User Guide

acteristics for the channel of the PRO VLA. Release Time refers
to how quickly the channel returns to unity gain (no compres-
sion) after the input signal falls below the Threshold. Again,
since different signals have different decay characteristics, it is
important for a compressor to have different settings which
allow the action of the compressor to sound more natural. The
“out” position is the “Auto” setting. The Auto setting is an auto-
matically adjusting (sometimes called “program dependent”)
release time with a range of 100ms to 3 seconds. The “in” posi-
tion is the “Fast” setting. This setting has a fixed release time of
300ms. The Fast setting is ideal for punchy, repetitive signals.
Use the “auto” setting when the signal has varying characteris-
tics (long decaying notes alternating with quick notes, mix
material, etc.).
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A Bypass switch is included on each channel of the PRO VLA to
enable you to remove the unit from your signal chain. When set
to its “in” position, the channel of the PRO VLA allows signal to
pass from the input jacks to the output jacks with no process-
ing. The LED will illuminate to inform you the channel is
bypassed. In its “out” position, the PRO VLA is active and the
input signal is processed. Use the Bypass switch when setting
the PRO VLA’s Output Level to achieve unity (no boost or cut)
gain. Unity gain is achieved when the active level is the same as
the bypassed level.
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The PRO VLA may be used as two independent channels of
compression/limiting or as a stereo processor. When the Stereo
Link/Dual Mode switch is in its “out” position, the PRO VLA
operates as two independent channels. With the switch in its
“in” position, the PRO VLA is a stereo unit. In this Linked mode
the Threshold, Ratio, Attack and Release controls of channel #1
are used to control both channels of the PRO VLA. You’ll notice
these controls on channel #2 are inactive when the Stereo
Link/Dual Mode switch is “in”. This design is common among
professional compressors. It ensures that each channel of the
stereo input signal is processed identically to prevent any shift-
ing or distortion of the stereo image. The Output controls
remain independent in the Link Mode to allow for level match-
ing. The LED will light when the switch is in the “in” (linked)
position.
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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.
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The VU Meter Input/Output Switch toggles the VU meter
between displaying either input or output signal levels. The
Input setting is the signal entering into the PRO VLA. The
Output setting is the signal (post-process) leaving the PRO VLA.
In stereo applications, place one switch in the Input position
and one switch in the Output position. This enables you to see
both levels at a single glance of the meters.
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.
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The position of the Attack Time switch selects the attack charac-
teristics 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. The “out” position is the “Auto” setting.
The Auto setting is a program dependant attack time with 20ms
being the slowest the PRO VLA will take to achieve 20dB of
compression. In other words, the Attack Time circuitry in the
PRO VLA is designed to “adapt” to the signal characteristics of
the signal you are processing. The “in” position is the “Fast”
setting. This setting has a fixed attack time of 2ms. The Fast set-
ting is ideal for punchy, repetitive signals.
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The position of the Release Time switch selects the release char-
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