D.W. Fearn VT-12, Operating Instructions Manual, Page: 21 / 37

D.W. FEARN
VT-12 Microphone Preamplifer
24
The VT-12 can feed balanced or unbalanced inputs with no need for any modification in out-
put wiring. Either pin 2 or 3 can be grounded, although pin 2 is normally used as the ”hot”
and pin 3 grounded in unbalanced configurations.
CONTROLS (see Figure 2.)
Phantom 48V Power
+48 volt phantom power is available for those microphones that require it. The front panel
+48 switch activates 48 volts for phantom powered microphones. Switch the 48 volts off for
dynamic and ribbon microphones, or condenser microphones with their own power supplies
(e.g. vacuum tube condensers).
Phantom Power Enable/Disable (Rear panel switch)
Note that ribbon microphones can be damaged from the application of phantom power, par-
ticularly if there is a fault in the microphone cable or connectors. For that reason, the VT-12
has a rear-panel swith to disable the 48V supply when using ribbon mics.
When this switch is down, it is impossible to apply 48V to the microphone. In this position,
the front panel indicators next to the 48V switch will be green.
With the rear panel switch up (ENABLED), the front panel 48V switches are enabled. No
phantom power is supplied until the individual 48V switch is turned to the “ON” position.
With the rear-panel switch in the Enable position, the front panel indicator next to the 48V
switches will turn red, indicating a potentially dangerous condition for ribbon microphones.
If the rear panel switch is set to DISABLED, and the front panel 48V switch is turned on, the
front panel indicator will turn orange, indicating that the front panel switches should be
turned off for full safety.
Note that some ribbon mics (“active ribbons”) may require phantom power to operate the
electronics in the microphone. Also note that active ribbon mics have an output level much
higher than a standard ribbon mic and may require the use of the -20 pad on the VT-12 to
prevent overload.
Gain control. Adjusts the output level.
Phase switch.
Usually in the Normal position except when it is necessary to reverse the
polarity of a microphone.
Meter switch.
Turns on or off the VU meter. Normally ‘on’ except during some test pro-
cedures or when purposely over-driving the VT-12.
VU meter.
Monitors the output level of the VT-12.
Pilot lamp. Illuminates when AC power is applied and the Power switch is on.
Power switch. Controls primary AC power to the VT-12.