PREFACE
Dear Customer:
Thanks for choosing LTO CLE 4.0 Quad/Compressor/Limter 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 then 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 4.0 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 acquired an extremely efficient and universal dynamics processor. It Contains
several new circuits design which make the unit an ultimate dynamic processor: intelligent program recognition 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 4.0 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
TABLE OF CONTENTS
1. INTRODUCTION......................................................................................................................................4
2. THE CONCEPT BEHIND........................................................................................................................4
2.1 Some technical stuff
2.2 Voltage Controlled Amplifier (VCA)
2.3 Inputs
3. CONTROL ELEMENTS .........................................................................................................................6
4. READY TO ROLL?.................................................................................................................................7
4.1 Compressor Section
4.2 Peak Limiter Section
5. INSTALLATION AND CONNECTION.....................................................................................................9
......
5.1 Mains Connection
5.2 Audio Connection
5.3 Rack Mounting
6. TECHNICAL SPECIFICATIONS .................................................................................................................................11
7. WARRANTY .............................................................................................................................................................12
3
1. INTRODUCTION
You are now the Owner of an LTO CLE 4.0 Quad Compressor/Limiter. The CLE 4.0 is a very powerful dynamic processor.
We have included in it several innovative circuit designs that make the CLE 4.0 a very versatile processor: smart and
fast recognition of the program and very low distortion Voltage Control Amplifier (VCA)
Feature List:
Smart Knee Control Compressor (SKC)
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.
The AUTO Function
Your CLE 4.0 includes and 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 compressed in a very
musical way so that there will not be any audible breathing or pumping effect.
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. THE CONCEPT BEHIND
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
dynamic range occurs with the use of tape recorders and/or vinyl records.
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!
2.1.2 Introducing Audio Dynamics
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 usually set at 10-20 dB. 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.
4
Chart. 1 The dynamic range capabilities of various devices
Clipping Aera
Clipping Signal heavily distrorted
Noise Aera
Low level signal drowned out by noise
Chart. 2 The interactive relationship between the operating level and the headroom
So the operating level must be as high as possible but not high enough to generate distortion.
Tricky 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 signal 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".
2.1.3 More technical stuff about Compressor/Limiters
Try to measure the dynamic range of musical instruments. You will find out that your ear will handle such range.
Your audio equipment will not and distortion and overloading will be generated. 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 exceed 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.
2.2 Voltage Controlled Amplifier (VCA)
The VCA is the soul of the CLE 4.0 and it is one of the best components available today in his category thanks to its
excellent 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 4.0 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.
5
3. CONTROL ELEMENTS
Your CLE 4.0 presents with four channels. Each channel is equipped with the same control elements: 3 push-button
switches, 4 rotary controls and 17 LEDs. You can operate in stereo mode via pressing the Couple switch. The details
please refer to following content.
8
7
10
GAIN REDUCTION(dB)
INPUT
/
OUTPUT LEVEL(dB)
GAIN REDUCTION(dB)
30 25 20 15 10 6
INPUT
/
OUTPUT LEVEL(dB)
12 18
GAIN REDUCTION(dB)
30 25 20 15 10 6
INPUT
/
OUTPUT LEVEL(dB)
12 18
GAIN REDUCTION(dB)
30 25 20 15 10 6
INPUT
/
OUTPUT LEVEL(dB)
12 18
30 25 20 15 10
6
3
1
24 18 12
6
0
6
12 18
LIM
12
3
1
24 18 12
6
0
6
LIM
12
3
1
24 18 12
6
0
6
LIM
12
3
1
24 18 12
6
0
6
LIM
12
10
2.5
0
10
2.5
0
10
2.5
0
10
2.5
0
CH1
CH
2
CH
3
CH
4
CLE 4.0
Quad
R
30
10
2
10
10
10
4
18
30
10
2
10
10
10
4
18
30
10
2
10
10
10
4
18
30
10
2
10
10
10
4
18
Compressor/
Limiter
ON
40
20
1
20
20
0
OFF
40
20
1
20
20
0
OFF
40
20
1
20
20
0
OFF
40
20
1
20
20
0
OFF
OFF
SMART
I/O METER
BYPASS
COUPLE
CH1 MASTER
SMART
I/O METER
BYPASS
I/O METER
BYPASS
COUPLE
CH3 MASTER
SMART
I/O METER
BYPASS
dBu
N:1
dB
dBu
dBu
N:1
dBB
OUTPUT GAIN
dBu
dBu
SMART
N:1
dB
OUTPUT GAIN
dBu
dBu
N:1
dB
OUTPUT GAIN
dBu
OUTPUT GAIN
THRESHOLD
RATIO
THRESHOLD
THRESHOLD
RATIO
THRESHOLD
THRESHOLD
RATIO
THRESHOLD
THRESHOLD
RATIO
THRESHOLD
COMPRESSOR
LIMITER
COMPRESSOR
LIMITER
COMPRESSOR
LIMITER
COMPRESSOR
LIMITER
POWER
1
5
2
6
3
4
9
11
14
12
4dBu
4dBu
4dBu
4dBu
TIP/PIN
RING/PIN
SLEEVE/PIN
2
TIP/PIN
RING/PIN
SLEEVE/PIN
2
TIP/PIN
2
TIP/PIN
RING/PIN
SLEEVE/PIN
2
1 1 0 - 1 2 0 V
3
3
RING/PIN
3
3
1
1
SLEEVE/PIN
1
1
AC INPUT
10dBV
OPERATING LEVEL
10dBV
OPERATING LEVEL
10dBV
OPERATING LEVEL
10dBV
OPERATING LEVEL
220-240V
95-120V /210-240V 60-50Hz
Rated Power Consumption
14W
FUSE:
210-240V: T315mAL 250VAC
95-120V: 630mA 250VAC
REPLACE FUSE WITH
CORRECT TYPE ONLY
OUTPUT
INPUT
OUTPUT
INPUT
OUTPUT
INPUT
OUTPUT
INPUT
CHANNEL 4
CHANNEL 3
CHANNEL 2
CHANNEL 1
13
Pic. 1
1. Threshold Control for Compressor Section
With this control you will adjust the threshold level in the Compressor. The range is varied from -40dBu to +20dBu. When
a signal exceed the set threshold by 10dB maximum the SKC will be applied, while above such level signal will be processed
with hard knee compression.
2. Ratio Control
The ratio in between input and output level signals above the set threshold is determined by this control. When the
SKC is applied such ratio is only expressed for the signals exceeding the set threshold more than 10dB. The range
of control of the ratio varies from 1:1 to :1.
3. Output Gain Control
You can increase or decrease the output signal by a maximum of 20dB. IN such a way you can recover a level lost
during the compression process.
4. Bypass Switch
Push this switch and you will deactivate the corresponding channel. You can also use the bypass switch to make an A/B
comparison in between processed and unprocessed signal.
5. Smart Switch
A hard knee compression is turned into SKC by mean of this switch. If you wish to get a compression that is quite
inaudible use the SKC mode through the Smart switch.
6. Meter Switch for input / output
When this switch is ON the Meter will read the output level. When the switch is OFF, the Meter will read the input
level.
7. Level Meter for Input / Output
You can adjust the operating level by mean of the Operating Level Switch and choose -10dBV or +4dBu. Consequently
the Meter will be the Input or Output Level with a range from -24dB to +18dB.
8. Meter for Gain Reduction
The gain reduction will be shown by this Meter with a range of 1 to 30dB.
6
9. Threshold Control for Limiter
The threshold Level for the Limiter will be adjusted by this control
10. Limiter LED
When the Limiter is active, this LED will flash up.
11. Couple Switch
When pressing this button Channel 1 and 3 will operate in stereo mode.
12. Voltage Selector and Fuse holder
Please make sure about the voltage available in your Country before connecting the unit to the AC socket. Please
consult with a qualified Engineer to change the fuse or to change the AC Voltage operation on the CLE 4.
1 1 0 - 1 2 0 V
2 2 0 - 2 4 0 V
110-120V
220-240V
THIS IS SET FOR
110V AC TO 120V
AC OPERATION
THIS IS SET FOR
220V AC TO 240V
AC OPERATION
Pic. 2
13. Audio In and Out
You can input and output the audio signal in the CLE 4.0 via XLR connectors or 1/4" jack.
14. Operating Level Control
Choose +4dBu when using CLE 4.0 in professional recording studios or -10dBV when using home recording equipment.
The Input/Output Meter will automatically self-adjust to the chosen Operating Level.
4. READY TO ROLL?
4.1 Compressor Section
Sophisticated Voltage Controlled Amplifiers (VCA) are responsible of the control of dynamics in the CLE 4.0 The operating
range of our VCA is more than 60dB. This mean that the input level or the output level can be increased or decreased in a
range of 60dB. Signals below the set threshold will not be reduced, so the dynamic control will be activated as soon as the
signal exceed the threshold level. Gain reduction will be proportioned to the amount of the signal above the set threshold
level.
4.1.1 The Threshold Control
The compressor threshold control sets the point where the input level starts to be reduced. Let's say the level
is +12dBu and the threshold control is set at +2dBu: In this case up to 10dB can be compressed. If the input
level is the same and the control is set at 10dBu the maximum compression will be 22dB, The operating range
of the threshold control is -40 to +20dBu. Turn the threshold control fully clockwise and you will get a threshold
level of +20dBu.
You must remember that the degree and the type of compression not only depend by the threshold control
but also by other controls such as Ratio, Attack and Release. .
7
4.1.2 Ratio Control
This control sets the change of input level to output level but only for the signals that exceed the threshold.
The scale of the ratio control on the front panel (calibrated in dB) indicates how much input level is required
to increase the output level by 1dB.
If you have a ratio equal to 1:1 you will get the same level of input and output signal: So, no level change.
If you have a ratio of 2:1 this means that for every 2dB increase of the input level (above threshold) you
will get an increase of output level of 1dB. ON the same way, a ratio of 10:1 means that for every 10dB
increase of the input level (above threshold) you will get an increase in output level equal to 1dB, and so on.
You need to be aware that higher ratio settings produce less natural sounds so if you wish a more minute
effect on the dynamic range of a program you should use a Ratio of 4:1 or lower.
With the SKC circuit (Smart Knee Control) you can avoid aggressive compression generated by using high
ratios. How we achieve this? Introducing a "soft knee" curve in the range of up to 10dB above the threshold
level. Hard Knee compression is then used beyond this range.
Output
Gain 0 dB
Threshold
Ratio 2:1
Ratio 4:1
Hard Knee
Limiter :1
SKA Curve
Input
Chart. 3 SKA characteristic of the compressor section
4.1.3 Output Gain Control
This Control is indispensable to compensate the loss of level at output level generated by the gain reduction caused
by the compression and limiting processing
4.1.4 Bypass Switch
This switch simply turns off the correspondent channel. This is useful to compare quickly the processed and
unprocessed signal.
4.1.5 Gain Control LED Meter
This consists of 8 LED on the front of the CLE 4.0. Through this LED Meter you can visualise the amount of gain
reduction at any given time.
Chart. 4 The effect of a compressor can be expressed as the amount
of gain reduction that is taking place for any given input
8
4.2 The Peak Limiter Section
How fast is the compressor to react to a signal which is above the threshold point? This is determined by the
attack time. A longer attack time is advisable to process low frequencies while shorter attack time is preferable
for high frequencies. IN this way you will avoid undesired dynamic distortion. But what about if you are mixing
a program with a wide range of frequencies? IN this case you should choose a setting that would benefit the
low frequency better. Well, life is not that easy for conventional compressor/limiters. Ok you handle an audio
signal made by a wide range of frequencies and you have chosen a longer attack time. But, if are using your
CLE 4.0 as a limiter the fast high frequencies will pass through untouched because the attack time is too slow
and such transients could cause distortion when the unit is connected to broadcast devices or taper recorders.
The solution in CLE 4.0 is represented by our Smart Gain Control (SGC) limiter circuit. The curve in bold is the
output signal and the dashed curve above it is the input signal. The area in between the two is the amount of
gain reduction.
The unit will activate the limiter when the signal exceeds the threshold for more than 20 microseconds. Then
1 second after that the signal is below threshold again, reduction goes back to 0dB and in this case input and
output signals are again identical.
Peak Limiting
Program Limiting
Level
Release
Threshold
Input
Output
approx. 1 s
6ms
20
15ms
t/ms
30
10
Chart. 5 SGC characteristic of the limiter section
5. INSTALLATION AND CONNECTION
5.1 Mains Connection
CLE 4.0 is provided with dual voltage plug. You must check the power supply Voltage available in your
Country before connecting the power cord in the wall outlet. Please see Page 7, paragraph 12 for further
info.
5.2 Audio Connection
The CLE 4.0 Compressor/Limiter is equipped with balanced XLR connectors as well as 1/4" phone jack and
can be connected with other units in different ways to support a vast range of applications without experiencing
a signal loss.
a. Wiring Configuration
Both types of connectors available on CLE 4.0 can be wired in balanced and unbalanced modes. Please see following
drawing for details:
For 1/4" Phone jack
+
+
+
-
Tip
Sleeve
Tip
Sleeve
Tip
Ring
Ring
Sleeve
TS Type Unbalanced
TRS Type Balanced
TRS Type Unbalanced
Pic. 3
9
For XLR connector
Pin2 (+)
Pin2 (+)
Pin3 (-)
Pin3 (-)
(Linked to Pin1 manually,
)
Pin1 (
)
Pin1 (
)
XLR Type Unbalanced
XLR Type Balanced
Pic. 4
b. In Line Connection
Please see following drawing for details.
Balanced
Tip
Ring
Tip
Ring
Sleeve
SLEEVE RING TIP
TIP RING SLEEVE
Sleeve
1
2
1
2
3
3
Tip
1
2
3
Ring
TIP RING SLEEVE
Sleeve
Unbalanced
Tip
1
2
3
Ring
Sleeve
TIP RING SLEEVE
Tip
1
2
3
Sleeve
TIP SLEEVE
1
2
3
Centre
Screen
Tip
Tip
TIP SLEEVE
SLEEVE TIP
Sleeve
Sleeve
Tip
Tip
Ring
Ring
TIP RING SLEEVE
SLEEVE RING TIP
Sleeve
Sleeve
Tip
Centre
Screen
Sleeve
TIP SLEEVE
Tip
Centre
Screen
Ring
Sleeve
TIP RING SLEEVE
1
2
1
2
3
3
Pic. 5
5.3 Rack Mounting
The most secure mounting is on a universal rack shelf available from various rack manufactures or your music
dealer. The CLE 4.0 Quad Compressor/Limiter fits into one standard 19" rack unit of space. Please allow
at least an additional 4" depth for the connectors on the rear panel. Be sure that there is enough air space
around the unit for sufficient ventilation and please do not place the CLE 4.0 Quad Compressor/Limiter on
high temperature devices such as power amplifiers etc. to avoid overheating.
10
6. TECHNICAL SPECIFICATIONS
Type
Active balanced XLR and 1/4"JACK
Impedance
AUDIO INPUT
Balanced: 50K Ohm Unbalanced: 25K Ohm
Operating Level
+4dBu /-10dBv
Maximum input level
Balanced and Unbalanced: +21 dBu
>55dB @1KHz
CMRR
Type
XLR and 1/4" JACK
Balanced: 60Ohm Unbalanced: 30Ohm
+21 dBu
Impedance
Maximum output level
Bandwidth
20Hz to 20KHz at +0,-0.5dB
0.01% typ.1KHz ,@+4dBu
0.04% typ,1KHz ,@+20dBu
0.01% typ
AUDIO OUTPUT
THD +N%
IMD
Noise
>-90dBu
Crosstalk
Type
<-100dB
Interactive Compressor
Threshold
Ratio
Variable: from -40dB to +20dB
Variable: from 1:1 to :1
COMPRESSOR
SECTION
Auto Attack Time
Auto Release Time
Output
Typ. 15ms at 10dB; 5ms at 20 dB; 3ms at 30dB
Typ. 125dB/s
Variable: from -20 to +20dB
Interactive Peak Limiter
Variable: from +4dB to OFF
:1
Type
Threshold
Ratio
PEAK LIMITER
SECTION
Stage 1:
Clipper
Attack and Release
Stage 2
zero
Program Limiter
typ. <5ms
Attack
Release
typ. 20dB/s
COUPLE
Linking CH1 (master) and CH2 CH3 (master)
and CH4; stereo operation
OPERATING LEVEL
BYPASS
Internal reference level: from +4dBu to -10dBV
Bypass switch
I/O METER
Switches input and output for the level meter
FUNCTION
SWITCHES
SMART
Enables the ` Smart Knee Control `
characteristics
Allows for frequency dependent detection
CONTOUR
GAIN REDUCTION: 8 element LED
INPUT / OUTPUT LEVEL: 8 element LED
INDICATORS
PEAK LIMITER THRESHOLD: 1 element LED (Limiter Function )
Function switch: LED indicator for each
POWER SUPPLY 95-120V /210-240V , 60-50Hz FUSE: 210-240V: T315mAL 250VAC
95-120V: 630mA 250VAC
POWER
14 Watts
CONSUMPTION
DIMENSIONS
WEIGHT
483 (W) 194.5 (D) 44 (H)mm (19" 7.7" 1.7")
3.3kg (7.27lb)
11
7. WARRANTY
1. WARRANTY REGISTRATION CARD
To obtain Warranty Service, the buyer should first fill out and return the enclosed Warranty Registration Card within
10 days of the Purchase Date.
All the information presented in this Warranty Registration Card gives the manufacturer a better understanding of
the sales status, so as to purport a more effective and efficient after-sales warranty service.
Please fill out all the information carefully and genuinely, miswriting or absence of this card will void your warranty
service.
2. RETURN NOTICE
2.1 In case of return for any warranty service, please make sure that the product is well packed in its original shipping
carton, and it can protect your unit from any other extra damage.
2.2 Please provide a copy of your sales receipt or other proof of purchase with the returned machine, and give detail
information about your return address and contact telephone number.
2.3 A brief description of the defect will be appreciated.
2.4 Please prepay all the costs involved in the return shipping, handling and insurance.
3. TERMS AND CONDITIONS
3.1 LTO warrants that this product will be free from any defects in materials and/or workmanship for a period
of 1 year from the purchase date if you have completed the Warranty Registration Card in time.
3.2 The warranty service is only available to the original consumer, who purchased this product directly from the
retail dealer, and it can not be transferred.
3.3 During the warranty service, LTO may repair or replace this product at its own option at no charge to you for
parts or for labor in accordance with the right side of this limited warranty.
3.4 This warranty does not apply to the damages to this product that occurred as the following conditions:
Instead of operating in accordance with the user's manual thoroughly, any abuse or misuse of this product.
Normal tear and wear.
The product has been altered or modified in any way.
Damage which may have been caused either directly or indirectly by another product / force / etc.
Abnormal service or repairing by anyone other than the qualified personnel or technician.
And in such cases, all the expenses will be charged to the buyer.
3.5 In no event shall LTO be liable for any incidental or consequential damages. Some states do not allow the exclu-
sion or limitation of incidental or consequential damages, so the above exclusion or limitation may not apply to you.
3.6 This warranty gives you the specific rights, and these rights are compatible with the state laws, you may also
have other statutory rights that may vary from state to state.
11
SEKAKU ELECTRON IND. CO., LTD
NO.1, LANE 17, SEC. 2, HAN SHI WEST ROAD, TAICHUNG, 401 TAIWAN
Tel:886-4-22313737
All rights reserved to ALTO. All features and content might be changed
without prior notice. Any photocopy, translation, or reproduction of part of this
manual without written permission is forbidden. Copyright 2003 Sekaku Electron
|