User manual ART PRO VLA

[. . . ] PRO VLA PROFESSIONAL TWO CHANNEL VACTROL/TUBE LEVELING AMPLIFIER USER'S GUIDE TABLE OF CONTENTS Introduction Registration Features Overview Setting Up Unpacking AC Power Hookup Audio Connections Installation Safety Precautions Powering Up Front Panel Controls and Indicators Power Threshold Control Ratio Control Output Level Control VU Meter Input/Output Switch Attack Time Switch Release Time Switch Bypass Switch Stereo Link/Dual Mode Switch Gain Reduction Meter VU Level Meter Rear Panel Connections Input Output Applications Tube Replacement Warranty Information Service Information PRO VLA Specifications On-line Information 2 2 3 4 5 5 5 5 5 6 6 6 6 7 7 8 8 8 8 9 9 10 10 10 11 11 11 12 12 13 14 14 212-5004-101 1 Introduction Thank you for purchasing Applied Research and Technology's PRO VLA. Offering a superb level of sound quality, the PRO VLA has a unique design which will enhance the sonic textures of your audio system for years to come. Registration If you haven't done so already, please take the time to fill out the User Registration Card for your purchase. Having you in our data base allows us to keep you informed of updates, application notes, and new product introductions. [. . . ] Removing the chassis from its cabinet parts exposes dangerous high voltages. Caution: If your power cord becomes damaged and must be replaced, always replace it with the proper type (3 prong). POWERING UP When the power switch is turned on, the VU meters will light. LEDs will light if its associated switch is in its "in" position. Power on the PRO VLA before any monitoring levels or power amps are turned on. Like all tube-based equipment, the PRO VLA needs to warm up to operating temperature. The 12AX7 tubes will reach operating temperature within one to three minutes. During this warm up period you may experience variations due to the THD of the tubes stabilizing. This is normal and the PRO VLA will provide consistent results once this warm up period is over. If the PRO VLA 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. Then consult your dealer or A R T's Customer Service department. 6 7 Output Control The Output control sets the output gain of the PRO VLA. When the control is fully counterclockwise, the output level of the PRO VLA is attenuated by -83dB. Turning the control clockwise adds gain (sometimes called "make-up" gain). Since levels can be decreased when compression is applied, the PRO VLA has the ability to apply gain to bring the processed signal back up to unity (same as input level). To properly set the output level, adjust the Output Control while switching between Active and Bypass. When these two levels are equal in volume, the output control is set properly. VU Meter - Input/Output Switch The VU Meter Input/Output Switch toggles the VU meter between displaying either input or output signal levels. In stereo applications, place one switch in the Input position and one switch in the Output position. Note: The Zero ("0") level of the VU meter is calibrated at +4dBm when using the XLR connectors into a 600 Ohm load or - when using the 1/4" outputs into a high impedance load. Attack Time Switch The position of the Attack Time switch selects the attack characteristics for the channel of the PRO VLA. Attack Time refers to how quickly compression is added after the input signal rises above the Threshold. Since different signals have different attack characteristics, it is important for a compressor to have different settings which allow the action of the compressor to sound more natural. [. . . ] Place the PRO VLA into a channel insert, after a preamplifier, or from a direct output of a channel of a mixer. Adjust the controls of the PRO VLA to achieve the desired amount of compression. 10 11 Tube Replacement The two 12AX7A tubes in your PRO VLA have been specially selected and sorted to specific operating tolerances. In the event they need to be replaced, we reccommend replacing them with tubes available from A R T. We cannot guarantee consistent performance from "offthe-shelf" replacements. For units purchased outside the United States, service will be provided by an authorized distributor of Applied Research and Technology, Inc. SERVICE The following information is provided in the unlikely event that your unit requires service. [. . . ]