ART Pro Audio Digital MPA-II - Two Ch. Mic Pre w/ A/D Conversion - Manual (Page 9)

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In the “Normal” (OUT) position, the tube distortion gradually rises until it smoothly clips. The tube is
run almost completely open-loop in this mode, providing a musical tube “crunch” when overdriven
with a natural recovery from clipping. The tube section can be more easily overdriven when the gain
switch is in. This mode brings out the harmonics in the input sources, particularly stringed instru-
ments.
The tube circuit runs extremely clean in the “High” (IN) position of the plate voltage switch. As signal
levels rise distortion remains very low until within 6dB of clipping, where the overload characteristics
smoothly limit the signal swing. There is increased bandwidth (>100KHz), and headroom in this mode
as well.
Mid/Side switch
The Mid/Side switch is used to decode Left/Right information when using two mics aligned for stereo
recording.
You can use either two figure-eight pattern mics or one omni-directional and one Figure-eight mic.
Analog Output control
The output signal level at the rear output jacks is adjusted by this control. It can provide from +10dB
of gain (fully clockwise) to completely muted. You can see the effects of this adjustment reflected in
the analog meters.
STEREO/Dual switch
The STEREO/Dual switch selects the operation of the output control knobs. Stereo mode gains and
operation are marked with reversed out text.
In Stereo mode, CH1 output adjusts the output gain of both channels and CH2 output control acts as
a power summed Balance control. There is a slight drop in output level in stereo mode when the
Balance knob is centered vs. at one extreme or another.