Parachuting back in for a moment to say that I finally had a chance to test it and v1-dev of @stoermelder MIDI-CAT works like a treat with 14-bit mode on my Faderfox UC4.
To make this concrete using real-world knobs and scaling, plus factory settings:
With MIDI-CAT mapping the FREQ knob of Rack VCO-2, I can tune to 440.04Hz and can get an 0.17Hz change up or down (i.e. to 440.21 or 439.87). In 7-bit mode the closest I can get to A4 is 438.2Hz and the next values up and down are 460.27 (+22.07) and (417.2) (-22), which I’d describe as a flat A# and a sharp Ab, and obviously a big audible jump. To be clear, this is the interaction of VCO-2’s knob scaling and MIDI-CAT’s mapping, not anything specific to the hardware or the 14-bit protocol, but I think it’s not a bad starting benchmark.
Some quick points:
- The UC4 has endless encoders, so it should be possible to do about as well with, say, MIDI-STEP, PILE and some fancy slew and scaling to handle knob acceleration; I’ll test this. (Basically, some version of MIDI-STEP and PILE is what’s running on the UC4 firmware anyway, and the question is whether it’s polling at an increased rate and, if so, whether that makes a practical difference);
- Slew limiting is still important to avoid audible glissandi (that is, to make glissandi into portamenti) because it’s not as though the HW is outputting anything close to the 14-bit physically traversed values in between the start and end knob positions. In practice, small slew values make changes feel highly responsive and smooth to my ear.
- Because (per @stoermelder’s comment above) MIDI-CAT needs a new MSB and LSB message before updating, switching the HW to 7-bit mode without informing MIDI-CAT will, as expected, stop all updates for that CC. The workarounds above might allow auto-switching back to 7-bit using either the timeout or the eat-one method, but there’s a certain amount of “Doctor, it hurts when I do this”; “Then don’t do that!” here.
- There are a few quality of life thoughts I might have about mapping and mode changes, but I’ll move those into a separate thread once I’ve experimented a bit more.
The upshot is that high-quality 14-bit MIDI control is available in Rack V1 thanks to @stoermelder and if you’re MIDI-mapping pitch-related knobs (in particular) with MIDI-CAT and aren’t quantizing anyway you should definitely try to use 14-bit hardware unless you like randomly sharp flats and randomly flat sharps.
I will, of course, compare this to the nOb as soon as it arrives!