Pro VLA II™ PROFESSIONAL TWO CHANNEL VACTROL®/TUBE LEVELING AMPLIFIER USER’S GUIDE
IMPORTANT SAFETY INSTRUCTIONS – READ FIRST This symbol, wherever it appears, alerts you to the presence of uninsulated dangerous voltage inside the enclosure. Voltage that may be sufficient to constitute a risk of shock. This symbol, wherever it appears, alerts you to important operating and maintenance instructions in the accompanying literature. Please read manual. Read instructions: Retain these safety and operating instructions for future reference.
Pro VLA II PROFESSIONAL TWO CHANNEL VACTROL®/TUBE LEVELING AMPLIFIER IMPORTANT SAFETY INSTRUCTIONS – READ FIRST .......................................................................... 1 INTRODUCTION .................................................................................................................................... 3 INSTALLATION ..................................................................................................................................... 3 Unpacking ..............
INTRODUCTION Thank you for purchasing Applied Research and Technology’s Pro VLA II. Offering a superb level of sound quality, the Pro VLA II has a unique design that will enhance the sonic textures of your audio system for years to come. The Pro VLA II is one of the finest audio compressors available.
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 when it is not installed in a rack, or in the unlikely event that you need to return your Pro VLA II for servicing.
FRONT PANEL CONTROLS and INDICATORS Power The POWER switch turns the power on and off to the unit. The Pro VLA II should be turned “on” with all monitor levels turned down to protect against any “thumping” caused by power up. Likewise, the Pro VLA II should be turned “off” after turning all monitor levels down. When the POWER switch is turned on, the VU meters will light. LEDs will light if its associated switch is in the “in” position.
FIGURE 1 – Channel 1 Controls Output Level Control The OUTPUT LEVEL control serves two functions. The CH1 knob always controls the output level of CH1, but can also serve as a “MASTER” output level when the Link Mode is active. The fully counter-clockwise position of the knob mutes the output. The CH2 OUTPUT LEVEL control operates as a standard CH2 level control or as a “BALANCE” control when the Link Mode is active.
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” artifacts2 Gain Reduction LED Meter The GAIN REDUCTION meter displays the Pro VLA II attenuation action.
FIGURE 2 – LED Output Meter and Link Switch LED Output Meter This meter displays both average and peak levels of the output signal. The LED labels indicate how far the output is away from full maximum output in dB. In each bargraph, a single LED is held on for a little over one second, displaying the peak level. Some peaks may not be audible, but can cause clipping in equipment following the Pro VLA II. Average levels are indicated by a histogram style display.
REAR PANEL I/O The Pro VLA II™ XLR connectors follow the AES standard of: Pin 1 = Ground, Pin 2 = Hot (+), Pin 3 = Cold (-). The balanced 1/4” phone jacks are typical TRS connections: Tip - Hot (+), Ring - Cold (-), Sleeve - Ground. Balanced Inputs The Pro VLA II™ provides both an XLR and 1/4” input jack. Both jacks are balanced. 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.
FIGURE 3 – Rear Panel Balanced Outputs The analog output of the Pro VLA II™ is available on both a 1/4” TRS balanced jack and an XLR jack. This output is active pseudo balanced. The output has a 100 Ohm impedance into a balanced or unbalanced load. The LED and analog VU meter monitor the level present at this output. “0” VU on the analog VU meter corresponds to +4dBu (about 1.23 Volts RMS). “0” on the LED bargraph OUTPUT LEVEL meter corresponds to an output level of +16dBu into a balanced load.
APPLICATIONS Compressor/ Limiter The main application of the Pro VLA II™ 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. Stereo Mix and Mastering Because of its low noise and excellent tonal qualities, the Pro VLA II™ is ideal for processing mixes when recording to DAT, hard disk or analog recording devices.
WARRANTY INFORMATION Limited Warranty: Applied Research and Technology will provide warranty and service for this unit in accordance with the following warrants: Applied Research and Technology, (ART) warrants to the original purchaser that this product and the components thereof will be free from defects in workmanship and materials for a period of three years from the date of purchase.
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 the ART unit is at fault, go to www.artproaudio.com.
SPECIFICATIONS Input Impedance Balanced/Unbalanced ................................................................10K Ohms Maximum Levels Range Switch .............................................................................+4dBu/-10dBV selectable Inputs .........................................................................................+20dBu (in +4dBu mode) / +10dBV (in –10dBV mode) Output.........................................................................................
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