notes:
•
A Bose
equalisation module cannot be installed to channels with a VCA module
installed.
•
A Bose
equalisation module consisting of a model 8 channel and a Model 32 channel
can be manufactured upon request. Contact our technical department for more details.
14
Installing Optional Modules
There are three optional modules for the CX-A4; the VCA-2, VCAL-1 & the Bose
equalisation module. Components supplied with the various modules are listed below:
VCA-2:
Two 40mm M3 hex spacers, one plastic insert & two 3-pin screw terminal plugs.
VCAL-1:
Two 40mm M3 hex spacers & two 3-pin screw terminal plugs.
Bose
EQ:
Two 25mm M3 hex spacers.
The CX-A4 connectors to install the VCA modules are to the rear of the amplifier on the
input PCB clearly marked on the PCB as ‘CON X TO VCA MODULE’ where ‘X’ is 1 or 2
see below: -
CON
1
= Channel 1&2
CON 2
= Channel 3&4
When installing modules, follow the instructions below carefully. Incorrect installation can
cause damage.
1. Turn the power off and remove mains cable.
2. Remove the top panel.
3. Select the CX-A4 connector you wish to install the module to (see notes above) and
remove the jumpers from it.
4. When installing a VCAL-1 or VCA-2, remove the relevant rear panel blanking plate.
5. When installing a VCA-2, push the plastic plug into the rear panel ‘clip protect’ hole.
6. Two M3 fixing screws can be found adjacent to the CX-A4 connector. Remove and
retain these two screws then fix the M3 hex spacers in their place.
7. When installing a Bose
equalisation module, configure the relevant 65Hz filter to ‘IN’
and connect a CXL-100 100V line transformer (see section 6)
8. Push the 10-way plug onto the CX-A4 connector with the plug aligned so the cable
approaches it from the rear of the chassis and check that the connector mates with all
10 pins (important orientation diagrams can be seen on the following page).
9. When installing a VCAL-1 or VCA-2,
position the 3-pin sockets and switch(es) of the
VCA through the cut-outs in the rear panel.
10. Align the two holes in the module over the top of the two spacers.
11. Secure the module with the two M3x6 screws (removed earlier).
12. Fit the top panel.
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Top Down View of Bose
Equalisation Module Orientation
Bose
Equalisation Module Orientation (Side View) VCA Module Orientation (Side View)
15 Field
Servicing
The CX-A4 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 as a result of the
forced cooling. In the unlikely event of failure, the power amplifier module (2 channels)
can be replaced without special tools and is available as a tested replacement complete
with heat sink. Proceed as follows to replace the power module:
Disconnect all the leads and connectors from the rear of the unit.
Ensure that the mains supply lead has been disconnected.
Remove the CX-A4 from the equipment rack.
Remove the top panel.
The power amplifier modules are arranged as three dual channel units.
Locate the faulty unit and remove both the 7 way power cable & the 10 way ribbon
connector.
Remove the four fixing screws from the bottom of the unit to release the module.
Now fit the replacement unit by proceeding in reverse order.
No setting up is required and the unit should operate normally.
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16 General
Specifications
Inputs
Balanced via 3 pin XLR type connector.
Outputs
Binding Posts for flexible cables up to 2.5mm²
Protection
VI limiting, DC offset, Thermal and Switch-on Delay
Status
LED indicators on each channel for Signal, Peak & Protect.
Cooling
Force cooled using two speed DC fan.
Dimensions
482.6mm x 88.0mm (2U) x 325.0mm deep (+ connectors)
Weight 9kg
net
17 Technical
Specifications
Rated Output
120-watts/4 ohm load 85-watts/8 ohm load.
Bridged Output
240 watts/8 ohm load
Frequency Response
±1dB 10Hz to 50kHz
THD
<0.005% 1kHz <0.05% 20Hz/20kHz 8
Ω
1dB below rated output
VCA Module THD
<0.03% 20Hz/20kHz
Input Sensitivity
0dBu (775mV)
Input Impedance
10k
Ω
balanced / 5k
Ω
unbalanced
Noise
>90dB below rated output.
Slew Rate
35V/µS (power amplifier)
Power Input
230V ±5% (115V ±5% available)
Fuse rating
230V - T4A H
115V - T8A H
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
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
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CAUTION - Installation
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 35
o
C
CAUTION - Hazardous Live
Do not touch any part or terminal carrying the hazardous live symbol ( )
while power is supplied to the unit as it can result in electric shock.
Terminals to which the hazardous live symbol refers require installation by qualified personnel
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 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