Cloud VTX 4240 User manual

VTX SERIES
POWER AMPLIFIERS
VTX 4120,VTX 4240,VTX 4400
PEAK
SIGNAL
POWER
1 2 3 4
PROTECT
CHANNEL
VTX 4120
4x 120W Amplifier
PEAK
SIGNAL
POWER
1 2 3 4
PROTECT
CHANNEL
VTX 4240
4x 240W Amplifier
PEAK
SIGNAL
POWER
1 2 3 4
PROTECT
CHANNEL
VTX 4400
4x 400W Amplifier
O
I
O
I
O
I
Installation and User Guide

VTX Series User Manual v1.03
Safety Information ........................................ 4
Safety Notes regarding Installation........................4
Safety Considerations and Information ................4
General Description...................................... 5
VTX range main features .........................................5
Applicable Models......................................................5
Block Diagram............................................... 5
Front Panel Description ............................... 6
Rear Panel Description................................. 6
Installation ..................................................... 7
Mechanical ...................................................................7
Ventilation....................................................................7
Connections and adjustments.................................7
Protection ...................................................... 9
Bose® equalisation modules
(optional)...................................................... 10
Installation .................................................................10
General Notes ............................................. 10
EMC Considerations...............................................10
Earthing ......................................................................10
Appendix...................................................... 11
Technical Specications ..........................................11
General Specications ............................................11
Location of jumpers and other internal
components ..............................................................12
Factory default jumper settings table..................13
Contents

VTX Series User Manual v1.04
Safety Information
Safety Notes regarding Installation
•Do not expose the unit to water or moisture.
•Do not expose the unit to naked ames.
•Do not block or restrict any air vent.
•Do not operate the unit in ambient temperatures above
35OC.
•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 qualied to do so and fully understand the hazards
associated with mains-operated equipment.
•The unit has no user-serviceable parts. Refer servicing
to qualied service personnel.
•If the moulded plug is cut off the AC power lead for
any reason, the discarded plug is a potential hazard and
should be disposed of in a responsible manner.
Conformities
This product conforms to the following European EMC
Standards:
BS EN 55103-1:2009
BS EN 55103-2:2009
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 60065:2002
The VTX Series was developed and manufactured with high
quality materials and components, which can be recycled
and/or reused.
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.
Caution - High Voltages
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 qualied person.
Caution - Mains Breaker
VTX Series ampliers are tted with a resettable mains
circuit breaker instead of a replaceable fuse.This is located
on the rear panel above the AC mains input connector.The
circuit breaker may be reset by pressing it in; however, its
operation may indicate an internal fault. If the circuit breaker
operates immediately the power is restored, no further
attempt should be made to use the amplier, and it should
be returned to your Cloud service centre or other qualied
person for repair.
Caution - Servicing
The unit contains no user serviceable parts. Refer servicing
to qualied service personnel. Do not perform servicing
unless you are qualied 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.
What’s in the Box
Please check the shipping carton for damage; if there is any,
please contact your Cloud agent and the shippers.
The packing carton should contain the following items:
• VTX amplier
• IEC mains lead
• Set of mating screw-terminal connectors
• Set of four push-in feet (for free-standing use)
• This manual

VTX Series User Manual v1.0 5
General Description
Cloud VTX ampliers are a range of high power multi-
channel audio ampliers intended for use with high quality
PA and music systems in locations where unquestionable
long-term reliability is the primary consideration.As well as
theatres, leisure centres and other major venues, they are
also ideal for airport terminals, railways stations and similar
large public spaces.
VTX ampliers deliver excellent audio quality at all rated
powers and have all the facilities and features that installers
have come to expect from Cloud products.The VTX range
are the rst Cloud products to offer a plug-in surveillance
card option, permitting the operating parameters and
settings of all networked ampliers to be monitored
anywhere, using any computer’s standard web browser.
Applicable Models:
This manual describes the installation and operation of the
following models:
• Cloud VTX4120 4-channel amplier
– 4 x 120 W into 4 ohms
• Cloud VTX4240 4-channel amplier
– 4 x 240 W into 4 ohms
• Cloud VTX4400 4-channel amplier
– 4 x 400 W into 4 ohms
All models are 2U, 19” rack-mounting units.Apart from
the output power rating, the three models are identical for
the practical purposes of installation and operation. Unless
specically stated otherwise, the information in this manual
may be taken to apply to all models.
VTX range main features:
• High power multichannel ampliers for “install-and-
forget” applications
• 120 W, 240 W or 400 W per channel into 4 ohms
(model-dependent)
• Extensive protection against short-circuit and reactive
loads, clipping, DC and overheating
• Chs1 & 2 and/or 3 & 4 may be operated in Bridge Mode
• Per-channel, front-panel LEDs for power status, signal
presence, peak level and protection
• Balanced line level inputs with gain trim
• Congurable for 4 channel, dual stereo or mono use
• Per-channel switched hi-pass lter
(18 dB/oct below 65 Hz)
• Optional VTX-WM1 card allows amplier monitoring
from a standard web browser
• Optional remote volume control (per-channel)
• Optional Bose® EQ cards (per-channel)
• 2U 19” rackmounting unit
• Forced-air cooling
• Five year warranty
Block Diagram
g.1: VTX Series Block Diagram

VTX Series User Manual v1.06
Front Panel Description
1POWER LEDs - (one per channel) – illuminate after
power-up sequence to conrm normal power supply
operation
2SIGNAL LEDs – (one per channel) – illuminate when
the input signal level exceeds -26dBu
3PEAK LEDs – (one per channel) - illuminate if
amplier clipping is detected
4PROTECT LEDs – (one per channel) – illuminate if
the internal heatsink temperature exceeds 90 °C
5AC Power switch
6Air intake grilles
Rear Panel Description
1Input connectors (one per channel)
2Input level controls (one per channel)
3High Pass Filter controls (one per channel)
4Input routing switches
5Bridged mode switches
6Remote volume control connectors (one per
channel)
7Output connector
8Bay for optional WM-1 surveillance card*
(cover plate tted when no card present)
9AC mains connector
10 Resettable mains circuit breaker
11 Earth safety tag
12 Air exhaust grilles
125
436 6
g.2: VTX Front Panel (NOTE:VTX4120 shown – other models are identical)
CHANNE
L
2
C
HANNE
L
1 CHANNE
L
3
C
HANNE
L
4
C
H
3
C
H
4
C
H
2
S
PEAKER
O
UTPUT
S
0
V
C
H
1
0
V
C
H2
0
V
C
H3
0
V
C
H4
ON
O
F
F
ON
O
F
F
O
N
O
F
F
B
RID
GE
1
-
2
ON
O
F
F
BRID
G
E
3
-4
4
O
HM
S
- MIN
BRIDG
E
3-4
B
RID
GE
1
-
2
P
O
WER ~ 40-60H
z
1
0%
1
4 4 4
72
36
8
10111212
5 5
9
g.3: VTX Rear Panel (NOTE: rear panel is identical for all models)
*The optional WM-1 surveillance card allows remote monitoring of the amplier’s performance and settings from any computer via
a standard web browser. Full instructions regarding the installation, conguration and use of the WM-1 are contained in the WM-1
Installation and User Guide, supplied separately with the card.

VTX Series User Manual v1.0 7
Installation
Mechanical
VTX ampliers are designed to be mounted in a standard
19” equipment rack. The front panel is tted with rackmount
ears for this purpose. Each amplier requires 2U of
vertical rack space. See notes below regarding spacing and
ventilation.
Due to the units’ weight, the use of additional rear supports
is strongly recommended.
Ventilation
VTX ampliers are force cooled by two thermostatically-
controlled fans mounted internally on the main PCB.The
fans are always operational, and run at a higher speed when
required.
Always allow adequate space around the amplier(s) to
allow a free ow of air through the unit(s). Ensure that cable
bundles or other items do not obstruct any grilles.
In 19” rack applications we recommend leaving 1U of rack
space above and below each unit. Plain 1U blank panels,
not slotted ventilation panels should be used, as the latter
reduce the effect of forced-air cooling.The direction of
airow in VTX ampliers is front-to-rear; it is recommended
not to mix these ampliers with other equipment employing
forced-air cooling which acts in the opposite direction
within the same rack.
If using the amplier free standing, we recommend tting the
feet supplied and placing the unit on a at surface, leaving the
ventilation grilles free from any obstructions.
Connections and adjustments
Inputs
Each amplier channel has an electronically-balanced input on
a 3-pin, 3.5 mm-pitch screw terminal connector.The mating
connector is supplied.Twin-core screened cable should be
used when driving the amplier inputs from a device with a
balanced output. Single-core screened cable can be used when
connecting to an unbalanced source.Wire the inputs to the
source devices using the convention shown below:
Sensitivity and Gain Control
Control of input level is provided by a preset rotary
control adjacent to each input connector.The control
should be adjusted using a trimtool or small screwdriver.
Full attenuation of the input signal – i.e., zero output – is
obtained with the control fully anti-clockwise. Maximum
sensitivity is with the control fully clockwise; at this setting
the maximum output level will be produced for an input
signal level of 0.775 Vrms (0 dBu).
We recommend that the level for each channel should be
adjusted after installation is complete to ensure adequate,
but not excessive sound levels are achieved with the
programme material that will be used in practice.
Input Routing
To facilitate the use of the ampliers in a variety of different
multi-channel applications, input selection switches are
provided on all channels except Ch1.This gives the installer
an easy method of paralleling channels from a single input.
Refer also to g.1 on page 5.
The options are summarised in the table below:
SOURCE FOR Chs. 2-4
Button position: OUT IN
Channel 2 In 1 In 2
Channel 3 In 1 In 3
Channel 4 In 2* In 4
*post Ch 2 switch
g.4: Input Wiring





























VTX Series User Manual v1.08
The three switches on the rear of VTX ampliers allow a total of 8 routing possibilities, including 4-channel, dual stereo and
mono operation with 4 channels paralleled. The table below claries the options:
AMPLIFIER
CONFIGURATION
BUTTON POSITION INPUT ROUTING:
AMPLIFIER CHANNELS FED BY EACH INPUT
CH 2 CH 3 CH 4 IN 1 IN 2 IN 3 IN 4
4-channel IN IN IN CH 1 CH 2 CH 3 CH 4
Dual mono + stereo OUT IN IN CHS 1 & 2 CH 3 CH 4
Dual mono + stereo IN OUT IN CHS 1 & 3 CH 2 CH 4
Treble mono + 1 OUT OUT IN CHS 1, 2 & 3 CH 4
Dual mono + stereo IN IN OUT CH 1 CHS 2 & 4 CH 3
Treble mono + 1 OUT IN OUT CHS 1, 2 & 4 CH 3
Dual stereo IN OUT OUT CHS 1 & 3 CHS 2 & 4
Quad mono OUT OUT OUT CHS 1, 2, 3 & 4
Remote Control of Level
VTX ampliers are compatible with standard Cloud remote
control plates Type RL-1, allowing control of level from a
remote position. RL-1s may be connected at the rear 3-pin,
5 mm-pitch screw terminal connectors (REMOTE LEVEL),
using the wiring shown below.
Use two-core screened cable to connect the remote level
plate (maximum length 100 metres).
High Pass Filters
Each channel of the VTX is tted with a switchable hi-pass
lter, which may be switched in as required to reject low-
frequency signals below 65 Hz. The lter has a slope of
18 dB/octave, to provide a high degree of low frequency
rejection.
The primary purpose of the lter is to avoid loudspeaker
transformer saturation when driving 100V/70 V-line speaker
systems. (The VTX ampliers’ outputs are designed to drive
low-impedances only, so an external transformer will be
necessary for amplier channels to drive such systems. The
Cloud CXL-100T is suitable for use with theVTX4120;
transformers with higher ratings will be necessary for use
with the VTX4240 and VTX4400).Transformer saturation
creates unpleasant distortion and stresses the system, and
the high pass lter should always be switched in when
driving 100 V/70 V-line systems.
Use of the lter with low-impedance loudspeaker systems
is optional and at the discretion of the installer; switching
it in may help to enhance the clarity of speech, reduce
microphone handling noise and breath blasts.
Outputs
The VTX ampliers’ speaker output connections are on
two adjacent 4-pin, 5 mm-pitch screw-terminal connectors
(mating connectors are supplied).
CH 1CH 2CH 1CH 3CH 4
-+-+-+-+
Each channel’s output stage is designed to drive into an
impedance of not less than 4 ohms. Check the impedance of
the loudspeaker(s) in use and, taking into account any series
and/or parallel wiring, ensure that the total load on each
channel is not less than 4 ohms.
g.6: Output Wiring
g.5: RL-1 Wiring
123
REMOTE MUSIC
CONTROL
CONNECTOR
123
RL-1
USE TWO-CORE SCREENED CABLE

VTX Series User Manual v1.0 9
100 V/70 V-line operation
VTX ampliers may be used to drive 100 V-line or 70 V-line
speaker systems with the addition of appropriate external
transformers.The Cloud CXL-100T is suitable for use with
the Model VTX4120, and one transformer will be required
per channel.A 2U rack-mounting tray (CXL-800) is also
available to facilitate the installation of up to eight
CXL-100Ts. Models VTX4240 and VTX4400 require
transformers with a higher rating.
Bridged Mode
VTX ampliers may be operated in Bridged Mode to achieve
higher power outputs. Channels 2 and 4 are tted with rear
panel mode switches; Channels 1 and 2 may be operated as
a bridged pair by setting the BRIDGE 1-2 switch on Channel
2 on; similarly Channels 3 and 4 may be bridged with
Channel 4’s BRIDGE 3-4 switch.
The principle of Bridged Mode is to feed the same input
signal to two amplier channels, but with one input phase-
inverted. The “high” output terminals of the two channels
will therefore assume the same instantaneous voltage, but
of opposite polarity. In Bridged Mode, the load is connected
across the two “high” terminals, thus doubling the effective
voltage swing.
PHASE
INVERT
Ch. A
Ch. B
0 V
V
V
2V
0 V
+
+
When using pairs of channels in Bridged Mode, wire the
outputs in accordance with the diagram below:
CH 1CH 2CH 1CH 3CH 4
-+-+-+-+
Note that no connection is made to the ‘0V’ terminal of
either channel in the bridged pair. Note also that Channels
1 and 2 may be operated in Bridged Mode while 3 and 4 are
in Normal Mode – and vice versa.
Protection
The ampliers include comprehensive protection circuitry
to prevent damage to loudspeakers, the output devices and
other components in the event of a fault condition.
Thermal Protection
The output device heatsink temperatures are monitored and
the protection circuitry activated if any should exceed 90°C.
The red front panel PROTECT LED for the appropriate
channel illuminates to indicate the fault condition.
DC Protection
Crowbar protection is provided to safeguard the
loudspeakers in the event of DC being present at the output
terminals.This is an emergency protection system, and
its operation is liable to blow internal DC rail fuses.The
amplier must be serviced before any attempt is made to
use it further.
Short-circuit/reactive load protection
VI limiting is implemented in the ampliers to protect
the output stage from excessive voltage or current at the
output.This condition can arise from a short-circuit (or
near-short-circuit) across the output terminals, or from an
excessively inductive or capacitive load.
Switch-on protection
The protection circuitry is also activated immediately
after the amplier is switched on. This is to prevent any
voltage spikes due to start-up conditions from damaging
the loudspeakers.The duration of the protection period is
approx. two seconds. When the amplier is powered on,
all PROTECT LEDs ash briey; the POWER LEDs do not
illuminate until after the protection period (assuming no
amplier faults exist).
g.7: Bridged Mode Principle
g.8: Output Wiring - Bridged Mode

VTX Series User Manual v1.010
Bose® equalisation modules
(optional)
VTX ampliers are compatible with Bose® Series II
loudspeakers; a single-channel Bose® equalisation module
may be tted to as many channels as necessary. Equalisation
modules for the following Bose® models are available:
• Panaray MA12
• Panaray 402-II, 502B and 502BEX
• Panaray LT Series: Models 3302, 4402, 9402 and 9702
Other modules are available to provide the correct
equalisation for loudspeakers from other manufacturers as
well as for other Bose® models; please contact Cloud for
more details.
Installation
• With the power turned off and the mains cable
removed, remove the top panel.
• Refer to the PCB layout diagrams at g.9 on page 12.
The modules plug into the white 12-pin connectors
(J104 to J404) on the upper PCB adjacent to the rear
panel. Note the header connectors on the PCB have
two notches on one side only; these engage with lugs on
the equalisation module’s mating connector to ensure
correct orientation.
• After tting equalisation modules to any channel(s), the
corresponding module bypass jumper(s) (J108 to J408)
must be removed in order for the module to function.
Refer to the PCB layout diagrams for full details.
• Replace the top cover with the original screws after
tting.
General Notes
EMC Considerations
Cloud VTX ampliers fully conform to the relevant
electromagnetic compatibility (EMC) standards and are
technically well behaved.You should experience no problems
interfacing units to other items of equipment and under
normal circumstances, no special precautions need to
be taken. If the unit is to be used in close proximity to
potential sources of HF disturbance such as high power
communication transmitters, radar stations and the like,
it is suggested that input signal leads be kept as short as
possible.Always use balanced interconnections wherever
possible.
Earthing
When several mains powered units are connected together
via their signal cables, there is a risk of one or more earth
loops which may cause an audible hum on the system even
with the gain controls set to minimum.The 0 V rail of a
VTX amplier is directly coupled to the chassis ground. No
interconnection problems should be encountered, but if
there is any hum or other extraneous noise when source
equipment is connected, the situation can generally be
remedied by observing the following guidelines:
• Always connect sources using balanced connections
wherever possible, with the cable screen only connected
at the receiving end (amplier input).
• Use audio isolating transformers (readily available from
trade suppliers) at the inputs if necessary.These will
ensure that the amplier is electrically isolated from the
source equipment.
The signal source units should be located as close as
possible to the ampliers and the metal housing of the
various units should not be electrically connected together
through the equipment rack. If this is a problem, rack
isolating kits are available from specialist hardware suppliers.
If the problem persists, try to connect all interconnected
units, including power ampliers, to a common power source
to ensure a common ground is provided.

VTX Series User Manual v1.0 11
Appendix
Technical Specications
VTX4120 VTX4240 VTX4400
Output (Normal Mode) 120 W (4Ω) 240 W (4Ω) 400 W (4Ω)
Output (Bridged Mode) 240 W (8Ω) 480 W (8Ω) 800 W (8Ω)
Frequency Response 20 kHz to 20 kHz, +0/-1 dB; (HPF bypassed)
High Pass Filter -3 dB @ 65 Hz, slope 18 dB/octave (switchable)
Distortion THD + N <0.03% @ 1 kHz, 1 W output, 4 Ω load
Crosstalk < -90 dB @ 1 kHz, -70 dB @ 10 kHz
Sensitivity 0.775 Vrms (0 dBu)
Input Impedance 10 kΩ, balanced
Noise (rms) <100 dB below full output power, 20 Hz to 20 kHz
General Specications
VTX4120 VTX4240 VTX4400
Inputs Electronically balanced; 3-pin 3.5 mm-pitch plug-in screw terminal connectors
Outputs 2-pin 5 mm-pitch plug-in screw terminal connectors
Main Protection By resettable rear-panel circuit breaker
Amplier Protection Clip Limiting,VI Limiting, DC Offset,Thermal & switch-on delay
Status Indicators LED Indicators on each channel for Power Status, Signal Presence, Peak Level & Protection
Cooling Two mid-mounted variable speed DC fans
Dimensions
(mm,W x H x D)
482.6 mm x 88.3 mm (2U) x 416 mm (exc. connectors); 450 mm (inc. connectors)
Weight 13.8 kg (net) 16.5 kg (net) 20.0 kg (net)

VTX Series User Manual v1.012
Location of jumpers and other internal components
g.9: Jumper Locations
NOTE:
The following jumpers and connectors are relevant to the
optional VTX-WM1 surveillance card:
J109 - J409
J110 - J410
J107 - 407A
J801B, J802B
Full details are in theVTX-WM1 Installation and User Manual
BOSE® EQ
Card Sockets
BOSE® EQ
Card Bypass Jumpers

VTX Series User Manual v1.0 13
Factory default jumper settings table
Jumper/Connector Function Channel No. Default Setting
J104
Bose® EQ card sockets
1
Empty
J204 2
J304 3
J404 4
J108
Bose® EQ card bypass jumpers
1
Present
J208 2
J308 3
J408 4
J107A
VTX-WM1 surveillance card interface sockets
1
Empty
J207A 2
J307A 3
J407A 4
J801B All
J802B All
J805B* 1&2
J806B* 3&4
J109
VTX-WM-1 card bypass jumpers
1
Present
J209 2
J309 3
J409 4
J110 1
J210 2
J310 3
J410 4
*These connectors are on the lower (main) pcb.

VTX Series User Manual v1.014
Bose® is a registered trademark of The Bose Corporation.
In the interest of continuing improvements Cloud Electronics Limited reserves
the right to alter specications without prior notice.

Cloud Electronics Limited
140 Staniforth Road
Shefeld S9 3HF
England
Tel: [phone]
Fax: [phone]
email: [email protected].uk
web: www.cloud.co.uk