Alesis CLX440 User manual

CLX-440 Reference Manual 1
Compressor / Limiter / Expander
Reference
Manual
2001

CLX-440 Manual
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CLX-440 Manual
CLX-440 Reference Manual 3
Contents
Contents........................................................................................................................3
Welcome!.....................................................................................................6
How to Use This Manual .........................................................................7
Important Safety Instructions..................................................................8
CE Declaration of Conformity...............................................................10
Instructions to the User (FCC Notice)..................................................14
Quick Start Guide .....................................................................................................15
If you can't wait to get started:..............................................................15
Step 1: Hook it up to a mixer ........................................................15
Step 2: Try some compression ......................................................16
Step 3: Try some gating..................................................................17
Connections...............................................................................................................19
Unpacking and Inspection.....................................................................19
Installing in a Rack ..................................................................................19
Power .........................................................................................................20
Connecting inputs and outputs ............................................................22
Connecting to the Channel Inserts of a mixing console: .........22
Connecting to the Main Inserts of a mixing console: ...............23
Connecting to the inserts on an instrument amplifier:............24
Connecting to equipment with XLR inputs and outputs:.......24
About Audio Cables................................................................................25
Dual Channel Operation ........................................................................26
Basics of Compression............................................................................................27
What is compression? .............................................................................27
Description of Controls ..........................................................................28
Threshold .......................................................................................28
Ratio ................................................................................................29
Attack..............................................................................................29
Release............................................................................................29
Detect ..............................................................................................29
Knee ................................................................................................30
Compression Artifiacts...........................................................................31
Pumping and Breathing..............................................................31
Clicking or "Zipper Noise" .........................................................31
Reduced Gain Structure ..............................................................31

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Limiting .....................................................................................................32
Limiter Threshold.........................................................................32
Stereo Detection .......................................................................................33
Look Ahead Compression .....................................................................33
Sidechain ...................................................................................................34
Basics of Expansion.................................................................................................35
What is expansion?..................................................................................35
Description of Controls ..........................................................................36
Threshold .......................................................................................36
Ratio ................................................................................................36
Knee ................................................................................................37
Attack..............................................................................................37
Hold ................................................................................................37
Release............................................................................................38
Keyed Expansion .....................................................................................39
App ications...............................................................................................................41
Compressor Applications ......................................................................41
Vocal Limiting...............................................................................41
Vocal Compression ......................................................................42
Drums.............................................................................................42
Bass..................................................................................................43
Electric Guitar ...............................................................................43
Compressor Applications using the Sidechain..................................44
De-essing........................................................................................44
Ducking..........................................................................................45
Expander Applications...........................................................................46
Gating a Noisy Guitar Amp .......................................................46
Expanding Live Vocal Tracks ....................................................46
Expander Applications using the Key.................................................47
Gated Reverb.................................................................................47
Key Filtering for a Tom Mic gate...............................................48
Staccato Gating a Synth Pad.......................................................49
Troub eshooting.......................................................................................................51
Troubleshooting Index ...........................................................................51
Avoiding ground loop noise ......................................................52
Line Conditioners and Protectors .............................................53
Care and Maintenance............................................................................54
Cleaning .........................................................................................54
Refer All Servicing to Alesis.......................................................54
Obtaining Repair Service ............................................................55
Specifications............................................................................................57

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Audio Input .................................................................................57
Sidechain/ Key Inputs...............................................................57
Direct Output...............................................................................57
Audio Output..............................................................................57
Audio Performance ....................................................................57
Mechanical ...................................................................................58
A esis Limited Warranty.........................................................................................59

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Welcome!
Thank you for making the Alesis CLX-440™ a part of your
studio. Since 1984, we've been designing and building creative
tools for the audio community. We believe in our products,
because we've heard the results that creative people like you
have achieved with them. One of Alesis' goals is to make high-
quality studio equipment available to everyone, and this
Reference Manual is an important part of that. After all, there's
no point in making equipment with all kinds of capabilities if no
one explains how to use them. So, we try to write our manuals
as carefully as we build our products.
The goal of this manual is to get you the information you need as
quickly as possible, with a minimum of hassle. We hope we've
achieved that. If not, please drop us an email and give us your
suggestions on how we could improve future editions of this
manual.
We hope your investment will bring you many years of creative
enjoyment and help you achieve your goals.
Sincerely,
The people of Alesis Studio Electronics

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How to Use This Manual
This manual is divided into the following sections describing the
various functions and applications for the CLX-440. While it's a
good idea to read through the entire manual once carefully,
those having general knowledge about studio equipment should
use the table of contents to look up specific functions.
Chapter 1: Quick Start. If you're already familiar with
recording, this will get you started using the CLX-440 right
away. It's a short guide to the essential elements of connections
and operation.
Chapter 2: Connections. This section gives detailed instructions
for connecting the CLX-440 to a variety of typical audio systems.
Chapter 3: Basics of Compression. This section explains what a
compressor does and explains the function of each of the
controls.
Chapter 4: Basics of Expansion. This chapter explains the other
major feature of the CLX-440, expansion, and each of the front
panel controls dedicated to this function.
Chapter 5: Applications. Skip to this section for tips on using the
CLX-440 with a variety of audio sources.
Chapter 6: Troubleshooting. Refer to this chapter if you
experience any problems while using the CLX-440.
Helpful tips and advice are highlighted in a shaded box like this.
The names of specific controls or connectors on the CLX-440 are
printed in a special font, i.e., the BYPASS button.
✪When something important appears in the manual, an icon
(like the one on the left) will appear in the left margin. This
symbol indicates that this information is vital when operating
the CLX-440.

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Important Safety Instructions
Safety symbols used in this product:
This symbol alerts the user that there are important
operating and maintenance instructions in the literature
accompanying this unit.
This symbol warns the user of uninsulated voltage within
the unit that can cause dangerous electric shocks.
This symbol warns the user that output connectors contain
voltages that can cause dangerous electrical shock.
Please follow these precautions when using this
product:
1. Read these instructions.
2. Keep these instructions.
3. Heed all warnings.
4. Follow all instructions.
5. Do not use this apparatus near water.
6. Clean only with a damp cloth. Do not spray any liquid cleaner
onto the faceplate, as this may damage the front panel controls
or cause a dangerous condition.
7. Install in accordance with the manufacturer's instructions.
8. Do not install near any heat sources such as radiators, heat
registers, stoves, or other apparatus (including amplifiers) that
produce heat.
9. Do not defeat the safety purpose of the polarized or grounding-
type plug. A polarized plug has two blades with one wider than
the other. A grounding-type plug has two blades and a third
grounding prong. The wide blade or the third prong are
provided for your safety. When the provided plug does not fit

CLX-440 Manual
CLX-440 Reference Manual 9
into your outlet, consult an electrician for replacement of the
obsolete outlet.
10. Protect the power cord from being walked on or pinched,
particularly at plugs, convenience receptacles, and the point
where they exit from the apparatus.
11. Use only attachments or accessories specified by the
manufacturer.
12. Use only with a cart, stand, bracket, or table designed for use
with professional audio or music equipment. In any installation,
make sure that injury or damage will not result from cables
pulling on the apparatus and its mounting. If a cart is used, use
caution when moving the cart/apparatus combination to avoid
injury from tip-over.
13. Unplug this apparatus during lightning storms or when unused
for long periods of time.
14. Refer all servicing to qualified service personnel. Servicing
is required when the apparatus has been damaged in any way,
such as when the power-supply cord or plug is damaged, liquid
has been spilled or objects have fallen into the apparatus, the
apparatus has been exposed to rain or moisture, does not
operate normally, or has been dropped.
15. This unit produces heat when operated normally. Operate in a
well-ventilated area with at least six inches of clearance from
peripheral equipment.
16. This product, in combination with an amplifier and headphones
or speakers, may be capable of producing sound levels that
could cause permanent hearing loss. Do not operate for a long
period of time at a high volume level or at a level that is
uncomfortable. If you experience any hearing loss or ringing in
the ears, you should consult an audiologist.
17. Do not expose the apparatus to dripping or splashing. Do not
place objects filled with liquids (flower vases, softdrink cans,
coffee cups) on the apparatus.
18. WARNING: To reduce the risk of fire or electric shock, do not
expose this apparatus to rain or moisture.

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Instructions de Sécurité Importantes (French)
Symboles utilisés dans ce produit
Ce symbole alèrte l’utilisateur qu’il existe des instructions de
fonctionnement et de maintenance dans la documentation jointe avec
ce produit.
Ce symbole avertit l’utilisateur de la présence d’une tension
non isolée à l’intérieur de l’appareil pouvant engendrer des chocs
électriques.
Ce symbole prévient l'utilisateur de la présence de tensions
sur les raccordements de sorties, représentant un risque
d'électrocution.
Veuillez suivre ces précautions lors de l’utilisation de l’appareil:
1. Lisez ces instructions.
2. Gardez ces instructions.
3. Tenez compte de tous les avertissements.
4. Suivez toutes les instructions.
5. N’utilisez pas cet allareil à proximité de l’eau.
6. Ne nettoyez qu’avec un chiffon humide. Il est potentiellement
dangereux d'utiliser des pulvérisateurs ou nettoyants liquides
sur cet appareil.
7. Installez selon les recommandations du constructeur.
8. Ne pas installer à proximilé de sources de chaleur comme
radiateurs, cuisinière ou autre appareils (don’t les
amplificateurs) produisant de la chaleur.
9. Ne pas enlever la prise de terre du cordon secteur. Une prise
murale avec terre deux broches et une troisièrme reliée à la terre.
Cette dernière est présente pour votre sécurité. Si le cordon
secteur ne rentre pas dans la prise de courant, demandez à un
électricien qualifié de remplacer la prise.

CLX-440 Manual
CLX-440 Reference Manual 11
10. Evitez de marcher sur le cordon secteur ou de le pincer, en
particulier au niveau de la prise, et aux endroits où il sor de
l’appareil.
11. N’utilisez que des accessoires spécifiés par le constructeur.
12. N’utilisez qu’avec un stand, ou table conçus pour l’utilisation
d’audio professionnel ou instruments de musique. Dans toute
installation, veillez de ne rien endommager à cause de câbles qui
tirent sur des appareils et leur support.
13. Débranchez l’appareil lors d’un orage ou lorsqu’il n’est pas
utilisé pendant longtemps.
14. Faites réparer par un personnel qualifié. Une réparation est
nécessaire lorsque l’appareil a été endommagé de quelque sorte
que ce soit, par exemple losrque le cordon secteur ou la prise
sont endommagés, si du liquide a coulé ou des objets se sont
introduits dans l’appareil, si celui-ci a été exposé à la pluie ou à
l’humidité, ne fonctionne pas normalement ou est tombé.
15. Puisque son fonctionement normale génère de la chaleur, placez
cet appareil au moins 15cm. des équipments péripheriques et
assurez que l’emplacement permet la circulation de l’air.
16. Ce produit, utilisé avec un amplificateur et un casque ou des
enceintes, est capable de produite des niveaux sonores pouvant
engendrer une perte permanente de l’ouïe. Ne l’utilisez pas
pendant longtemps à un niveau sonore élevé ou à un niveau non
confortable. Si vous remarquez une perte de l’ouïe ou un
bourdonnement dans les oreilles, consultez un spécialiste.
Beim Benutzen dieses Produktes beachten Sie bitte
die folgenden Sicherheitshinweise: (German)
1. Lesen Sie die Hinweise.
2. Halten Sie sich an die Anleitung.
3. Beachten Sie alle Warnungen.
4. Beachten Sie alle Hinweise.
5. Bringen Sie das Gerät nie mit Wasser in Berührung.

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12 CLX-440 Reference Manual
6. Verwenden Sie zur Reinigung nur ein weiches Tuch. Verwenden
Sie keine flüssigen Reinigungsmittel. Dies kann gefährliche
Folgen haben.
7. Halten Sie sich beim Aufbau des Gerätes an die Angaben des
Herstellers.
8. Stellen Sie das Gerät nich in der Nähe von Heizkörpern,
Heizungsklappen oder anderen Wärmequellen (einschließlich
Verstärkern) auf.
9. Verlegen Sie das Netzkabel des Gerätes niemals so, daß man
darüber stolpern kann oder daß es gequetscht wird.
10. Benutzen Sie nur das vom Hersteller empfohlene Zubehör.
11. Verwenden Sie ausschließlich Wagen, Ständer, oder Tische, die
speziell für professionelle Audio- und Musikinstrumente
geeignet sind. Achten Sie immer darauf, daß die jeweiligen
Geräte sicher installiert sind, um Schäden und Verletzungen zu
vermeiden. Wenn Sie einen Rollwagen benutzen, achten Sie
darauf, das dieser nicht umkippt, um Verletzungen
auszuschließen.
12. Ziehen Sie während eines Gewitters oder wenn Sie das Gerät
über einen längeren Zeitraum nicht benutzen den Netzstecher
aus der Steckdose.
13. Die Wartung sollte nur durch qualifiziertes Fachpersonal
erfolgen. Die Wartung wird notwendig, wenn das Gerät
beschädigt wurde oder aber das Stromkabel oder der Stecker,
Gegenstände oder Flüssigkeit in das Gerät gelangt sind, das
Gerät dem Regen oder Feuchtigkeit ausgesetzt war und deshalb
nicht mehr normal arbeitet oder heruntergefallen ist.
14. Dieses Gerät produziert auch im normalen Betrieb Wärme.
Achten Sie deshalb auf ausreichende Lüftung mit mindestens 15
cm Abstand von anderen Geräten.
15. Dieses Produkt kann in Verbindung mit einem Verstärker und
Kopfhörern oder Lautsprechern Lautstärkepegel erzeugen, die
anhaltende Gehörschäden verursachen. Betreiben Sie es nicht
über längere Zeit mit hoher Lautstärke oder einem Pegel, der
Ihnen unangenehm is. Wenn Sie ein Nachlassen des Gehörs
oder ein Klingeln in den Ohren feststellen, sollten Sie einen
Ohrenarzt aufsuchen.

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CE Declaration of Conformity
See the Internet site:
www.alesis.com

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14 CLX-440 Reference Manual
Instructions to the User (FCC Notice)
This equipment has been tested and found to comply with the
limits for a class B digital device, pursuant to Part 15 of the FCC
Rules. These limits are designed to provide reasonable
protection against harmful interference in a residential
installation. This equipment generates, uses, and can radiate
radio frequency energy and, if not installed and used in
accordance with the instructions, may cause harmful
interference to radio communications. However, there is no
guarantee that interference will not occur in a particular
installation. If this equipment does cause harmful interference to
radio or television reception, which can be determined by
turning the equipment off and on, the user is encouraged to try
and correct the interference by one or more of the following
measures:
1. Reorient or relocate the receiving antenna.
2. Increase the separation between the equipment and receiver.
3. Connect the equipment into an outlet on a circuit different
from that to which the receiver is connected.
4. Consult the dealer or an experienced radio/TV technician
for help.
This equipment has been verified to comply with the limits for a
class B computing device, pursuant to FCC Rules. In order to
maintain compliance with FCC regulations, shielded cables must
be used with this equipment. Operation with non-approved
equipment or unshielded cables is likely to result in interference
to radio and TV reception. The user is cautioned that changes
and modifications made to the equipment without the approval
of manufacturer could void the user’s authority to operate this
equipment.

Chapter 1
CLX-440 Reference Manual 15
Quick Start Guide
If you can't wait to get started:
The Alesis CLX-440™ is a unique product, but its basic hookup
and operation is similar to other compressors in most respects.
If you're experienced with signal processors, this chapter is a
"shorthand" guide for those who want to start using the CLX-440
right away. If you have questions about any of the features,
don’t worry – later chapters will unveil the mysteries of the
CLX-440's special features.
✪If you're new to signal processing, start with the more detailed
instructions for hookup and operation starting in the next
chapter.
Step 1: Hook it up to a mixer
1. Pull the CLX-440 out of the package.
2. Plug the POWER jack on the back of the CLX-440 into a
grounded AC power source with the supplied power cable.
Press the POWER button to turn it off.
3. Using a pair of insert cables, plug the insert sends of the
mixer to the CHAN A INPUTS on the back of the CLX-440.
4. Connect the insert cable return plugs to the CHAN A OUTPUTS
of the CLX-440.
5. Press the POWER switch on the front of the CLX-440 to
power up the unit.
For more information on connecting the CLX-440, see chapter 2:
Connections.

quick start guide • chapter 1
16 CLX-440 Reference Manual
Step 2: Try some compression
Play some signal into the unit
While learning the unit, you should play a CD or a multitrack
source into the compressor. Choose a song or part that doesn’t
change much, so that you can take your time experimenting with
the different features.
1. Turn the CHAN A INPUT all the way down so that you don’t
distort the unit.
2. Begin playing your source material. Turn the INPUT knob
clockwise until the average level is around –15 on the INPUT
meter. Make sure that the EXPANDER RATIO knob (bottom
row) is set to 1:1
3. Set the compressor RATIO knob (top row) to 1:1. Adjust the
OUTPUT knob so that the OUTPUT meter matches the INPUT
meter.
4. Set the compressor RATIO knob to 6:1 or higher. Set the
THRESHOLD knob at 0dBfs and gradually turn it down. You
will notice the lower you set the threshold, the more the
GAIN REDUCTION meter will light.
5. Press the BYPASS button to hear your signal without the
compression effect. Press it again to return to the
compressed signal.
If you aren’t hearing any effect, try turning the ATTACK and
RELEASE knobs to their fastest settings. If you still can’t hear
anything, turn the RATIO knob to a higher setting.

chapter 1 • quick start guide
CLX-440 Reference Manual 17
Step 3: Try some gating
Find a "peaky" signal
For this exercise, you’ll need some signal that has a lot of peaks.
For example, a full mix with a drum part, a jangly guitar part, or
a conga with room reverb on it. This will show you how to set
the controls so that only the peaks go through the unit.
1. Set the expander RATIO (bottom row) to infinity to 1 (∞:1).
Set the ATTACK, HOLD knobs to their minimum settings and
the RELEASE knob at 12 o’clock.
2. Begin playing your source material. Turn the INPUT knob
clockwise until the average level is around –15 on the INPUT
meter. Set the COMPRESSION RATIO at 1:1. Adjust the OUTPUT
knob so that the OUTPUT meter matches the INPUT meter.
3. Set the expander THRESHOLD knob at 0dBfs. The gain
expansion meter should be fully lit and no signal should
pass through the unit. Now, gradually turn down the
threshold. You should be able to find a range where only the
peaks come through and clamp the music shut on the beat.
4. Press the BYPASS button to hear your signal without the
gated effect. Press it again to return to the gated signal.
This effect is especially fun on dance music.

quick start guide • chapter 1
18 CLX-440 Reference Manual
Front Panel Diagram
1 Sec
1 Sec
1 Sec
1 Sec
-50dBFS
-50dBFS
Rear Panel Diagram

Chapter 2
CLX-440 Reference Manual 19
Connections
Unpacking and Inspection
Your CLX-440 was packed carefully at the factory. The shipping
carton was designed to protect the unit during shipping. Please
retain this container in the highly unlikely event that you need to
return the CLX-440 for servicing.
The shipping carton should contain the following items:
• CLX-440 with the same serial number as shown on shipping
carton
• Power Cable
• This instruction manual
Installing in a Rack
The CLX-440 may be simply set on a table, or installed in a
standard 19" audio equipment rack. The rack ears are integral to
the unit.
Thermal Considerations in Rack Mounting
The CLX-440 can be mounted in an equipment rack (taking
up 2 rack spaces) or placed on a table or shelf. When you
install it, keep in mind that heat is the major enemy of
electronic equipment. Please observe the following:
• The CLX-440 is designed to perform properly over a range of
ambient temperatures from 10° C to +40° C (50° F to 104° F),
in up to 80% non-condensing humidity. These are not
absolute limits, but Alesis cannot guarantee that the CLX-440
will meet its published specs or remain reliable if operated
outside of these ranges.
• Always allow adequate ventilation behind the CLX-440. Do
not seal any enclosure that holds the CLX-440. It is not
necessary to leave an empty rack space above or below the
CLX-440 unless it runs hot enough to affect equipment
above or below it. If your environment is unusually warm
and not air conditioned, space between units will help the
units run cooler.

connections • chapter 2
20 CLX-440 Reference Manual
Power
Make sure you read the initial Important Safety Instructions
chapter at the front of this manual.
AC Power Hookup
Plug the female end of the power cord into the CLX-440’s POWER
INPUT socket and the male (plug) end into a good quality, noise-
free AC power source of the proper rating.
Tip: It’s good practice to not turn on the CLX-440 until all other
audio cables are hooked up as well. Make sure your amplifier
or powered speakers are switched off when turning the CLX-
440 on or off to avoid damage.
The CLX-440 works with any standard line voltage from 100 to
230 volts and comes with a detachable AC line cord suitable for
the destination to which the unit is shipped.
AC Grounding
The line cable is an IEC-spec AC power cable designed to be
connected to a grounded 3-pin outlet, with the third, round pin
connected to ground. Do not substitute any other type of AC
cord; IEC-spec cables of various lengths may be purchased from
electronics stores or your Alesis dealer.
The ground connection is an important safety feature designed
to keep the chassis of electronic devices such as the CLX-440 at
ground potential. Unfortunately, the presence of a third pin does
not always indicate that an outlet is properly grounded. You
may use an AC line tester to determine this. If the outlet is not
grounded, consult with a licensed electrician. When AC currents
are suspected of being highly unstable in VAC and Hz, a
professional power conditioner should be used.