VLC Microphone Preamplifier/EQ/DI
HAZELRIGG INDUSTRIES
12
OPERATION
Input
Since the input cable will be carrying very low level audio, it is important that a well-shielded
cable is used. There should be no additional connectors, patch jacks, switches, etc. between the
microphone and the VLC input. This can be achieved with a dedicated line from an XLR
connector in the studio to each VLC in the control room. Although long input cable runs have
little effect on the performance of the VLC, it is preferable to keep the input line as short as
possible.
One successful method is to place the VLC in the studio with only a short cable to the
microphone. Line level from the VLC output is then fed back to the control room. Avoid locating
the VLC where it will be subjected to high sound levels or excessive vibration (such as on a drum
riser).
Output
The output of the VLC is line level, transformer balanced. Note that vacuum tube equipment is
more sensitive to load impedance than solid state units. The VLC design is optimized for feeding
a balanced bridging input (20k ohms or greater). When feeding a 600 ohm load, there may be a
slight degradation of some of the specifications. In modern studio equipment, bridging line inputs
are universal. If the device being fed by the VLC has an input termination switch, that switch
should be in the “off” position.
The VLC can feed balanced or unbalanced inputs with no need for any modification in output
wiring. Either pin 2 or 3 can be grounded, although pin 2 is normally used as the ”hot” and pin 3
as ground unbalanced configurations.
