ART Pro Audio Pro VLA II User Manual
Pro VLA II™
PROFESSIONAL TWO CHANNEL VACTROL
®
/TUBE LEVELING AMPLIFIER
USER’S GUIDE
IMPORTANT SAFETY INSTRUCTIONS – READ FIRST
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 safety and operating instructions for future reference. Heed all warnings printed here and on the equipment.
Follow the operating instructions printed in this user guide.
Do not open:
Aside from two vacuum tubes, 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 mains plug appropriate for your local mains supply as provided with the equipment. If the
provided plug does not fit into your outlet consult your service agent. Route 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 grounding 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 ventilation slots or position the unit where the air required for ventilation is impeded. If the unit is to be
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 electrical shock do not expose the unit to rain, moisture or use in damp or wet conditions. 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 to excessive heat or direct sunlight, as this could be a fire hazard. Locate the unit
away from any equipment, which produces heat such as: power supplies, power amplifiers and heaters.
Environment:
Protect from excessive dirt, dust, heat, and vibration when operating and storing. Avoid tobacco ash, drink spillage and
smoke, especially that associated with smoke machines.
Handling:
To prevent damage to the controls and cosmetics avoid rough handling and excessive vibration. Protect the controls from
damage during transit. Use adequate padding if you need to ship the unit. To avoid injury to yourself or damage to the
equipment take care when lifting, moving or carrying the unit.
Servicing:
Switch off the equipment and unplug the power cord immediately if it is exposed to moisture, spilled liquid, objects fallen
into opening, or the power cord or plug becomes 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.
This symbol, wherever it appears, This symbol, wherever it appears, alerts
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Pro VLA II
PROFESSIONAL TWO CHANNEL VACTROL®/TUBE LEVELING AMPLIFIER
IMPORTANT SAFETY INSTRUCTIONS – READ FIRST .......................................................................... 1
INTRODUCTION .................................................................................................................................... 3
INSTALLATION ..................................................................................................................................... 3
Unpacking .............................................................................................................................................................................................. 4
AC Power Hookup .................................................................................................................................................................................. 4
Analog Audio Connections ..................................................................................................................................................................... 4
FRONT PANEL CONTROLS and INDICATORS ...................................................................................... 5
Power ..................................................................................................................................................................................................... 5
Input Threshold Control .......................................................................................................................................................................... 5
Ratio Control .......................................................................................................................................................................................... 5
Output Level Control .............................................................................................................................................................................. 6
Attack Control ......................................................................................................................................................................................... 6
Release Control ...................................................................................................................................................................................... 7
Gain Reduction LED Meter ..................................................................................................................................................................... 7
Bypass Switch ........................................................................................................................................................................................ 7
VU Meter ................................................................................................................................................................................................ 7
VU Meter Source Switch ........................................................................................................................................................................ 7
LED Output Meter .................................................................................................................................................................................. 8
The Link Switch ...................................................................................................................................................................................... 8
REAR PANEL I/O ................................................................................................................................... 9
Balanced Inputs ...................................................................................................................................................................................... 9
Balanced Outputs ................................................................................................................................................................................. 10
I/O Level Switch ................................................................................................................................................................................... 10
APPLICATIONS ................................................................................................................................... 11
Compressor/ Limiter ............................................................................................................................................................................. 11
Stereo Mix and Mastering..................................................................................................................................................................... 11
Vocal and Instrument Leveling ............................................................................................................................................................. 11
WARRANTY INFORMATION ................................................................................................................ 12
SERVICE ............................................................................................................................................. 13
SPECIFICATIONS ................................................................................................................................ 14
LIST OF FIGURES
FIGURE 1 – Channel 1 Controls ............................................................................................................ 6
FIGURE 2 – LED O utput Meter and Link Switch ................................................................................... 8
FIGURE 3 – Rear Panel ....................................................................................................................... 10
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INTRODUCTION
Thank you for purchasing Applied Research and Technology’s Pro VLA II. Offering a superb level of sound
quality, the Pro VLA II
years to come. The Pro VLA II
with studio and live-sound engineers, the Pro VLA II
compressor on the market - at any price! Unlike typical compressors which use solid state feed-forward
circuitry to control level detection, the Pro VLA II
way your eye adjusts to light. Just as your eye transparently adjusts to changes in light, the Pro VLA II
adjusts to changes in signal level.
The Pro VLA II was designed and constructed with the absolute best components, assuring a lifetime of
quiet, reliable performance.
The Pro VLA II offers:
- Two channel opto-isolator (Vactrol®)/tube-based leveling amplifier
- Stereo linking of channels
- Master Volume and Balance control in Link Mode
- Hand selected 12AT7 Tubes
®
- Vactrol
- Analog Optical Isolators (AOI)
has a unique design that will enhance the sonic textures of your audio system for
is one of the f inest audio compressors available. Developed in partnership
possesses a “sound” that is not available from any other
is very musical. The nature of its operation is much like the
- Non-VCA design = transparent, classic sound
- VU metering of input and output levels
- LED metering of output level with peak-hold function
- XLR balanced inputs and outputs
- 1/4” TRS active balanced inputs and outputs
- Variable Threshold & Ratio controls
- Variable Attack and Release controls
- Variable Output Level rotary controls
- 10 segment Gain Reduction LED array
- 10Hz to 100KHz Frequency Response (+/-0.5dB)
- >100dB Dynamic Range
- Low noise (-99dBm ‘A’ weighted EIN)
- Internal power supply
- 3 year parts and labor warranty
INSTALLATION
The ART Pro VLA II may be used in a wide variety of applications and environments. In a rack-mountable,
all-steel enclosure, the unit is designed for continuous professional use. Mounting location is not critical,
however for greater performance reliability we recommend that you not place the unit on t op of power amps, or
other sources of heat and/or strong magnetic fields. T he tube circuitry needs about a minute to “ warm up” and
stabilize from a cold power up.
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Unpacking
Your Pro VLA II was packed with care at the factory. The shipping carton was designed to protect it during
initial shipment. Please retain this carton for use in transporting the Pro VLA II
rack, or in the unlikely event that you need to return your Pro VLA II
contain:
- The Pro VLA II
- The owner’s manual
- User Registration Card
for servicing. The shipping carton should
when it is not installed in a
AC Power Hookup
The Pro VLA II has an internal power supply designed to operate at 100 to 125VAC, 50 to 60Hz. Units
manufactured for use outside of the United States of America have been modified to comply with the required
electrical specifications. 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 the Pro VLA II
.
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 the Pro VLA II 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 the Pro VLA II. We recommend using only highquality cables equipped with the appropriate connectors.
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