MPA685 Owner’s Manual
3/2012
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7. +48V Switch
+48V phantom power can be applied to microphones requiring it by turning the +48V
switch to the up position. The +48V LED will light when the phantom power is On.
When on, +48V regulated voltage is applied to both positive and negative balanced
microphone input connections.
When turned on, +48V phantom power is supplied to the XLR as well as the ¼” audio
input jacks.
8. Phase Invert
With the Phase Invert switch in the down position, the audio signal is non-inverted at the
pre-amplifier output. With the Phase Invert switch in the up position, phase of the audio
at the pre-amplifier output is 180° relative to the input.
9. Low Frequency Response Switch
The Low Frequency Response filter applies a 6dB / octave cut to low frequencies when
activated. To activate the filter, rotate the Low Frequency Response knob clockwise to
the center or right most position.
10. Adjusting the Output Level
Use the “Output” knob to adjust the audio level so that it is compatible with the level
specifications of the tape machine, processing gear or A/D connected to the pre-amp
output.
The output buffer of the pre-amp can handle any signal level the input sections can
produce, so the increasing the Output knob to its maximum level will not degrade the
audio quality. This is true for any Input section settings, and is true for the DI or
microphone inputs.
