User`s manual

1. INTRODUCTION

You are now the Owner of an CLE 4.0 Quad Compressor/Limiter. The CLE 4.0 is a very powerful dynamicLTO 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)

The AUTO Function

Smart Gain Control peak limiter (SGC)

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. THE CONCEPT BEHIND

2.1.1 It is not just Music

2.1.2 Introducing Audio Dynamics

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.

Thanks to the AUTO function attack and release times of the program materials are automatically analysed in your

CLE 4.0 unit. 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.

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.

Yes, a piece of electronic will produce some noise. When the current flows through a conductor this will ge-

neralerate 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!

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.