User's Manual ACL2 PRO COMPRESSOR /LIMITER /GATE R LTO www.altoproaudio.com Version 1.
Fuse SAFETY RELATED SYMBOLS CAUTION RISK OF ELECTRIC SHOCK DO NOT OPEN This symbol, wherever used, alerts you to the presence of un-insulated and dangerous voltages within the product enclosure. These are voltages that may be sufficient to constitute the risk of electric shock or death. Protective Ground Before turning the product ON, make sure that it is connected to Ground. This is to prevent the risk of electric shock.
PREFACE Dear Customer: Thanks for choosing LTOACL2 PRO Compressor/Limter/Gate and thanks for choosing one of the results of TEAM job and researches. LTO AUDIO 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.
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. CONTROLS................................................................................................................
1. INTRODUCTION You are now the Owner of an LTO ACL2 PRO Compressor/Limiter/Gate. The ACL2 PRO is a very powerful dynamic processor. We have included in it with several innovative circuit designs that make the ACL2 PRO a very versatile processor: smart and fast recognition of the program, adjustable Expander/Gate and very low distortion Voltage Control Amplifier (VCA).
2.1.2 Introducing Audio Dynamics The human ear can detect the noise generated 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 when dynamic capacity of various devices compare to the human ear. More problems occur when handling high level signals and low level signals.
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 frequencies (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.
2. Threshold Control This control adjusts the threshold level for the Expander / Gate Section in the range of Off to +15dBu. Signals below this level cause expansion. 3. 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). 4. Threshold LED The "+" Led lights up when an audio signal is below the set threshold.
11. Output Gain Control Through this control you can vary the output signal by a maximum of 20dB. In this way you can recover the level lost during the compression process. 12. SC External Switch This switch will sever the connection between the audio input and the sidechain path. But at the same time it will also allow an external signal through the SC return jack present on the rear panel. 13.
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27. Sidechain Send Through this 1/4" unbalanced jack the audio signal can be routed to an external processor. 28. Sidechain Return The return signal of an external processor will be processed through this 1/4" jack. 4. READY TO ROLL? 4.1 Expander/Gate Section Chart. 3 Function of an expander As we told you previously in this Manual the downward expander will reduce automatically the level of the audio signal when such signal is below a set threshold.
4.2.2 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 1 dB. If you have a ratio equal to 1:1 you will get the same level of input and output signal: So, no level change.
4.2.8 Gain Reduction Meter This consists of 12 LED on the front of the ACL2 PRO. Through this Led meter you can visualise the amount of gain reduction at any given time. Chart. 6 The effect of a compressor can be expressed as the amount of gain reduction that is taking place for any given input 4.3 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. Wiring Configuration Both types of connectors available on ACL2 PRO can be wired in balanced and unbalanced modes. Please see following drawing for details: For 1/4" Phone jack + + - Tip Ring + Tip Tip Ring Sleeve Sleeve TS Type Unbalanced Sleeve TRS Type Balanced TRS Type Unbalanced For XLR connector Pin2 (+) Pin2 (+) Pin3 (-) Pin3 (-) (Linked to Pin1 manually, ) Pin1 ( ) Pin1 ( ) XLR Type Unbalanced XLR Type Balanced b.
c. Insert Points Connection In case you are using the main inserts of your mixing console and you have a single jack for SEND and RETURN, you can use an insert Y cable. Please see following drawing.
6. TECHNICAL SPECIFICATIONS AUDIO INPUT AUDIO OUTPUT Type Active balanced XLR and 1/4"JACK Impedance Balanced: 50K Ohm Operating Level +4dBu /-10dBV Maximum input level Balanced and Unbalanced: +21 dBu CMRR Type >55dB @1KHz Unbalanced: 25K Ohm Impedance XLR and 1/4" JACK Balanced: 60 Ohm Unbalanced: 30Ohm Maximum output level Bandwidth +21 dBu 20Hz to 20KHz at +0,-0.5dB 0.01% typ.1KHz, @+4dBu THD +N% 0.04% typ,1KHz, @+20dBu SC RETURN SC SEND EXPANDER/GATE SECTION IMD 0.
INDICATORS GAIN REDUCTION: 12 element LED INPUT / OUTPUT LEVEL: 8 element LED EXPANDER/GATE THRESHOLD: 2 element LED ( under"+" above"-") COMPRESSOR THRESHOLD: 3 element LED ( under"+" smart "0" above"-" ) PEAK LIMITER THRESHOLD: 1 element LED (Limiter Function ) Function switch: LED indicator for each POWER SUPPLY 95-120V POWER CONSUMPTION 14 Watts DIMENSIONS 483(W) 194.5(D) 44(H)mm (19" 7.7" 1.7") WEIGHT 3.1kg(6.
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.
SEIKAKU TECHNICAL GROUP LIMITED No. 1, Lane 17, Sec. 2, Han Shi West Road, Taichung 40151, Taiwan http://www.altoproaudio.com Tel: 886-4-22313737 email: alto@altoproaudio.com Fax: 886-4-22346757 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 c 2005 SEIKAKU GROUP NF01957-1.
