D.W. Fearn VT-12, Руководство по эксплуатации, Страница: 23 / 37

D.W. FEARN
VT-12 Microphone Preamplifer
26
Vacuum tube condenser mics, dynamic microphones, and ribbon mics do not require this
power and the +48 switch (1) should be turned off when using non-phantom powered mics.
Some engineers feel that the performance of some dynamic mics may be subtly degraded
with the phantom power on.
The phantom powering circuit used in the VT-12 is suitable for use with all Neumann micro-
phones, AKG 12 and 48 volt microphones, B&K phantom powered mics, all Schoeps mics,
Shure SM81 and 85 mics, Crown PZM mics, and virtually all other phantom powered mics
that require any voltage between 12 and 48.
When turned off, the phantom-power resistors are completely disconnected from the circuit
in the VT-12.
Gain (3)
The Gain control (3) is between the second and third amplification stages of the VT-12. It
should be adjusted to provide the desired output level to the console or recorder.
In some situations, the Gain control can have an effect on VT-12 distortion, but at +4 dBm
output the input stages will overload before the output. If you find that you need to run the
Gain control near the bottom of its range, the input level may be too high and you might want
to experiment with the microphone pad (if it has one), the VT-12 Input switch position, or
both. Let your ears be the judge. Slight to moderate overdriving of the VT-12 often adds
“edge,” “power,” or “excitement” to the sound.
If it is necessary to operate the Gain control near the top of its range, the input level is too
low and any padding at the mic or on the VT-12 should be reduced or removed.
Phase (4)
This switch reverses the polarity of the output of the VT-12. A detailed discussion of the appli-
cation of phase reversal of individual microphones is beyond the scope of this manu al.
Even when there is only one microphone being recorded, it may be useful to try the
“Reverse” position of the Phase control. Although there is supposed to be standardization in
polarity throughout the professional audio equipment indus try, it is possible that a wiring
error or the use of vin tage equipment built before standardization may reverse the polarity in
the recording/monitoring chain. The effect of reversed absolute polarity is subtle, but signif-
icant with some sounds. If the “Reverse” position sounds better, use it.
With more than one microphone on the same sound source (or picking up leakage from
another sound source), the Phase switch may have a profound effect on the audio quality.
Whichever position sounds best is correct. A check of mo naural compatibility (by summing
the various mics) should also be performed.