Two‑channel valve mic preamp with switchable 48V phantom power and continuously variable input impedance.
The variable impedance can have a significant effect on the sound of the connected microphone; in particular, many dynamic models, including passive ribbons, prefer to see a higher impedance.
The Pro MPA2 can be set up for dual‑mono, conventional stereo or M/S (Mid/Side) operation.
In this last role, channel one is used for the 'Mid' mic and channel two for the 'Sides'.
Further tonal variety is offered by the ability to run the 12AX7 valves at low or high anode voltages.
The unit is in excellent condition, with original box.
A combination of the input gain and this 20dB 'boost' can be used to drive the tube stage as hard as you feel appropriate.
A further 10dB is available via the output gain control, so there's an overall maximum gain of 70dB.
Next to the input gain control is the one that governs input impedance, which ranges from 150Ω to 2.4kΩ.
To keep the lows under control, there's a smooth, 6dB/octave low‑cut filter that can be swept from 10Hz to 200Hz.
Four illuminated buttons beneath the VU meter are used to select 'normal' or +20dB of gain, phantom power, high or normal 'plate' voltage, and polarity inversion.
A further button mounted between the channels selects the M/S decoding matrix, so that an M/S mic pair fed through the unit will produce a standard stereo signal at the output.
At the extreme right of the unit is a 'stereo' button that allows the rightmost output‑level control to function instead as a stereo balance, while the leftmost output‑level control operates as a master stereo level control.