There's a setting in the X32 for the channel count of the USB sound card. Set that as high as you need, then reboot the X32. Then you should see that many channels at the operating system level.
In OBS, however, it insists that *every* device, in its entirety, is a single source that follows the movie standard channel assignment, simply by the channel count alone. That is:
- Mono
- Stereo
- 2.1
- Quadraphonic (4 corners, all full-range)
- 4.1
- 5.1
- ???
- 7.1
And it insists on downmixing that channel assignment into whatever OBS itself is set for. So it mashes all of your individual mics together into a single stereo signal (if OBS is set for stereo), and THEN lets you play with that mess.
I first found that out with an XR18.
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The solution is to not use OBS for multichannel inputs. Use something else to make sense of the ACTUAL channel assignment, and either give them to OBS as separate devices, or just handle all of the audio on its own and give OBS a finished soundtrack to pass through unchanged.
But since you have a digital mixer already, you might use a spare mixbus or two to create the finished signal, with all of the processing done on that side, and then send a finished 2-track (stereo) feed to the USB card, with the 2-track setting. My church has an X32, and that's (almost) exactly what we do for the stream. (the output is not USB, as that's already going to a multitrack recorder for us, but a pair of RCA aux outs feeding
a USB line-in)
Actually, that rig uses 5 mix busses and 3 matrices, in addition to the house mix, so I can have a single de-esser on any speaking mic (send it to that mix, and have the de-esser on the mix), and I can send a copy of the finished stream audio to the hall and hearing assistance but without the room/ambience mics. Thus, the "dry" stream gets mixed onto one pair, the room goes on a different pair, and the speaking mics on another single. All 5 busses go to the stereo pair of stream matrices, and only 3 go to the hall / hearing assist matrix.
And of course there's compression all over it, at several different points in the chain (compressors following compressors, each of which has a slightly different job), to turn the live mics into something well-behaved and still sounding good for broadcast, without the listeners having to crank up their volumes to hear it. The result of all *that*, finally goes out the X32's DAC's to feed the USB ADC's at exactly full-scale as measured in OBS, with no processing at all in OBS except a low-level noise gate to handle some unbalanced analog cable noise.
