The primary reason I replaced my ailing Firestudio Mobile with a Studio 68c was because I could simply unplug the cables from one and replug them into the other, since the breakout cable makes for a brand-proprietary configuration. Theoretically I should have been able to go from one experience to another without a hitch. But not so much.
Stereo Playback was just fine on any pre-mixed audio from any source; but live MIDI playback from my synth (Roland Sound Canvas SC88ST Pro, with Digital Performer 11 as the DAW) was only happening in mono. After eliminating human and mechanical error on my end, I turned to Presonus for help — and it turns out, that is currently a known limitation. (And there's no reason for it and every reason to correct it. Bear with me.)
The problem is that Universal Control no longer has a mixing window. Years ago, when I first set up the Firestudio mobile, ALL playback defaulted to mono until I configured that mixing window. Once I did, stereo playback became the default. But since I no longer have access to such a window, my synth playback is frozen in mono. Because, and I quote, "When direct monitoring on the Studio 68c, the inputs will be summed together in mono. Larger interfaces like the Studio 1810c and the Studio 1824c do have software mixers in which inputs can be grouped in to stereo pairs but this is not possible on the with the Studio 68c. If you wish to monitor in stereo on the Studio 68c you will need to create a stereo track in your DAW and monitor your input from the DAW. "
This is a massive inconvenience to anyone, like me, who composes and pre-mixes instrumental audio in MIDI using hardware synth sounds, who has files going back two decades that are MIDI only, who creates separate files for digital audio work, and who uses a notation program in conjunction with the sequencer software and hardware synth.
The Studio 68c is essentially the next generation device, in every way exhibiting equivalent hardware functionality. Its software controls should be at LEAST as good, not de-featured, Please, please, PLEASE restore the mixing window to Universal Control, so that stereo monitoring is likewise restored.