D.W. Fearn VT-3 - Manual (Page 15)

17
O P E R AT I O N
FRONT PANEL CONTROLS (see Figure 2)
Power switch (11)
Primary power is applied to the VT-3 circuits when the Power switch (11) is in
the up position. The amber pilot lamp (12) on the front panel indicates that the unit
is on. It takes about twenty seconds for the VT-3 to start working, but it is sug-
gested 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.
The GND LIFT switches connect or disconnect pin 1 of the OUTPUT connec-
tors to the unit internal ground. In most situations, the GND LIFT switch (8) will
remain in the down (pin 1 to internal ground) position. In some situations, partic-
ularly when an external instrument amplifier is connected to the AMP jack, a
ground loop may occur. This causes a hum or buzz in the recording equipment.
Placing the GND LIFT switch in the up position may help alleviate this.
HPF switch (9)
The VT-3 has a built-in high-pass filter that will smoothly roll off frequencies
below 100Hz when switched in. This may be useful in some situations where the
source has excessive bass content for the recording.
HUMS AND BUZZES
Unfortunately, it is the nature of high-impedance, unbalanced instrument output
to be highly susceptible to hum and buzz. Some of this is often unavoidable — the
instrument pickup(s) are very sensitive to the omnipresent AC fields in our envi-
ronment. Experiment with the orientation of the instrument to minimize this
source of noise. Most guitar and bass players will do this automatically, but with
keyboards it may be necessary to rotate and/or move the instrument to find the qui-
etest spot.