While transferring some Hi8 tapes, it became clear that it really needs to output just MANE L/R without an AUX file. 

That became yet another option.

To this day, it has never recorded from a digital source as originally envisioned.  The computer sources have all been copy protected news casts with crummy ENG audio, encrypted live streams with crummy live audio, or music available in file form.  It has manely recorded single ended stereo with pad set to loud.  The dynamic range has never required fine tuning a gain.

Another thing it's at the point of needing is a 3D printed board.  It could have less noise with more spacing.