ART Pro VLAII Professional Two Channel Compressor

1. Introduction

The ART Pro-VLA II is a tube-driven Vactrol-based compressor/leveling amplifier designed for professional audio applications, including tracking, mixing, mastering, live sound, and broadcast situations. Its opto-electronic design, which differs from typical VCA-driven level detection circuits, allows for a more natural and musical sounding output with virtually transparent dynamic leveling, even with significant compression. The inclusion of a 12AT7 vacuum tube in the gain stage further enhances its performance, making the Pro-VLA II an ideal dynamic control device for various audio environments.

2. Safety Information

Please read and understand all safety instructions before operating the ART Pro VLAII. Failure to do so may result in electric shock, fire, or damage to the unit.

• Power Source: Connect the unit only to a 120 Volt AC power source. Ensure the power cord is not pinched or walked on.
• Ventilation: Do not block any ventilation openings. Ensure adequate airflow around the unit to prevent overheating.
• Moisture: Do not expose the unit to rain or moisture. Avoid placing objects filled with liquids, such as vases, on the unit.
• Servicing: Do not attempt to service this unit yourself. Refer all servicing to qualified service personnel.
• Tube Handling: The unit contains vacuum tubes which can become hot during operation. Exercise caution when handling or replacing tubes.

3. Setup

Proper setup is crucial for optimal performance and safety of your ART Pro VLAII. This section guides you through the physical installation and initial connections.

3.1 Physical Placement

The Pro VLAII is designed for standard 19-inch rack mounting. Ensure it is placed in a well-ventilated area, away from direct heat sources or excessive moisture. Allow sufficient space around the unit for proper airflow.

3.2 Rear Panel Connections

The rear panel of the Pro VLAII features all input and output connections for both Channel One and Channel Two. Each channel includes balanced XLR and 1/4-inch TRS inputs and outputs. An I/O Level switch allows selection between +4dBu and -10dBV operating levels to match your other audio equipment.

• Inputs: Connect your audio source (e.g., mixer output, preamplifier output) to the XLR or 1/4-inch TRS Input jacks for Channel One and Channel Two.
• Outputs: Connect the XLR or 1/4-inch TRS Output jacks to your next audio device (e.g., power amplifier, recording interface input).
• I/O Level Switch: Set this switch to +4dBu for professional studio equipment or -10dBV for consumer-level equipment. Mismatched levels can lead to noise or distortion.
• Power Inlet: Connect the supplied AC power cable to this inlet. Ensure the unit is powered off before connecting or disconnecting the power cable.

4. Operating the Pro VLAII

This section details the functions of the front panel controls and indicators, guiding you on how to effectively use the ART Pro VLAII for dynamic processing.

4.1 Front Panel Controls

• POWER Switch: Toggles the unit's power On/Off.
• INPUT THRESHOLD: Adjusts the level at which compression begins. Signals above this threshold will be compressed. Range: -30 dB to +20 dB.
• RATIO: Determines the amount of compression applied once the signal exceeds the threshold. Ratios range from 2:1 (light compression) to 20:1 (heavy compression).
• MASTER OUTPUT LEVEL: Controls the overall output level of the compressed signal. Range: -∞ to +20 dB.
• ATTACK: Sets the time it takes for the compressor to react to a signal exceeding the threshold. Range: 12 ms to 50 ms.
• RELEASE: Sets the time it takes for the compressor to return to its normal state after the signal falls below the threshold. Range: 0.3 sec to 0.6 sec.
• VU METER SOURCE (Input/Output/Bypass/Normal): Selects what the VU meter displays.
  • Input: Displays the input signal level.
  • Output: Displays the output signal level.
  • Bypass: Bypasses the compression circuit, allowing the input signal to pass through unprocessed.
  • Normal: Engages the compression circuit.
• LINK (Stereo/Dual):
  • Stereo: Links the two channels for stereo operation, ensuring consistent compression across both channels.
  • Dual: Allows independent operation of each channel.

4.2 Indicators

• VU Meters: Large, illuminated meters display the selected signal level (Input or Output) for each channel.
• GAIN REDUCTION (dB) LEDs: A series of LEDs indicate the amount of gain reduction being applied by the compressor, from -30 dB to 0 dB.
• Output Level LEDs: Green LEDs indicate output signal presence, while a red LED indicates clipping.

5. Maintenance

Regular maintenance ensures the longevity and optimal performance of your ART Pro VLAII.

• Cleaning: Use a soft, dry cloth to clean the exterior of the unit. Avoid abrasive cleaners or solvents.
• Tube Replacement: The 12AT7 vacuum tubes have a finite lifespan. If you notice a degradation in sound quality or inconsistent performance, the tubes may need replacement. This should be performed by qualified service personnel or an experienced technician. Always use high-quality replacement tubes.
• Ventilation: Periodically check that the ventilation openings are clear of dust and debris to ensure proper cooling.

6. Troubleshooting

If you encounter issues with your ART Pro VLAII, refer to the following common troubleshooting steps:

• No Sound Output:
  • Verify the unit is powered on and the power cable is securely connected.
  • Check all audio cables for proper connection and integrity.
  • Ensure the "VU METER SOURCE" switch is not set to "Bypass" if you expect processed sound.
  • Confirm input signal is present and at an appropriate level.
  • Check the MASTER OUTPUT LEVEL knob is not set to minimum.
• Distorted Sound:
  • Check the I/O Level switch on the rear panel matches your equipment's operating level (+4dBu or -10dBV).
  • Reduce the INPUT THRESHOLD or MASTER OUTPUT LEVEL to prevent clipping (indicated by red Output Level LEDs).
  • Ensure the input signal from your source is not already distorted.
• No Compression or Inconsistent Compression:
  • Ensure the "VU METER SOURCE" switch is set to "Normal" (not Bypass).
  • Adjust the INPUT THRESHOLD to ensure the input signal exceeds the threshold.
  • Verify the RATIO, ATTACK, and RELEASE controls are set appropriately for the desired compression effect.
  • If using in stereo, ensure the LINK switch is set to "Stereo" for linked compression.
• Hum or Noise:
  • Check all cable connections for proper shielding and secure fit.
  • Ensure the I/O Level switch is correctly set for your system.
  • Try isolating the unit from other electrical devices that might be causing interference.
  • If the issue persists, it may indicate a faulty tube or internal component, requiring professional servicing.

If these steps do not resolve the issue, please contact ART customer support or a qualified service technician.

7. Specifications

8. Warranty and Support

Specific warranty information for the ART Pro VLAII is typically provided with your purchase documentation or can be found on the official ART website. Please retain your proof of purchase for warranty claims.

For technical support, service, or further inquiries, please visit the ART website or contact their customer service department directly. Contact information is usually available on the manufacturer's official product page or in the packaging materials.