Art MPA Gold - Phantom Switch; Phase Switch; Plate Voltage Switch

ART MPA Gold™ Microphone Preamplifier
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Phantom switch
Phantom power on the microphone input is turned on and off with this switch.
Depressing the switch will power condenser microphones and other 48volt phantom
powered devices. Phantom power is supplied to pins 2 and 3 of the input jack.
NOTE:
1) Dynamic microphones are NOT affected by Phantom power, although it should be
turned off when using dynamic microphones or line level inputs.
2) Although the 48volt phantom power ramps up and down slowly it may still create a
pop. Mute the output of the MPA Gold when engaging or disengaging phantom power to
prevent damage to equipment following the MPA Gold.
Phase switch
The Phase switch can invert the phase of the audio signal path in either channel. The
Phase switch is located after the tube circuit in the signal path, so you can hear slight
differences between different phase selections in the “normal” plate voltage mode near
saturation. There are a number of reasons why adjusting the phase is needed these
include, wiring errors and inversions in some audio equipment. Some microphones
sound different depending on the phase chosen.
If two microphones are out of phase, they may cancel at various frequencies
(depending on the distance between them). If this happens, try changing the phase of
one of the microphones and see if there is an improvement.
Plate Voltage switch
This switch sets both the tube bias point and the plate voltage level the balanced
differential tube circuit runs at. The amount of headroom is adjusted by using the Gain
switch and the input Gain control. The MPA Gold takes about 10-30 seconds to
smoothly transition from one mode to the other. There is a slight increase in gain in the
“High” plate voltage mode.
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