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 PR
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.
OVERVIEW Design The PRO VLA (Vactrol-based Leveling Amplifier) is a multi-purpose tool for audio engineering and recording. Enclosed in a 2U (3.5” high) rack-mountable chassis are two independent channels of analog compression designed to work seamlessly with any recording, sound-reinforcement, or electronic instrument setup. A R T’s PRO VLA circuitry is a hybrid design utilizing the latest and most advanced solid state and tube technology.
track recorder, DAT machine, hard disk recorder, or analog recorder. - In a mixer’s channel insert points. - Between a microphone preamp and signal processors. - Between preamplified electronic musical instruments (synthesizers, guitars, bass, samplers, acoustic instruments with pickups) and other line level equipment. Note: the PRO VLA should be securely mounted in a standard 19” rack. SAFETY PRECAUTIONS Warning: To avoid the risk of shock or fire, do not expose this unit to moisture.
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).
equipment. Gain Reduction Meter Each channel of the PRO VLA has a ten segment LED gain reduction meter. These meters provide a visual indication of how much compression is taking place. The right-most LED in these meters is the Threshold LED. The Threshold LED will light when the input signal reaches the level set by the Threshold control. The range of the meter is -1dB to -30dB. VU Level Meter Each channel of the PRO VLA has a backlit VU meter showing either the input or output level (switch dependant).
Tube Replacement The two 12AX7A tubes in your PRO VLA have been specially selected and sorted to specific operating tolerances. The origianl tubes should provide years of trouble-free performance. 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. WARRANTY AND SERVICE INFORMATION Limited Warranty Warranty service for this unit will be provided by Applied Research & Technology, Inc.
A R T PRO VLA SPECIFICATIONS Dimensions Shipping Weight Input Connections Output Connections Input Impedance XLR, 1/4" Output Impedance XLR, 1/4" Maximum Input Level, XLR Maximum Input Level, 1/4" Maximum Output Level, XLR 19”W X 6.5”D X 3.5"H 9 Lbs balanced XLR & 1/4" TRS balanced XLR & 1/4" TRS 20K ohms, 1M ohms (unbal.) 600 ohm, 300 ohms (unbal - 600ohms bal.
