±12V protection for MIDI input

In the linked question, the 220 Ω resistors were replaced with current sources and reverse voltage protection diodes. The same can be done here:

R6 is smaller because there is less voltage in which to get enough base current for Q5 to (almost) saturate.

This circuit has no ESD protection (the antiparallel diode in the original circuit); it might be advisable to add a bidirectional TVS diode.