Engl E580 MIDI preamp, Egnater IE4. Not as obscure as some, but still months of digging.
I found the Engl after searching through archived Craigslists ads. The 220v versions are easier to find, but can't easily be converted to U.S. voltages. I finally found the Egnater in Sweden, and it was just a couple jumpers on the PCB to change the voltage.