VLC Microphone Preamplifier/EQ/DI
HAZELRIGG INDUSTRIES
16
Boost and Cut (9)
The VLC contains a passive-style equalizer. The boost circuit employs an inductor in conjunction
with a capacitor to achieve the desired boost frequencies. The boost and cut pots adjust the levels
of equalization.
Frequency selection (10)
The frequencies for each boost and cut can be selected independently. In the upper position the
frequency selection is harmonically higher; in the lower position the selection is harmonically
lower.
Power switch and indicator (12 & 11)
Primary power is applied to the VLC circuits when the Power switch (12) is in the up position.
The red pilot lamp (11) indicates that the unit is on. It take about twenty seconds for the preamp
to start working, but it is suggested that you turn on the power at least five minutes prior to use.
The tubes are often noisy until all the internal elements reach a stable operating temperature.
Initial Set-Up
The VLC should be installed as detailed in the Installation section. With the outputs connected to
an appropriate destination (typically to audio recorder inputs), configure the studio to monitor the
VLC output. Apply power and wait about twenty seconds for the tube filaments to get up to
temperature. Check for hum, buzz, or other noise. For the first few minutes after a cold start it is
not unusual for the VLC to produce hiss, pops, and microphonic “clanks” as the internal elements
of the tubes expand from the heat. Correct any ground loop problems before proceeding.
The controls should be set as follows. The numbers refer to Figure 2 on page 14.
• Power(12).........................On
• Input Selector(2).............MIC
• Gain(1).............................Mid-point
• POL(6).............................Normal
• EQ In(7)..........................Down
• +48 (4)..............................as required for mic
