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Cloud CX335 Installation And Operation Manual

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CX335 

Installation and Operation 

Manual 

V3.0

 

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

 

 


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CX335

: Installation and Operation Manual 

Page 1 

CX335 STEREO COMPRESSOR LIMITER 

Installation and Operation Manual

 

 

 

CONTENTS 

 
 

Section

  

Page

 

 

Safety Notes

.....................................................................................3 

 

2

 

‘Quick Start’

......................................................................................3 

 2a 

Soft Knee, Normal Envelope

..........................................................3 

 2b 

Hard Knee, Normal Envelope

........................................................4 

 2c 

Intelligent Limiting

.........................................................................5 

 2d 

Soft Knee, Slow Envelope

.............................................................5 

 2e 

Hard Knee, Slow Envelope

............................................................6 

 

3

 

Introduction

......................................................................................6 

 

4

 

Installation

........................................................................................7 

 4a 

Mounting

......................................................................................7 

 4b 

Audio connections

........................................................................7 

 4c 

Power connections

.......................................................................7 

 

5

 

Compressors and Limiters Explained

...............................................8 

 

5a 

What is a Compressor / Limiter?

....................................................8 

 5b 

Threshold Explained

.....................................................................8 

 5c 

What is Hard-Knee and Soft-Knee?

...............................................9 

 5d 

Ratio Explained

............................................................................9 

 5e 

What about Attack and Release Controls?

......................................9 

 5f 

Gain Requirements

.....................................................................10 

 5g 

Understanding Compressor/Limiters Verses Peak Limiting

.............10 

 5h 

Other Nomenclature

...................................................................10 

 

6

 

Control Descriptions

.......................................................................10 

 6a 

Envelope Switch

.........................................................................10 

 6b 

Knee Switch

...............................................................................11 

 6c 

Threshold 

..................................................................................11 

 6d 

Ratio..................................................................................................

11 

 6e 

Gain

..........................................................................................11 

 6f 

Peak ..................................................................................................

11 

 6g 

Bypass Switch...................................................................................

11 

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CX335: 

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CONTENTS (Cont..) 

 
 

Section

 

Page

 

 6h 

Gain Reduction Meter

.................................................................12 

 6i 

Output Level Meter Displays

........................................................12 

 

7

 

Operation

........................................................................................12 

 

8

 

Technical Specification

...................................................................13 

 

9

 

General Specification

......................................................................13

 

 

 

 

 

 

    

 

 

 

 

 

 

 

    

 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

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CX335

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Page 3 

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

• 

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 Quick 

Start 

1.  Connect the unit into the signal path directly after the system mixing desk or DJ console, 

and just before any amplifiers or crossover. 

2.  If your system runs balanced then used balanced XLR leads, with the standard 

configuration of: 

     Pin 2 hot (positive phase); Pin 3 cold (negative phase); Pin 1 ground (screen). 
3.  If you are configured 'unbalanced' then we suggest that the inputs only are wired Pin 2 

hot, with Pin 3 shorted to Pin 1.  Do this, even if you are in a hurry. 

4.  If you are running a mono system you will have to connect the input signal to both 

channels using some form of 'Y' lead. 

 

We have carefully optimised the front panel removing most of the traditional compressor 
limiter controls by making the circuitry 'Programme Dependant'.  To aid setting up the front 
panel controls the common permutations of switches and controls can be placed into four 
different groups, each one having different audio results. 

 

 

Soft Knee, Fast Time Constant (Normal Envelope) (2a):

 

 

 

Ultra transparent Control of Sound Pressure Level (SPL) and speaker protection. 

 

 

Soft Knee, Slow Time Constant (Slow Envelope) (2d): 

 

Very transparent control of SPL with more peaks allowed through unprocessed.

 

 

 

Hard Knee, Fast Time Constant (Normal Envelope) (2b): 

 

Precise control of signal level and speaker protection. 

 

 

Hard Knee, Slow Time Constant (Slow Envelope) (2e):

 

 

The least transparent mode of operation to reduce high level signals but with more peaks 
passed unprocessed. 

 

2a 

       Soft Knee, Fast Time Constant (Normal Envelope) 

 

 

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CX335: 

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This is the recommended mode of operation, yielding the most musical results with the least 
perceptible manipulation of the audio signal.  Release both the envelope and knee switches. 
Set the threshold to somewhere between 10dB and 15dB LOWER than your average input 
level and set the ratio control somewhere between 5:1 and 10:1, if you require compression 
of the audio signal, but 20:1 or higher if you require compression and limiting.  With normal 
programme level running through the CX335, rotate the gain control so that the output level 
on the left and right channel VU meters measures about the same in bypass mode as it does 
with the compressor operational.  

 

With this configuration, the louder the input then the more compression will take place.  A 
distinguishable increase in average overall volume should be noted, although the peak 
output level should be slightly lower. 

The ‘Peak’ control

 operates independently from the compressor/limiter section of the 

CX335. It has the advantage of allowing the user to directly set an absolute limit on the 
maximum output level, however it has the disadvantage of not sounding as transparent as 
the compressor. The compressor should be set to provide most of the gain reduction. The 
peak limiter should be used as a safety net to protect the system when it is under abuse. 
The peak control is best adjusted by using the highest anticipated input level and observing 
the clip or peak indicators of the systems power amplifiers. The ‘Peak’ control should be set 
to prevent any potentially damaging amount of clipping. Note that sometimes, on systems 
with an active crossover, some clipping on the bass amplifiers may be acceptable. 

If the 

peak LED on the CX335 is operating more than occasionally then the unit is not 
adjusted for optimum performance 

and the compressor controls should be adjusted to 

give more gain reduction. 

 

2b 

Hard Knee, Fast Time Constant (Normal Envelope) 

 

 

This mode of operation will be slightly more noticeable (especially with high ratio settings) as 
the point where compression takes effect is at a definite audio level. 
Depress the knee switch and release the envelope switch.  Set the threshold to somewhere 
between 0dB and 8dB LOWER than your maximum input level.  Set the ratio control at about 
5:1 or even higher, if you require compression of the audio signal, but 20:1 or higher if you 
require compression and limiting.  The higher the ratio the more audible the compression. 
Turn the gain control so that the output level on each VU meter reads about the same in 
bypass mode as it does with the compressor operational.  Information on configuring the 
peak control is described in detail in section 2a, page 4. (above). 
With this configuration, quieter signals should pass through the compressor unprocessed, 
(no gain reduction taking place) but louder input signals above the threshold level will have a 
significant amount of compression (L.E.D’S will light on the gain reduction meter).  The peak 
limit LED will flicker ON more often than would normally be expected, especially with very 
percussive tracks at high level.  No perceived effect will be noticed until very high input levels 
are used, then the CX335 will take control to preserve system integrity. 

 
 
 
 

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2c Intelligent 

Limiter 

 

Due to the programme dependant nature of the compressor section and its split frequency 
stereo side chain, the preferred method of limiting is to use the compressor section with a 
ratio of 

 to 1.  Depress the knee switch and release the envelope switch.  Set the threshold 

to the level where limiting is to commence.  Set the ratio control fully clockwise.  Turn the 
gain control so that the output level on the VU meters measures about the same in bypass 
mode as it does with the compressor operational.  Information on configuring the peak 
control is described in detail in section 2a, page 4.

  

 

With this configuration, quieter signals will pass through the compressor unprocessed, (no 
gain reduction taking place) but louder input signals above the threshold level will have a 
definite maximum output level that will never be exceeded (L.E.D’S will light on the gain 
reduction meter).  The peak Limit LED should never flicker if it is set correctly and providing 
that the gain control is not adjusted too high. 

 

2d 

Soft Knee, Slow Time Constant (Slow Envelope) 

 

 

This mode of operation will still yield musical results, but will tend to allow the very quick 
dynamics through unprocessed.  Therefore you will require more peak limiting and a high 
overhead in speaker power handling.  Depress the envelope switch and release the knee 
switch.  Set the threshold to somewhere between 10dB and 15dB LOWER than your 
average input level and set the ratio control somewhere between 5:1 and 10:1, if you require 
compression of the audio signal, but 20:1 or higher if you require compression and limiting. 
With normal programme level running through the CX335, rotate the gain control so that the 
output level on the left and right channel VU meters measures about the same in bypass 
mode as it does with the compressor operational.  Information on configuring the peak 
control is described in detail in section 2a, page 4.

 

With this configuration, the louder the input then the more compression will take place.  A 
perceived increase in average overall volume should be noted, although the peak output 
level should be slightly lower.  Some dynamics might cause other problems further down the 
signal path. 

 

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CX335: 

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2e

 

Hard Knee, Slow Time Constant (Slow Envelope)

 

 

This mode of operation will be the most noticeable (especially with high ratio settings and 
fast dance tracks) as the point where compression takes effect is at a definite audio level. 
Depress the knee and envelope switches.  Set the ratio control at about 5:1 or even higher, if 
you require compression of the audio signal, but 20:1 or higher if you require compression 
and limiting.  The higher the ratio the more audible the compression will be.  
A high ratio setting will allow the threshold control to be set to the maximum input level 
precisely.  As the ratio is decreased the value of the threshold control should be reduced to 
compensate. 
Information on configuring the peak control is described in detail in section 2a, page 4. Turn 
the gain control so that the output level on the VU meters measures about the same in 
bypass mode as it does with the compressor operational. 
With this configuration, quieter signals should pass through the compressor unprocessed, 
(no gain reduction taking place) but louder input signals above the threshold level will have a 
significant amount of compression after the initial peak is passed unprocessed.   

 

PLEASE TAKE SOME TIME TO READ THE REMAINDER OF THE MANUAL 

 

3 Introduction 

The Cloud CX335 Stereo Compressor Limiter has been designed to provide compression of 
full range music signals and also be suitable for overload protection in a wide range of 
applications.  The unit can be applied equally to any discotheque or live installation as well 
as in the recording studio and mastering facility. 

 

Historically, it has often been impossible to establish what time constants are to be applied to 
a compressors attack and release envelope when the signal dynamics are an unknown 
quantity.  The CX335 has intelligent 'Programme Dependant' circuitry, which makes the need 
for attack and release controls totally redundant.  Other features include the options of hard-
knee or soft-knee characteristics, a fully controllable 'Instant-attack' peak limiter, accurate 
and informative metering, and remote control of the compressor side chain. 

 

The CX335 may be used in either balanced or unbalanced systems with no internal re-
configuring. 

 

Because the CX335 compressor offers a choice of traditional hard-knee, ratio style 
compression or soft-knee compression, it is equally adept at creative work and unobtrusive 
level control.  With high ratio settings the compressor can perform the functions of an 
intelligent programme-dependent limiter. 

 

The control layout is simple and logical.  For reasons that will become evident, the unit is 
graduated assuming that of a hard-knee ratio style compressor, although the preferred mode 
of operation is soft-knee where the transition from unity gain to gain reduction at the selected 
ratio is progressive and occurs over a nominal 10dB input level range.  In other words, in 
soft-knee mode with high ratios, the unit will blend from gentle compression up to hard 
limiting with no additional front panel adjustment. 

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Soft-knee compressors are often chosen in applications that call for less conspicuous level 
control whereas ratio type hard knee compressors are generally considered more successful 
where large amounts of gain reduction are required.  By offering both alternatives, the 
CX335 is capable of outstanding results in a very wide range of discotheque, studio and live 
sound situations. 

 

Compressors are often accused of dulling the sound being processed, and a little 
explanation is needed to understand exactly why that is.  Bass frequency sounds, which 
contain most of the energy in a typical piece of music, cause a normal compressor to apply 
gain reduction.  This is fine until quieter, high frequency sounds occur at the same time as 
that bass sound, these high frequencies will also be turned down in level simultaneously with 
the bass and therefore suffer as a consequence.  This is why the cymbals and hi-hats in a 
heavily compressed track seem to dip in level whenever a loud bass drum or snare drum 
beat occurs.  The 'intelligent' side-chain of the CX335 will attempt to overcome this by 
sensing the input frequency of the signal and adjusting itself accordingly. 

 

Another feature of the CX335 is a highly effective peak limiter that allows the user to set an 
absolute output level that can never be exceeded.  This facility is extremely valuable for 
speaker driver protection.  With correct threshold and ratio adjustments the compressor 
section can be set to act as a primary level controller with the peak limiter set above this to 
perform secondary security. 

 

4 Installation 

 

4a Mounting 

The CX335 is designed for standard 19" rack mounting and occupies 1U of rack space. 
Avoid mounting the unit directly above power amplifiers or power supplies that radiate 
significant amounts of heat and strong magnetic fields.  Fibre or plastic washers may be 
used to prevent the front panel becoming marked by the mounting bolts. 

 

4b Audio 

Connections 

The input 3pin XLR connectors may be used either balanced or unbalanced, the wiring 
convention being: pin 2 hot, pin 3 cold and pin 1 ground. For use with unbalanced systems, 
unbalancing can be achieved by shorting pin 3 of the XLR connectors to ground (pin 1) at 
the inputs.  In both modes of operation the systems input level should be referenced to 
0dBu. 

 

The CX335 is designed as a stereo compressor and always expects to be used with 
matching left and right stereo signals.  Unexpected and unusable results will occur if two 
independent mono signals are fed through the unit.  Furthermore, if the audio system being 
processed is configured for mono operation you will have to connect an input signal to both 
channels to make any sense of the front panel meter calibration and control graticules, 
although only one output socket need be used. 

 

If earth loop problems are encountered, do not disconnect the mains earth but instead, 
operate the system in the balanced mode with the cable screen only connected at the 
receiving end of the cables.  If the system can only be operated in the unbalanced mode, 
then we suggest that an audio isolating transformer be used. 
 

UNDER NO CIRCUMSTANCES MUST ANY EARTH CONNECTIONS BE REMOVED.

 

 

4c Power 

Connection 

The unit will have been configured to operate on a power input of 220 to 240 Volts AC at 40 
to 60Hz. If for some reason the unit is to be used at a mains input operating voltage which is 
different to that as supplied, the following procedure must be carried out. 

(See the diagram 

on the following page) 
 
 

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CX335: 

Installation and Operation Manual 

TRANSFORMER

FIT ONE

LINK FOR

220/240
VOLTS

OPERATION

FIT TWO

LINKS FOR

110/120
VOLTS

OPERATION

240V

TRANSFORMER

120V

120V

VIEW INSIDE CX335 SHOWING POSITION OF VOLTAGE SELECTION  LINKS

HIGH VOLTAGE

HIGH VOLTAGE

 

1: Disconnect the unit from the mains. 
2: Using a number 2 size pozidrive screwdriver, remove the six self-tapping screws retaining 
the top panel of the unit. 
3: Using a number 1 size pozidrive screwdriver, remove 4 M3 machine screws that retain the 
main PCB to the bottom panel. These can be located: 
3.1: Just behind the Threshold control 
3.2: Directly behind the Gain Reduction display meter. 
3.3: In front and to the rear of the grey encapsulated transformer block. 
4: From the underside of the unit, remove the six self-tapping screws retaining the bottom 
panel of the unit, using the number 2 pozidrive. 
5a: If the unit is currently configured for 220-240 Volts AC, to the side of the transformer can 
be found 1 zero Ohm link. This should be removed and two zero Ohm links should be fitted 
to the positions marked 110-120 Volts. Go to paragraph 6. 
5b: If the unit is currently configured for 110-120 Volts AC, to the side of the transformer can 
be found 2 zero Ohm links. These should be removed and one zero Ohm link should be 
fitted to the position marked 220-240 Volts. 
6: Replace the power fuse with a correctly rated fuse for the new operating voltage. 
7: Re-fit the two covers in the reverse order. 

 

5  

Compressors and Limiters Explained 

 

5a 

What is a compressor / limiter? 

Compression is an audio process that reduces the output progressively once the input level 
has risen above a pre-settable threshold. Once this threshold level is exceeded then the rate 
at which the output is reduced is controlled by a predictable rate, called 'ratio'. Limiting is an 
extension of compression where once the threshold is exceeded, the output level will not rise 
any further. Therefore limiting can also be perceived as a compressor with its 'ratio' set 
higher than 20 to 1. 

 

5b Threshold 

explained 

As a rotary control, the threshold parameter is easy to understand. Threshold compares the 
input level to the level set on the front panel. It is very common to see the graticule around 
the threshold control marked from higher levels on the counter clockwise end to lower input 
levels on the clockwise end. This is because more compression happens as the control is 
turned 'up'. 

 
 
 
 

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5c 

What is Hard-knee and Soft-knee? 

The actual threshold point where compression takes place is called the 'knee', the reason 
being that if a graphical representation of input level verses output level is made, then below 
threshold the line will be at 45° (output is the same as input). Above threshold this line will 
have a gentler slope equal to the ratio setting. So the line will have a definite 'fold' or 'knee'. 

(See diagram below).

 

With high ratio settings this knee can be very noticeable. To prevent this sudden change 
between no compression below threshold and lots of compression above threshold, it is 
much gentler on the ear if this knee is 'rounded' or softened. Soft-knee is more musical and 
desirable if the actual compression process is not to be too obtrusive. So by default, the 
CX335 compressor limiter is a 'soft-knee' device, yet still can be overridden by use of the 
hard switch. 

 

Graphical Representation of Compression and Limiting 

LIMITING

SOFT KNEE

NO COMPESSION

HARD KNEE

GRAPH OF INPUT LEVEL

VERSES OUTPUT LEVEL

THRESHOLD

OUTPUT IN dBs

INPUT
IN dBs

-10

-5

0dB

+5

+10

-15

-20

-25

-30

-10

-5

0dB

+5

+10

-15

-20

-25

-30

RATIO  20:1 OR GREATER

RATIO  10:1 OR LESS

 

5d Ratio 

explained. 

For a hard-knee compressor, the effect of Ratio can be easily understood by remembering 
that ratio is a comparison between input levels and output levels. For instance; a ratio setting 
of 3:1 results in only 1dB of change at the output for every rise in input level by 3dB providing 
that the input is greater than the threshold setting. A simple rule of reading Ratio settings can 
be input:output, or input rise of 

x

dB gives output rise of 

y

dB. For a soft-knee compressor, the 

Ratio control becomes a little less well defined 
Soft-knee gradually changes the ratio as the signal rises above the threshold setting. On the 
CX335 this change takes place for as much as 10dBs, so the selected ratio is only reached 
once the signal is 10dB above the threshold setting. This changing ratio is far more musical 
and disguises the fact that any manipulation of the dynamic range is taking place. 

 

5e 

What about Attack and Release controls? 

The rate at which the compressor takes effect (once the threshold is exceeded) is called 
Attack, similarly the rate at which the compressor subsides (after the input signal falls below 
threshold) is called Release. The wrong attack time for a compressor will have different poor 
results for differing input frequencies. For instance too fast an attack time with low 
frequencies will cause distortion as the gain reduction changes during one cycle.  On the 
contrary, too slow an attack time on high frequencies will not process the signal peaks quick 
enough, resulting in the possibility of system clipping and lack of speaker protection. 
The conclusion is that for broadband music programme a fixed attack time is virtually 
useless. Similarly a release control that doesn't track the input programme envelope will 
result in audible 'pumping' or breathing as the gain reduction changes. The CX335 gets over 
this problem by constantly adjusting these two crucial 'parameters' internally depending on 

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CX335: 

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the level and frequency of the incoming signal. For this reason the Attack and Release 
controls have been removed from the front panel. 

 

5f Gain 

requirements 

When the signal exceeds threshold and the compressor takes effect, there will be a 
reduction in the real output 'volume'. This volume reduction is made back up to the original 
level with the Gain control. In normal use, the average amount of level reduction shown on 
the gain reduction meter, will be the position to where the Gain control is rotated positively. A 
point to note is that this gain is applied to all signals, whether above or below any thresholds, 
so quiet sounds will be louder by the amount of gain make-up, even the residual background 
system noise! 

 

5g 

Understanding Compressor Limiters verses Peak limiting 

Due to the range of the ratio control, the compressor can be set up to perform as a very 
effective limiter. Further more, with its soft knee operation, the characteristics of the unit 
blend from gentle compression for signal just above threshold, through to hard limiting. The 
intelligent control circuitry and programme dependent attack and release make the audible 
effect almost un-noticeable. This compressor limiter section should not be confused with the 
Peak limiter in the CX335. This is intended to be used as a system failsafe for any high 
peaks that are still quite high even after some compression has occurred. 
For example, with signals above the compressor threshold, if the ratio is set to 3:1 and the 
input rises by +15dB there will still be a +5dB rise at the output. This rise might cause a 
system overload, except this can be trapped by the Limiter section providing the Peak Limit 
threshold is correctly adjusted. The optimum use of the Peak Limiter is when used in this 
method. It is difficult to give a generalisation for limiter threshold settings as many factors 
govern this value: 
Firstly, how much level can be sent from the mixing console? In a well configured system this 
will average around 0dB, but with only slightly too much gain at each mixing stage this level 
can soon rise far higher. The Peak limiter can be set to capture this overload. 
Secondly, how much signal is required by the amplifier or crossover inputs? If the Peak 
Limiter is set too high then any peaks allowed through the CX335 might cause input 
distortion or overload to the following amplifier. It is more likely that the amplifiers will clip 
before the output signal clips 

 

5h Other 

nomenclature. 

Side-Chain - The control circuit that decides how much gain reduction to apply at any one 
instant, depending on the input level and the front panel controls is called the side-chain. In a 
standard compressor the circuitry only has two main sections: the audio path and the side 
chain. 
Gain Reduction - The difference between the measured output level after the compressor 
has taken effect and the level that would be output if no processing were happening. 

 

6 Control 

Descriptions 

 

 

 

6a            Envelope switch

 

In the slow position it modifies the programme-dependant circuitry to allow fast dynamic 
peaks through unprocessed, yet still monitor and control level when the input is above the 

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threshold for periods of a second or more.  If this switch is depressed it is strongly advised 
that the peak limiter should be used as an additional tool to restrain very loud and quick 
dynamic peaks. 

 

6b            Knee switch

 

In the hard position it modifies the knee of the compressor by affecting the ratio control so 
that gain reduction takes place linearly once the threshold level is exceeded.  It is strongly 
advised that the unit be configured in its intended mode of soft-knee for a more transparent 
compression. 

 

6c            Threshold

 

This control determines the input level above which gain reduction will be applied and may 
be set in the range +10dB to -20dB.  This control graticule is accurate for compression with 
the knee switch depressed.  In the soft-knee mode, compression takes place gradually once 
the threshold is just exceeded.  The amount of compression rises, until the input signal 
reaches approximately 10dB above the threshold setting, where upon conventional 
compression is applied at the amount dictated by the ratio control. 

 

6d            Ratio

 

With the knee switch depressed, this control governs by how much the input level must rise 
before a rise of 1dB would be seen at the output.  For example, (In hard-knee mode) with the 
input signal level above the threshold setting, a ratio setting of 5:1 would imply that the 
output would only rise by 1dB with a 5dB rise in the input level. 
With the compressor set for soft-knee, ratio fixes the final compression ratio that will be 
applied once the 10dB soft-knee region is exceeded.  The ratio may be continuously 
adjusted from 1.2:1 to 

: 1 allowing the possibility of true hard limiting. 

 

6e            Gain  

The output level may be attenuated or amplified by up to 12dB to compensate for level 
changes caused by compression and limiting.  Quite often compressors are perceived to 
'reduce' the total output level, this control should normally be adjusted so that the output 
level measures identical levels on the VU meters with bypass depressed and released.  The 
gain control can also be set audibly if the system speakers are within unobstructed earshot. 
Normally this control will be operated rotated to the positive (clockwise) gain side. 
This control comes before the peak limiter detector and this fact should be taken into 
account when setting the peak limiter threshold. 

 

6f            Peak Limit

 

Sets an absolute limit to the level that the output signal will not be permitted to exceed.  The 
control ranges from +26dBu (where the limiter has no effect) down to -6dBu.  This limiter is 
very fast acting enabling it to control any peaks without audible distortion.  If the output signal 
is so high as to cause the limiter to operate for more than 20mS, the system gain is 
automatically reduced to bring the signal back within range.  The system gain is then 
returned to normal over a period of approximately one-second.  The peak limit control and 
the compressor gain control should be used in conjunction to ensure that the peak limiter 
operates only rarely (if at all), if it is to be used purely for peak protection.  

 

6g Bypass 

This switch causes a bypass of all signal processing, where the input signal is routed directly 
to the output socket.  Normally the switch is used to compare the raw unprocessed signal 
against the effects of any compression and or limiting. 

 
 
 
 
 
 
 

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CX335: 

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6h 

Gain Reduction Meter

 

 

A nine-segment LED bar graph meter continuously monitors the gain reduction applied by 
the compressor and or limiter and even any remote control voltage over the range 0 to 30dB. 
The amount of gain reduction shown is greatly affected by all of the front panel controls.   

 

6i 

Output Level Meters

 

These are nine segment LED bar graph level meters, that monitor the level of the two output 
signals over the range -20dB to +12dB with reference to the 0dBu operating level.  With 
average stereo programme these will track together.  Vastly differing levels will most likely be 
a cable short or external system configuration fault. 

 

7 Operation 

The unit should be connected in line with the stereo signals to be processed either by 
breaking the existing connection between mixer console and cross-over or amplifiers or via 
suitable insert points on the master outputs of the console (if such exist). 
Setting up the front panel controls is easiest if the peak limiter threshold is initially set to 
maximum.  This allows the compressor to be set up in isolation.  The ratio setting depends 
on how firmly the signal dynamics need controlling; commonly, higher ratios provide a higher 
degree of control but also tend to be more audible in operation when high levels of gain 
reduction are required.  The integral soft-knee feature of the CX335 renders these effects far 
less pronounced, but this factor should still be taken into consideration when setting up. 
Although, with the CX335 a higher compression ratio may be used than that of conventional 
compressors without compromising the sound quality. 

 

Adjust the threshold control until the desired amount of gain reduction occurs.  This is judged 
partly by ear and partly by observing the gain reduction meter.  In general, a maximum gain 
reduction of between 6dB and 10dB will be adequate.  When in the soft knee mode, you will 
notice that the threshold control is rotated clockwise more than would normally be expected. 

 

Set the gain control to give the required output level using the level meter to guide you. 
Additional assistance can be obtained by toggling between bypass mode and normal 
compressor operation, in both modes the optimum gain setting will give equal output levels 
on the meter, but a slight increase in the 'music power' with the compressor operating.  Avoid 
running at very high output levels as this reduces the available amount of signal headroom 
and could lead to distortion in extreme cases.  

 

Once the gain is correct, set the peak limiter level control so that the limiter LED only lights 
briefly on extreme signal peaks.  Alternatively, set the peak limiter level to the desired 
maximum output value and then adjust the compressor gain control to ensure minimum 
limiter activity.  One major use of the peak limit control is to prevent input distortion or 
clipping on the following amplifiers.  If only peak limiting is required then we suggest setting 
the compressor ratio to greater than 1:20, the compressor threshold to at least 12dB lower 
than the normal input level and using the soft-knee mode as opposed to using the peak 
limiter alone. 

 

The peak limiter has no separate on / off control, but turning the peak Level control fully 
clockwise will prevent any unwanted limiter action.  To effectively bypass the compressor 
section turn the compressor threshold up to its maximum of +10dB (fully counter-clockwise) 

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and set the ratio to its lowest setting of 1.2:1 although we do not recommend using the peak 
limiter without the support of the compressor section. 

 

8 Technical 

Specifications 

 

INPUT IMPEDANCE 

10k

 

MAXIMUM INPUT LEVEL 

+26dBu 

OUTPUT IMPEDANCE 

80 

 

MAXIMUM OUTPUT LEVEL 

+26dBu 

MINIMUM OUTPUT LOAD 

600

 

FREQUENCY RESPONSE 

20Hz to 20kHz ±0.5dB 

CROSSTALK 

<-70dB 10kHz 

(All measurements referenced to 0dBu operating level) 

 

NOISE AT UNITY GAIN 

22Hz - 22KHz 

-90dB

 

CCIR ARM 

-90dB

 

IEC A

 

-92dB 

 

DISTORTION (THD and NOISE) 

 

100Hz 1KHz 10KHz 

Unity Gain, 0dBu 

<0.03% <0.02% <0.03% 

+10dBu input 10db Gain Red 

<0.1% <0.1% <0.1% 

 

9 General 

Specifications 

 

POWER REQUIREMENTS

 

110-120 Volt or 220-240 Volt at 40-60Hz, 15 Watts 

FUSE RATING

 

100mA for 220-240 Volts, 200mA for 120 Volts 

FUSE TYPE

 

20mm x 5mm, Class 3 type 'T' (time delay), 250 Volts working 

CASE SIZE

 

482mm (w) x 44mm (h) x 155mm (d) 

WEIGHT

 

3.4 kg’s (including packaging) 

 

 

 

 

 

 

 

 

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. 

 

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

 

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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. 

 

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