Input (incl. Line setting) are transformer balanced/earth free

Microphone Input:
Gain 0dB to + 65db in 5dB steps.
(around 71dB with Lo Z button pressed)

Mic Input impedance:
around 1200 ohms normally;
or 300 ohms (with Lo Z pressed)

Output: Maximum output is >+26dBu into 600 ohms.

Output is transformer balanced and earth free

Output impedance: Around 50ohms

Freq Response: +0dB/-0.5dB 20Hz to 20kHz.

±16 vdc converted to single 24V rail inside module.
Total current draw 125mA max

Output pot: unity at CW, mute at CCW. -6dB at midpoint

Polarity flips 180 degrees when pressed in

Phantom 48V applied when in down position.

http://www.thedonclassics.com/nv73specs.html

Available as an assembled Module and as a DIY project.

No info about availability.