I have a ULN-2 with a 3d upgrade. I've found that getting OBS working with the ability to mix in mic inputs with other audio sources takes some doing on the Mac; I think this is regardless of the audio interface, not just the Metric Halo interfaces.
What I've done is:
1. Install
Soundflower
(important: You'll need to jump through security hoops to
get it installed on Mojave. I also needed to drop the master Input and Output levels of the Soundflower channels to 0 then back to max in AudioMIDI Setup, as described in
this post).
2. Install
LadioCast from the MacAppStore to be able to mix audio from apps and the MHLink input.
3. Configure LadioCast as follows:
INPUTS:
- Input 1: Soundflower 64ch - will take all audio from the system and allows you to set the level relative to the other inputs. Make sure this is routed to all outputs.
- Input 2: MHLink Audio - will take Mix 1&2 from the ULN and mix it with the other sources. If using a single channel (e.g. a mono mic), specify that channel (1 or 2) for both L and R. Make sure this is not routed to the ULN2 or Headphone output.
OUTPUTS:
- Main Output: Soundflower 2ch - This represents the mixed output, and is what we'll be recording/streaming in OBS.
- Aux Output 1: MHLink Audio - For monitoring via the ULN2.
Here's a screenshot of my configuration. Note that I also set up a third input/output pair for my gaming headset, in case I didn't want to use the full MIO setup for a quick streaming session.
If you want to get fancy and mix levels of or reroute the audio output of individual apps, an app like
SoundSource can do that (it would act as a sort of "pre-mixer" for LadioCast).
4. Configure OBS Audio
Since I was combining audio sources using LadioCast and Soundflower, I only needed a single audio input configured in OBS. I set the Mic input to be "Soundflower (2ch)", the mixture of all 3 inputs (system, mic, headset).
Now, when you're ready to stream, in System Preferences > Sound you set Output to "Soundflower (64ch)". OBS should then ingest the mixed system & MIO audio input via LadioCast, using Soundflower as a springboard.
You might also be able to get something put together using a tool like AudioHijack, but the above solution is free and still works with Mojave and my ULN-2.
I'm still in the process of getting Skype NDI audio worked out, which may introduce some new wrinkles; at some point I'll perhaps consider writing this up as a Resource. For the moment, this works to combine audio from browsers or other apps with the ULN-2's mic channel, as well as allowing monitoring of the mixed output from the ULN-2's headphone. Hope this helps.
