Since MacOS Sierra, I can now get my USB audio inputs working from Korg Kronos, POD HD500X and Roland TD30.
That’s on-top of my 3x RME Multifaces.
So, I have 60 inputs on an aggregate device, which are all working in Ableton.
…but on Cubase, I can’t see the POD, which is input 59 and 60 (stereo).
Does anyone know if there’s an issue which limits inputs in Cubase?
Depends on the version. Here are the limits.
Thanks, I should have mentioned:
I’m on the full 8.5 Pro, I should be OK according to that: “256 physical inputs and outputs”.
Wonder why it’s working in Ableton, but not Cubase?
Also interesting - Kronos on Cubase, via the aggregate device is producing pops and crackles (it’s set up for drift correction).
It’s fine on Ableton. 
Increasing the audio buffer size doesn’t help.
Well, Steinberg support just told me something interesting.
Aggregate devices aren’t supported by Steinberg’s DAW!
That’s the only method I have for combining my 3 RME Multifaces!