Studio Balanced Line input module / zSUM-4 expander.

zLINEIN provides two balanced 1/4" (6.35mm) line inputs, including RF filter, active servo DC suppression and zero-impedance output driver with adjustable gain (20dB max) and short-circuit protection.

http://motovilo.com/zsum-4/zlinein/

• 40 mA +12V
• 40 mA -12V
• 0 mA 5V
• 46 mm Depth

No info about availability.