Alto CLE8.0 User manual

User's Manual
LTO
R
www.altoproaudio.com
Version 2.1 Dec. 2002
English
CLE8.0 COMPRESSOR /LIMITER /GATE

1
SAFETY RELATED SYMBOLS
CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN
Protective Ground Terminal
AC mains (Alternating Current)
Hazardous Live Terminal
ON: Denotes the product is turned on.
OFF: Denotes the product is turned off.
WARNING
Describes precautions that should be observed to
prevent the possibility of death or injury to the user.
CAUTION
Describes precautions that should be observed to
prevent damage to the product.
Always use proper ready-made insulated mains
cabling (power cord). Failure to do so could result
in shock/death or fire. If in doubt, seek advice from
a registered electrician.
To prevent fire and damage to the product, use only
Always install in accordance with the manufacturer's
instructions.
Keep product away from naked flames.
IMPORTANT SAFETY INSTRUCTIONS
Read these instructions
Follow all instructions
Keep these instructions. Do not discard.
Heed all warnings.
Only use attachments/accessories specified by the
manufacturer.
Do not tamper with the power cord or plug. These are
designed for your safety.
Do not remove Ground connections!
Protect the power cord and plug from any physical
stress to avoid risk of electric shock.
Do not place heavy objects on the power cord. This
could cause electric shock or fire.
WARNING
the recommended fuse type as indicated in this manual.
Do not short-circuit the fuse holder. Before replacing the
fuse, make sure that the product is OFF and disconnected
from the AC outlet.
Protective Ground
Operating Conditions
Power Cord and Plug
Cleaning
Servicing
Power Supply
External Connection
Do Not Remove Any Covers
Fuse
Refer all servicing to qualified service personnel only. Do
not perform any servicing other than those instructions
contained within the User's Manual.
When required, either blow off dust from the product or
use a dry cloth.
Do not use any solvents such as Benzol or Alcohol.
For safety, keep product clean and free from dust.
If the plug does not fit your AC outlet seek advice from a
qualified electrician.
To avoid the risk of electric shock and damage, do not
subject this product to any liquid/rain or moisture. Do
not use this product when in close proximity to water.
Do not install this product near any direct heat source.
Do not block areas of ventilation. Failure to do so could
result in fire.
Never cut internal or external Ground wires. Likewise,
never remove Ground wiring from the Protective Ground
Terminal.
Before turning the product ON, make sure that it is
connected to Ground. This is to prevent the risk of
electric shock.
Covers should be removed by qualified service
personnel only.
Within the product are areas where high voltages may
present. To reduce the risk of electric shock do not remove
any covers unless the AC mains power cord is removed.
Ensure that the mains source voltage (AC outlet) matches
the voltage rating of the product. Failure to do so could
result in damage to the product and possibly the user.
Unplug the product before electrical storms occur and
when unused for long periods of time to reduce the risk of
electric shock or fire.
No user serviceable parts inside.
This symbol, wherever used, alerts you to impo-
rtant operating and maintenance instructions.
Please read.
This symbol, wherever used, alerts you to the pre-
sence of un-insulated and dangerous voltages with-
in the product enclosure. These are voltages that
may be sufficient to constitute the risk of electric
shock or death.

PREFACE
Dear Customer:
Thanks for choosing LTO CLE 8.0 Compressor/Limter/Gate and thanks for choosing one of the results of LTO
AUDIO TEAM job and researches.
For our LTO AUDIO TEAM, music and sound are more than a job...are first of all passion and let us say...our obsession!
We have been designing professional audio products for a long time in cooperation with some of the major brands in
the world in the audio field.
The LTO line presents unparalleled analogue and digital products made by Musicians for Musicians in our R&D
Centers in Italy, Netherlands, United Kingdom and Taiwan. The core of our digital audio products is a sophisticated
DSP (Digital sound processor) and a large range of state of the art algorithms which have been developed by our
Software Team for the last 7 years.
Because we are convinced you are the most important member of LTO AUDIO TEAM and the one confirming the
quality of our job, we like to share with you our work and our dreams, paying attention to your suggestions and your
comments.
Following this idea we create our products and we will create the new ones! From our side, we guarantee you and we
will guarantee you also in future the best quality, the best fruits of our continuous researches and the best prices.
Our LTO CLE 8.0 is the result of many hours of listening and tests involving common people, area experts, musicians
and technicians.
The results of this effort is that you can acquire an extremely efficient and universal dynamics processor. It Contains
several new circuits design which make the unit an ultimate dynamic processor: intelligent program recognition, smart
Expander/Gate and super low distortion VCA (Voltage Controlled Amplifier).
Nothing else to add, but that we would like to thank all the people that made the LTO CLE 8.0 a reality available to
our customers, and thank our designers and all the LTO staff, people who make possible the realization of products
containing our idea of music and sound and are ready to support you, our customers, in the best way, conscious that
you are our best richness.
Thank you very much.
LTO AUDIO TEAM
2

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TABLE OF CONTENTS
1. INTRODUCTION........................................................................................................................................4
2.1 Some technical stuff
2. THE CONCEPT BEHIND..........................................................................................................................4
2.2 Voltage Controlled Amplifier (VCA)
2.3 Inputs
3. CONTROLS................................................................................................................................................6
3.1 Master Control Section
3.2 Expander / Gate Section
3.3 Compressor Section
3.4 Peak Limiter Section
4. READY TO ROLL?.................................................................................................................................10
4.1 Expander/Gate Section
4.2 Compressor Section
4.3 Peak Limiter Section
6. TECHNICAL SPECIFICATIONS .................................................................................................................................15
7. WARRANTY ...............................................................................................................................................................17
5. INSTALLATION AND CONNECTION.....................................................................................................12
5.1 Mains Connection
5.2 Audio Connection
5.3 Rack Mounting
3.5 The Rear Panel

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1. INTRODUCTION
You are now the Owner of an CLE 8.0 Compressor/Limiter/Gate. The CLE 8.0 is a very powerful dynamic processor.LTO
We have included in it several innovative circuit designs that make the CLE 8.0 a very versatile processor: smart and fast
recognition of the program, adjustable Expander/Gate and very low distortion Voltage Control Amplifier (VCA).
Feature List:
Smart Knee Control Compressor (SKC)
The AUTO Function
Smart Ratio Control expander (SRC)
Smart Gain Control peak limiter (SGC)
This function includes two important functions: Clipper and program limiter. The peak limiter will be activated
above a certain threshold that is adjusted by the User and will radically restrict signal peaks. But what about
if the threshold of the Limiter is surpassed only for a few milliseconds? SGC will turn on automatically and
reduce the output signal so that you will not hear any distortion. Smart, isn't it? The SGC proves to be very
efficient in loudspeaker protection and to reduce undesired peaks in digital situations.
2.1 Some technical stuff
Good old analog technology: It will allow us to manufacture audio equipment with a very high dynamic range:
up to 125 dB. But the dynamic range of digital equipment is more or less 25 dB less. A further reduction in dy-
namic range occurs with the use of tape recorders and/or vinyl records.
2. THE CONCEPT BEHIND
Ok,Ok, you do not want to get advantage of our AUTO function and be the Master of your own mix.
We have provided your CLE 8.0 with User Adjustable attack and release time for the best total manual control.
Attack and Release Controls:
2.1.1 It is not just Music
Yes, a piece of electronic will produce some noise. When the current flows through a conductor this will generate
a certain movement of the electrons and therefore: noise. And throughout the whole spectrum of audio. Imagine
what happens when this inherent noise will be amplified. Yes, today one can use "low-noise" components but
still such components will present a certain level of residual noise.
For example with tape recorders it will not be possible to get an S/N (signal to noise) ratio better than 70dB.
This level would not be accepted today by the increased sensitivity of the Listeners. It is possible to improve
the performance of a tape recorder: Absolutely no!
Your CLE 8.0 includes AUTO function switch on the front panel. Thanks to the AUTO function attack and release
times of the program materials are automatically analysed. Then the dynamic range of the program is heavily com-
pressed in a very musical way so that there will not be any audible breathing or pumping effect.
Soft knee or hard knee? This is the question! SKC combines both: In the "soft knee" mode you control the program
material so that the compression will be the most musical and inaudible. ON the other end, the hard knee function
is used for better precision, limiting signal peaks with precision and will allow you to add creativity to the dynamic
processing. This function also allows you to protect other equipment in the signal loop against distortion.
During music pauses or when a quiet session occurs, the noise floor maybe highly amplified and this effect may
be exaggerated because of inappropriate use of the expansion ratio. The SRC control will adjust the expansion
depending on the input signal so that those signals, which are slightly above the noise floor level, will get the major
benefits.

5
2.1.2 Introducing Audio Dynamics
Chart.1: The dynamic range capabilities of various devices
Chart.2: The interactive relationship between the operating level and the headroom
2.1.3 More technical stuff about Compressor/Limiters
Clipping Signal heavily distrortedClipping Signal heavily distrorted
Low level signal drowned out by noiseLow level signal drowned out by noise
Clipping Aera
Noise Aera
Try to measure the dynamic range of musical instruments. You will find out that your ear will handle such
range during which the distortion and overloading will be generated in your audio equipment.
To avoid these, compressor/Limiters will be used. Both Compressors and Limiters more or less do the same
job but Limiters brutally limit the audio signal above a set threshold, while Compressors handle signal in a
much more civilised way and over a wide range of levels. If an audio signal exceeds the threshold set by
the User the limiter will kill any audio signal above that threshold. Period! Also Compressors perform their
function when the audio signal exceed a certain threshold but the signal is not killed brutally. The audio signal
will be reduced in gain in proportion with the amount above the set threshold.
So the operating level must be as high as possible but not high enough to generate distortion.
Thriky uh?
There is a very easy way to obtain this. With the volume knob in hand you increase the volume during low
passages and decrease the volume during loud passages. Unfortunately even the Great Houdini would not
be fast enough to monitor carefully the speed of the musical signal and it would be impossible to detect sig-
nal peaks and consequently levelling them out. Manual control is therefore out of question. The answer is
AGC (automatic gain control); a device that will monitor the signal in real time and that will adjust the gain
for the best S/N ratio without producing distortion. So, the name of this device is "Compressor/limiter".
The human ear can detect the noise generating by falling leaves as well as the roar generated by the taking
off space shuttle. Unfortunately no analog, nor digital device can reproduce such wide spectrum. Please
look at Chart.1 and you will see the difference if dynamic capacity of various devices when compare to the
human ear. More problems occur when handling high level signals and low level signals. When you reach
the high level limit you may incur in distortion because of the dynamic range of the instrument therefore a
certain "reserve" must be maintained to avoid distortion. This reserve is known as "headroom" and it is usu-
ally set at 10-20dB. Would not be easier just to reduce the operating level? Yes it would but you would put
low level music signals at the same level of the basic noise floor so the overall quality of the signal would be
highly deteriorated. Please look at Chart.2 and note the Usable dynamic range (including headroom) versus
high level distortion generated by peaks, and Noise floor level.

6
2.1.4 More about noise: Expanders and Noise-Gates
A lot of instruments such as microphones, amplifiers, guitar pickups, etc generate some noise, either at low fre-
quencies (hum) or at high frequencies (hiss) Such noise will inevitably interfere with the quality of your audio
signal. Now, if you scream into a microphone you will not hear the noise generated by such microphone because
such noise will be "masked" by the higher level of the signal, your voice in this case.
But if you sing into your microphone more gently in a soft passage, the level of the signal generated by your
voice will get much closer to the floor noise level and such floor noise will become disturbing. In order to kill this
problem Expanders and noise-gates are used. An expander is the opposite of a compressor: attenuating the
signal when the amplitude drops they can limit the floor noise.
Now, we do not need dramatic expansion of a signal across the range, This would generate a resulting dynamic
range of over 150dB. For this reason the amplitude control will be applied only to those audio signals which
are below a set threshold. Those audio signals above the set threshold will not be affected. Noise-gate can be
regarded as a simple Expander. But the Expander will attenuate the audio signal continuously below the set
threshold while the noise-gate will simply dramatically cut-off the audio signal completely.
2.2 Voltage Controlled Amplifier (VCA)
The VCA is the soul of the CLE 8.0 and it is one of the best components available today in his category thanks to its exce-
llent performances in terms of distortion, linearity, noise and temperature stability
2.3 Inputs
2.3.1 Take it easy: Balanced Inputs
To make your life easy and clean we have provided CLE 8.0 with electronically balanced inputs. Even if you
operate at high signal levels, hum and noise will be reduce automatically. There is also a servo-function that
will automatically adjust the internal level when unbalanced connectors are detected. The correction if of 6dB
and it will avoid differences in level in between input and output signal.
3. CONTROLS
The CLE 8.0 presents with 8 channels. Each channel is equipped with the same control elements: 6 push-button switches,
8 rotary controls and 22 LEDs except channel 1 which short of the LINK CH1 push-button only.
Pic.1: Front Panel of The CLE8.0
3.1 Master Control Section
76543
1
2
Pic.2: The Master Control Section
15
-6
202530
-24 -12-18
110 6 3
+12+60 +18
GAIN REDUCTION(dB)
IN/OUT LEVEL(dB)
GAIN REDUCTION(dB)
IN/OUT LEVEL(dB)
15
-6
202530
-24 -12-18
110 6 3
+12+60 +18
SC FILTER IN/OUT METER
LINK CH1
SOFTLINK ON INTPUT
SC FILTER IN/OUT METER
SOFT INPUT
BYPASS/COMP
COMP
BYPASS/COMP
COMP
SMART
SMART
SMART
SMART SMART
SMART
SMART
SMART
SMART
SMART

5. SC Filter switch
Engaging this switch to insert a Low-cut filter in the sidechain path and thus limits the influence of low frequencies
on the CLE 8.0's control processes.
6. Smart switch
Engaging this button to switch the "Hard Knee" characteristics to SKC (Smart Knee Control). SKC provides a
compression of the program material and should therefore be used whenever compression should be more or
less inaudible.
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1. Gain Reduction Meter
It indicated the gain reduction. The range displayed is 1 to 30 dB.
2. Input / Output Level Meter
It will read the actual Input or Output Level. The range goes from -24dB to +18dB.
3. Bypass Switch
This switch simply turns off the correspondent channel. It can also be used to make an A/B comparison in between
processed and unprocessed signal.
4. Input / Output Meter Switch
7. Link CH 1 switch
Every channel contains the Link CH1 switch except the CH1. Activating this switch will link the corresponding
channel to CH1, and the CH1 will take control of the corresponding channel.
3.2 Expander / Gate Section
Pic.3: Expander/Gate Section
10
89
8
1.5
1.2
7
2.5
0
EXP/GATE(dB)
45
OFF +15
RATIO(1:N)
9. Ratio Control
This control determines the expansion ratio when the signal drops below the threshold level. The expansion ratio can
be set from 1:1.2 to 1:8 (Low ratio for Expander application or 1:8 for Gate application).
10. Threshold LED
The "+" Led lights up when an audio signal is below the set threshold. The "-" Led lights up in presence of an
expansion
8. EXP/GATE control
This control adjust the threshold level for the Expander / Gate Section in the range of Off to +15dBu. Signals
below this level cause expansion.
When the switch is ON the level indicator will read the input level. When it is OFF the level indicator will read
the output level.

3.3 Compressor Section
8
Pic.4: Compressor Section
11 13 14
12
1516 17
150
6
1
7015
30
0.1
0.05
0.3
3
5
1.5
0.5
-10
+20-20
0
+10
COMPRESSOR(dB) RATIO(N:1)
AUTO
ATTACK(mSec) RELEASE(dB/Sec) OUTPUT GAIN(dB)
-30
-40
+10
+20 1
210
4
1
11. Compressor Control
This control adjusts the threshold level for the Compressor section in the range of -40dB to +20dB. The SKC
(Smart Knee Control) is applied to the audio signal, which is a maximum of 10dB above the set threshold. Above
such level (10dB) a hard knee compression will be applied.
12. Compressor LED
These LED's will show you the state of the input signal in relation to the threshold level. If the input signal
falls below the set threshold level, the left "-" LED will light up. This means that no signal is being compressed.
When the input signal reach the set threshold level, the middle LED lights up. This means the compression
function hasn't been activated. If the input signal rises above the set threshold level, this signal will be com-
pressed and the "+" LED lights up.
13. Ratio Control
The ratio between the input and output level of audio signals exceeding the set threshold level is determined by this
control. This control is manually adjustable from 1:1 to :1.
14. Attack Control
This control determines how fast the compressor is to respond to audio signals that will exceed the set threshold.
It can be manually adjusted from 1 to 150 milliseconds.
15. Release Control
This control determines how fast is the compressor to return to unity gain when the audio signal falls below the set
threshold level. It can be manually adjusted from 0.05 to 5 seconds.
16. Auto Switch
Who needs Attack and release control? Activate this switch and these controls will be deactivated. Attack and release
controls will be automatically set by the unit depending on the program material.
17. Output Gain Control
Through this control you can vary the output signal by a maximum of 20 dB. In this way you can recover a level
that had been lost because of the compression process.
3.4 Peak Limiter Section
Pic.5: Peak Limiter Section
19
18
+4
0
+18
OFF
PEAK LIMITER

3.5 The Rear Panel
9
Pic.6: Pear Panel Of The CLE8.0
OUTPUT OUTPUT OUTPUT OUTPUTOUTPUTOUTPUTOUTPUT
OPERATING LEVEL
RETURN SEND
4dBu
10dBV
INPUT
OPERATING LEVEL
RETURN SEND
4dBu
10dBV
INPUT
OPERATING LEVEL
RETURN SEND
4dBu
10dBV
INPUT
OPERATING LEVEL
RETURN SEND
4dBu
10dBV
INPUT
OPERATING LEVEL
RETURN SEND
4dBu
10dBV
INPUT
OPERATING LEVEL
RETURN SEND
4dBu
10dBV
INPUT
OPERATING LEVEL
RETURN SEND
4dBu
10dBV
INPUT
OPERATING LEVEL
RETURN SEND
4dBu
10dBV
INPUT
OUTPUT
CHANNEL 1CHANNEL 2CHANNEL 3CHANNEL 4CHANNEL 5CHANNEL 6CHANNEL 7CHANNEL 8
AC INPUT
EUROPE
210-240V 50Hz
RATED POWER CONSUMPTION: 40W
Fuse:T315mAL
Apparaten skall anslutas till
Jordat uttag nar den ansluts
Till ett natverk
21
3
21
3
21
3
21
3
21
3
21
3
21
3
21
3
20
21
22 25 2423
Use only with a 250V fuse
Use only with a 250V fuse
Use only with a 250V fuse
USA / Canada
100-120V 60Hz
Fuse:T630mAL
UK / Aust
240V 50Hz
Fuse:T315mAL
18. Peak Limiter Control
The threshold level of the Peak Limiter is adjusted by this control.
19. Peak Limiter LED
This Led will light up when the Limiter function is activated.
These connectors are used to input the signal source. You can input the signal via the balanced 1/4" TRS phone jack
or XLR connector.
21. Audio In
20. AC Inlet and Fuse Holder
This connector is used to connect the supplied power cord. Please check the Voltage accepted by the unit and the
Voltage available from your AC sockets before connecting the unit to the Mains.
22. Audio Out
These connectors are used to output the signal. You can output the signal via the balanced 1/4" TRS phone jack or
XLR connector.
This control is used to adapt this unit to either the -10dBV home recording operating level or the +4dBu professional
studio operating level.
The Input / Output Level Meter (2) is referenced automatically to the selected level, i.e. an optimum operating range
of the meter will always be ensured.
23. Operating Level Control
24. Send
Through this 1/4" unbalanced jack the audio signal can be routed to an external processor for sidechain effect.
25. Return
The return signal from an external processor will be inputted through this 1/4" jack.