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SCL2™
Dual/ Stereo Compressor/ Expander/ Gate/ Limiter
USER’S GUIDE
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IMPORTANT SAFETY INSTRUCTIONS – READ FIRST
This symbol, wherever it appears, This symbol, wherever it appears, alerts
alerts you to the presence of uninsulated you to important operating and maintenance
dangerous voltage inside the enclosure. Voltage instructions in the accompanying literature.
that may be sufficient to constitute a risk of shock. Please read manual.
Read instructions:
Retain these safet y and operatin g instruct ions for future referenc e. Heed a ll warnings pr inted here a nd on the equ ipment.
Follow the operating instructions printed in this user guide.
Do not open:
There are no user serviceable parts inside. Refer any service work to qualified technical personnel only.
Power sources:
Only connect the unit to mains power of the type marked on the rear panel. The power source must provide a good
ground connection.
Power cord:
Use the power cord with sealed m ains plug appro priate f or your local m ains supply as provid ed with the equi pment. If the
provided plug does n ot fit into your outlet cons ult your service agent. Rout e the power cord so that it is not likely to be
walked on, stretched or pinched by items placed upon or against.
Grounding:
Do not defeat the groundin g and polarization means of the power cord plug. Do not remove or tamper with the ground
connection on the power cord.
Ventilation:
Do not obstruct the venti lati on slots or pos iti on the un it where t he air req uire d for ven tilat ion is im peded. If the uni t is to b e
operated in a rack, case or other furniture, ensure that it is constructed to allow adequate ventilation.
Moisture:
To reduce the risk of fire or elec trical sh ock do not expose the unit to r ain, m oisture or use in dam p or wet condit ions . Do
not place a container of liquid on it, which may spill into any openings.
Heat:
Do not locate the unit in a place close t o excessive heat or direc t sunlight, as this could be a fire hazard. Locate the u nit
away from any equipment, which produces heat such as: power supplies, power amplifiers and heaters.
Environment:
Protect from exces sive dirt, dust, heat, and vibration w hen operating and storing. Avoid to bacco ash, drink spillage and
smoke, especially that associated with smoke machines.
Handling:
To prevent damage to the controls and cos m etics avo id rough handl ing an d exce ss ive vibrati on. Pr otect the controls f rom
damage during transit. Us e adequate padding if you need to ship the unit. To avoid injur y to yourself or damage to the
equipment take care when lifting, moving or carrying the unit.
Servicing:
Switch off the equipm ent and unplug the power cord immediatel y if it is exposed to m oisture, spilled liquid, objects fallen
into opening, or the power cord or plug becom es damaged during a lightning storm or if smoke odor or noise is noted.
Refer servicing to qualified technical personnel only.
Installation:
Install the unit in accordance with the instructions printed in the user guide.
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SCL2™
Dual/ Stereo Compressor/ E x pa nder / Ga t e/ Li mit er
IMPORTANT SAFETY INSTRUCTIONS – READ FIRST ................................................ 2
INTRODUCTION ........................................................................................................... 4
INSTALLATION ............................................................................................................ 5
Unpacking .............................................................................................................................................................................................. 5
AC Power Hookup .................................................................................................................................................................................. 5
Analog Audio Connections ..................................................................................................................................................................... 5
REAR PANEL I/O .......................................................................................................... 6
Balanced Inputs ...................................................................................................................................................................................... 6
Balanced Outputs ................................................................................................................................................................................... 6
Detector Loop ......................................................................................................................................................................................... 6
FRONT PANEL CONTROLS and INDICATORS ............................................................. 7
Power ..................................................................................................................................................................................................... 7
Bypass Switch ........................................................................................................................................................................................ 7
Threshold Control ................................................................................................................................................................................... 7
Knee switch ............................................................................................................................................................................................ 7
Ratio Control .......................................................................................................................................................................................... 7
Attack Control ......................................................................................................................................................................................... 8
Auto/ Man. Switch .................................................................................................................................................................................. 8
Release Control ...................................................................................................................................................................................... 8
Output Control ........................................................................................................................................................................................ 8
The Expander/Gate Switch ..................................................................................................................................................................... 9
The Expander/Gate Threshold Control ................................................................................................................................................... 9
Compressor Attenuation LED Meter ....................................................................................................................................................... 9
Output Level LED Meter ......................................................................................................................................................................... 9
The Link Switch ...................................................................................................................................................................................... 9
APPLICATIONS .......................................................................................................... 10
Compressor/ Limiter ............................................................................................................................................................................. 10
Stereo Mix and Mastering..................................................................................................................................................................... 10
Vocal and Instrument Leveling ............................................................................................................................................................. 10
Ducking ................................................................................................................................................................................................ 10
WARRANTY INFORMATION ....................................................................................... 11
SERVICE ..................................................................................................................... 12
SPECIFICATIONS ....................................................................................................... 13
LIST OF FIGURES
FIGURE 1 – Rear Panel .......................................................................................................................................................... 6
FIGURE 2 – Channel 1 Controls
............................................................................................................................................. 8
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INTRODUCTION
Thanks for purchasing Appl i ed Resear ch and Technology’s SCL2™ Offering a superb level of sound
quality, SCL2™ has a unique design that will enhance the sonic textures of your audio system for
years to come. Developed in partnership with studio and live-sound engineers, the SCL2™ is very
musical.
The SCL2™ was designed and constructed with high quality components, assuring a lifetime of
quiet, reliable perfor ma nc e.
SCL2™ offers:
- Two channels of dynamics processing
- Selectable stereo linking of channels
- Master volume and balance control in Link M ode
- LED metering of output level
- XLR balanced inputs and outputs
- 1/4” TRS active balanced inputs and outputs
- Variable Threshold & Rati o cont rol s
- Hard/ Soft Knee selection
- Variable Attack and Release controls
- Selectable Auto attack/ release mode
- Variable output level rotary controls
- Noise reduction is selectable between Expander and Gate
- Hardwire bypass
- 8-segment Gain Reduction LED array
- 10Hz to 100kHz frequency response (+/-0.5dB)
- Internal power supply
- 3-year parts and labor warranty
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INSTALLATION
The ART
mountable, all-steel enclosure, the unit is designed for continuous professional use. Mounting location is not
critical. However for greater performance and reliability, we recomm end that users not place the unit on t op of
power amps, or other sources of heat and/or strong magnetic fields.
SCL2™ may be used in a wide variety of applications and environments. Housed in a rack-
Unpacking
The SCL2™ was packed with care at t he factory. The shipping carton was designed to protect it during initial
shipment. Please retain this carton for use in transporting SCL2™ when it is not installed in a rack, or in the
unlikely event that the SCL2™ requires servicing. The shipping carton should contain:
-
SCL2™
- The user's guide
- Power cord
AC Power Hookup
SCL2™ has an internal power supply designed to operate at 105 to 125VAC, 50 to 60Hz. Units
manufactured for use outside of the United States have been modified to comply with the required electrical
specifications for the country of use. Under no circumstances should the power cable be altered. If the cable
becomes cut or damaged, discontinue its use and have it replaced before operating
SCL2™.
The power source must provide a good ground connection, and the ground pin on the mains plug should
never be defeated.
Analog Audio Connections
Audio connections to and from SCL2™ are:
Balanced input: [XLR] Pin 2 = Hot (+), Pin 3 = Cold (-), Pin 1 = Ground
[1/4”] Tip = Hot (+ ), Ring = Cold (-), Sleeve = Ground
Balanced output: [XLR] Pin 2 = Hot (+), Pin 3 = Cold (-), Pin 1 = Ground
[1/4”] Tip = Hot (+), Ring = Cold (-), Sleeve = Ground
Unbalanced 1/4” cables may be used with no damage to SCL2™, however, we strongly recommend users
use a balanced connection whenever possible to r educe noise. W e recommend using only high-quality cables
equipped with the appropriate connectors.
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FIGURE 1 – Rear Panel
REAR PANEL I/O
Balanced Inputs
The SCL2™ provides both an XLR and 1/4” input jack. These jacks are balanced, but the 1/ 4” jack can be
used with unbalanced signals by simply plugging in an unbalanced cable.
The inputs are designed for use with line level signals ranging from –30dBm to +20dBm. While it is possible
to plug an instrument directly into the SCL2™, it is desirable to run the instrument into a preamp ahead of the
unit. This will provide a stronger signal and will keep noise to a minimum. Microphones must connect through a
microphone preamplifier (like the ART Pro MPA II) before connecting into the SCL2™.
NOTE: The SCL2™ has a passive (hardwire) bypass. This means that the bypass works even if the power is
off.
Balanced Outputs
The analog output of the SCL2™ is available on both a 1/4” TRS balanced jack and an XLR jack. This output
is impedance balanced. The out put has a 100 Ohm impedance into an unbalanced load or 200 Ohms into a
balanced load.
The LED meter monitors the level present at this output. “0” on the output meter corresponds 0dBu (.775
VRMS) at the output jacks.
Detector Loop
The Detector loop is an insert point between the buffered input signal and the Detector of the compressor.
Connecting an EQ to process this signal can contour the compressor's response to perform de-essing by
boosting 5kHz-8kHz information. Connect an audio signal to the Detect or Loop Input and have the
reduce gain when a signal is present to provide Ducking (see the APPLICATIONS section for more
information).
SCL2™
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FRONT PANEL CO NTROLS and INDICATORS
Power
The POWER switch turns the power on and off to the unit. The SCL2™ should be turned “on” with all monitor
levels turned down to protect against any thumping caused by power up. Likewise, the SCL2™ should be
turned off only after turning all monitor levels down. Power on the SCL2™ before any monitoring outputs or
power amps are turned on.
If the SCL2™ fails to power up when the POWER switch is turned on, check to see that its power cord is
plugged into an active outlet. If the unit still fails to operate properly, turn it off and unplug it. You can inspect
the fuse as long as the unit's AC power cord is unplugged. Consult an ART dealer or the ART Customer
Service Department if the fuse continues to blow.
Bypass Switch
The SCL2™ BYPASS switch physically connects the input jack to the output jack on each respective channel
(also known as a hardwire bypass). The switch is lit when the unit is bypassed and the unit's power is on. The
analog signal still passes from input to output if the Bypass switch is depressed even when power is off.
Threshold Control
The THRESHOLD control sets the point at which the SCL2™ will act on a signal. Turning this control
counter-clockwise lowers the threshold (adding more compression to a signal). Turning this control clockwise
raises the threshold.
Proper setting of the INPUT THRESHOLD control is dependent on the input signal. The easiest way to set
this control is to start with the control fully clockwise. Slowly turn the control counter-clockwise (lowering the
threshold) until the yellow (0) LED light on the COMPRESSOR ATTENUATIO N meter begins to light. Next
adjust the control (either lower or higher) for the desired amount of compression. Use the attenuation meter as
a visual guide to the amount of compression applied.
Knee switch
This switch selects either Hard or Soft knee operation. A "Hard" knee is one where above the thres hold the
compressor applies the ratio setting immediately. "Soft" knee operation gradually increases the slope above
the threshold setting until it reaches the ratio setting. This gradual increase of slope happens over an input
range of 10dB or so and subtly applies the gain reduction until it is really needed.
Ratio Control
The RATIO Control selects the “amount” of compression applied to the input signal once that signal reaches
or exceeds the threshold. This compression amount is expressed as a ratio of input to out put. For example if a
4:1 compression ratio is chosen, for every 4dB over the threshold the input signal rises, the output level only
rises by 1dB. In this case if the input signal increased 12dB over the threshold, the output level would only rise
by 3dB. Setting the ratio to 1:1 effectively disables the compressor.
In general, compression ratios of 10:1 and greater are considered “limiting". The SCL2™ may be used as
either a compressor or a limiter with all of the following:
- Multitrack recorder, DAT machine, hard disk recorder, or analog recorder.
- In a mixer’s channel insert points.
- Between a microphone preamp and signal processors.
- Between pre-amplified electronic musical instruments (synthesizers, guitars, bass, samplers, acoustic
instruments with pickups) and other line-level equipment.
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FIGURE 2 – Channel 1 Controls
Attack Control
The ATTACK control sets the time it takes the Compressor/Limiter to respond to increases in signal level (by
reducing gain) and shape the front end of the dynamics envelope.
One example is to listen to a snare hit and adjust the ATTACK control. A short attack makes the snare sound
“thin”. As the attack time goes longer (the knob is turned clockwise) more of the thump in the compressed
snare can be heard. The downside is that this creates an overshoot, or “transient”, the length of which is the
time set by the ATTACK control.
Overshoots less than 1 mSec. are very hard to hear even when they are clipped. If the ATTACK is set too
fast, the gain may be reduced too much and thereby create a pumping sound
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Auto/ Man. Switch
The attack and release control settings are applied when this switch is in the Manual mode. The Auto mode
changes the operation of the detector to apply an optimized attack and release that cannot be achieved with
manual control over attack and release. The ATTACK and RELEASE controls have no effect when in the Auto
mode.
Release Control
The RELEASE control sets the time the Compressor/Limiter takes to increase the gain after the input level
drops.
Longer settings maintain the dynamics of the input signal, while shorter settings reduce the dynamics.
Shorter settings will also increase the apparent reverberation, and at extreme gain reduction settings, lead to
breathing artifacts
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Output Control
The OUTPUT control serves two functions.
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“Pumping” in a Compressor/Limiter sounds like the signal is attenuated when it shouldn’t be.
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“Breathing” is the sound of the Compressor/Limiter turning up the gain so quickly breathing noises between words during
vocal processing are heard.
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The Channel 1 knob always controls the output level of Channel 1, but can also serve as a master output
level when the Link Mode is active.
The Channel 2 LEVEL control operates as a standard Channel 2 level control in Dual mode or as a balance
control when Link Mode is active. In Link Mode when the BALANCE control is turned f ully counter-clockwise
the Channel 1 output is fully on and Channel 2 output is muted 20dB. When centered, both channels have
equal gain. When turned fully clockwise the Channel 2 output is fully on and Channel 1 output is muted 20dB.
The Expander/Gate Switch
The Expander/Gate switch selects the slope of the noise reduction section. T he out position of the switch
selects the gate mode. This quickly acts to either pass or attenuate the audio signal to reduce the background
or system noise.
Depressing the switch selects the expander mode, providing a smooth application of noise reduction below
the selected threshold. This mode works best with instruments that you to need hear fade off gradually.
The Expander/Gate Threshold Control
The Expander/gate Threshold control adjusts the input level below which noise reduction takes place. This
control is adjusted in conjunction with the yellow Gate Threshold LED adjacent to the Output Meter. The LED
lights when there is at least 0.5dB of output attenuation in expander mode or the gate is attenuating the output
in gate mode.
Compressor Attenuation LED Meter
The attenuation meter displays the SCL2™ compressor/limiter action. The meter covers a very large range
while offering high resolution. The yellow (0) LED illuminates when the input signal reaches or exceeds the
compressor detector threshold setting (Threshold control) and results in a reduction of 0.5dB or more.
Output Level LED Meter
This meter displays the signal level present at the output of the unit. "0" on the meter corres ponds to 0dBu
(.775 VRMS) at the output jacks.
The Link Switch
The two channels of the SCL2™ can be configured for ster eo operation by depressing the LINK switch. Link
Mode connects the gain reduction of the two channels together for stereo operation. The Detector signals of
the two channels are summed so either channel's signal can trigger gain reduction. Channel 1's controls
(THRESHOLD, RATIO, ATTACK, RELEASE, NR THRESHOLD) become the master and Channel 2's controls
are ignored. The Channel 2 OUTPUT LEVEL control becomes an output balance control. Link Mode ensures
that each channel of the stereo input signal is processed identically to prevent any shifting or distortion of t he
stereo image.
Bypass switches remain independent in link mode.
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APPLICATIONS
Compressor/ Limiter
The main application of the SCL2™ is to control the dynamic range of an audio signal. Plug a line level (post
preamplifier or other gain stage) source into either input, and set the threshold and output controls to provide
the desired amount of compression to the input signal.
To keep the compression effects to a minimum, adjust the THRESHOLD and RATIO c ontrols such that the
Compressor Attenuation meter reads 6dB or less.
Stereo Mix and Mastering
Because of its low noise and excellent tonal qualities, the SCL2™ is ideal for processing mixes when
recording to DAT, hard disk or analog recording devices. Used as a mastering device, the SCL2™ is capable
of adding volume and impact to the overall signal level. The SCL2™ is ideal for live use as well.
Putting the unit into link mode simplifies the control usag e while maintaining the stereo image of the source
material. The knobs and switches on Channel 1 control everything but the output balance and bypass.
The SCL2™ really does a good job of controlling the peak content when setting the attack and release short
and the ratio to "Limit". Make sure not to set the Threshold too low however. Only 6-9 dB indicated on The
Compressor Attenuation meter is required to maximize the level of digital recordings.
Vocal and Instrument Leveling
The musical nature of the SCL2™ makes it ideal for use on a wide range of instruments and vocals. Place
the SCL2™ into a channel insert, after a preamplifier, or in line with the direct out put of a m ixer channel. Adj us t
the controls of the SCL2™ to achieve the desired amount of compression.
A good starting point for speech is a Ratio of 2:1 and gain reduction of 3-9dB. Apply the Gate to eliminate the
breath noises brought up by compression.
Adding sustain to instruments requires more aggressive settings for ratio (start at 4:1) and threshold. Gain
reduction in the 15dB range is not uncommon. If the noise brought up by severe compression is an issue,
apply the expander to provide a smooth tail.
Vocal processing may require tailoring of the detector response to prevent excessive sibilance. Connect a
graphic EQ to the detector loop and boost the 5-8 kHz bands 6dB or more to reduce vocal sibilance.
Ducking
One application of ducking is muting the background music whenever someone talks into a mic. Simply
connect the background music to be ducked to the audio input of the SCL2™ and connect the line level
buffered mic signal to the Detector Loop jack. Set the RATIO control to "Limit". Adjust the THRESHOLD control
for the amount of muting required when someone is talking into the mic. Set the ATTACK control to 1 to 2
mSec to guarantee the music fades off quickly. Adjust t he RELEASE control to set the t ime it takes to fade t he
music back in after there is no mic signal.
For a stereo music source, depress the LINK switch and make sure that the Channel 2 Detector Loop jack
has a shorting plug inserted or the same mic signal applied.
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WARRANTY INFOR MATION
Limited Warranty (USA only):
Applied Research and Technology will provide warranty and service for this unit in accordance with the
following warrants:
Applied Research and Technology, (A R T) warrants to the original purchaser that this product and the
years from the
components thereof will be free from defects in workmanship and materials for a period of
date of purchase. Applied Research and Technology will, without charge, repair or replace, at its option,
defective product or component parts upon prepaid delivery to the factory service department or authorized
service center, accompanied by proof of purchase date in the form of a valid sales receipt.
Exclusions:
This warranty does not apply in the event of misuse or abuse of the product or as a result of unauthorized
alterations or repairs. This warranty is void if the serial number is altered, defaced, or removed.
A R T reserves the right to make changes in design or make additions to or improvements upon this product
without any obligation to install the same on products previously manufactured.
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A R T shall not be liable for any consequential damages, including without limitation damages resulting from
loss of use. Some states do not allow limitations of incidental or consequential damages, so the above
limitation or exclusion may not apply to you. This warranty gives you specific rights and you may have other
rights, which vary from state to state.
The warrantee terms listed above are only valid within the United States of America. For units purchased
outside the United States, an authorized distributor of Applied Research and Technology will provide service.
For information on warranty and service policies outside the U.S., please contact your local distributor.
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SERVICE
The following information is provided in the unlikely event that your unit requires service.
1) Be sure that the unit is the cause of the problem. Check to make sure the unit has power, all cables are
connected correctly, and the cables themselves are in working condition. You may want to consult with your
dealer for assistance in troubleshooting or testing your particular configuration.
2) If you believe that the ART unit is at fault, go to www.artproaudio.com.
Select “Support”, then “Return Authorization Request” to request a return authorization number.
3) If you are returning the unit for service, pack the unit in its original cart on or a reasonable substitute. T he
original packaging may not be suitable as a shipping carton, so consider putting the packaged unit in another
box for shipping. Print the RA number clearly on the outside of the shipping box. Print your return shipping
address on the outside of the box.
4) Include, with your unit, a note with the RA number and your contact i nformation, including a return shipping
address (we cannot ship to a P.O. box) and a daytime phone number, and a description of the problem,
preferably attached to the top of the unit. Also include a copy of your purchase receipt
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SPECIFICATIONS
Input Impedance .................................. 10k Ohms
Output Impedance
Balanced/Unbalanced ............................ 200/100 Ohms
Maximum Levels
Inputs ..................................................... +21dBu
Output .................................................... +21dBu
Output Gain .......................................... +20dB max
Frequency Response .......................... 10Hz to 100kHz (+/- 0.5dB)
Dynamic Range ................................... >124dB (20-20kHz)
THD @ 0dBm Out: ............................... 0.05% (typical)
Equivalent Input Noise (EI N) ............... -97dBu (20-20kHz)
Attack Time ......................................... 0.25mSec. to 100mSec., variable
Release Time ....................................... 100mSec. to 3 Sec., variable
Slope .................................................... 1:1 to 20:1, variable
Dimensions .......................................... 1.75" x 19.0" x 5.9" (44.5 mm x 482.6 mm x
150mm)
Weight ................................................... 4.7 lbs. (2.1 kg.)
Power Requirements ........................... USA – 105 to 125 VAC / 60 Hz Export units
configured for country of destination.
.............................................................. 60 Watts Maximum - 10 Watts Idle
Note: 0 dBu = 0.775 V
ART maintains a policy of constant product improvement. ART reserves the right to make changes
in design, or make additions to, or improvements upon, this product without any obligation to install
same on products previously manufactured. Therefore, specifications are subject to change without
notice.
RMS
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www.artproaudio.com
E-mail: support@artproaudio.com
© 2014 Applied Research & Technology 522-5004-101
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