Aggregate issue: Audio not coming through when multiple interfaces connected

[MvdWal]

Hi, I just can't seem to get this to work or to figure out why I'm running into this issue...

I'm using Pro Tools 2020 on a MacBook Pro to process audio for live broadcast (for a church service). Audio is coming in from the mixer (Soundcraft Si Expression 2) via USB (have the Si Option card "MADI USB Combo Card" installed). I'm wanting to monitor and send out the final mix via a Focusrite Scarlett 8i6 3rd Gen Audio Interface, also connected via USB. I have the interface and the mixer set up in the aggregate, and all of the right channels are showing there, inputs and outputs all enabled, showing as active. Also have the aggregate selected in Pro Tools under hardware, and in the I/O configuration panel have everything showing up as expected, correctly configured, everything enabled, and outputs set to the Focusrite interface.

Here's the bit I can't work out: When I have just the Focusrite interface connected it works fine and I can get an output from Pro Tools to the interface (still via the aggregate) without an issue. However, as soon as the Mixer is also connected, I just have nothing coming into the interface. I've checked and tried all of the settings in the interface's control panel, checked the routing, but there's nothing coming into any of the inputs, while I should be getting something in one of the DAW inputs in the control panel.

I know that the interface is otherwise working fine, since the workaround we've been using for the interim is to set the output to the mixer, and send that via XLR from the mixer to physical inputs on the Focusrite interface (still connected to the same MacBook) so that we can at least monitor and send an output to our ATEM switcher. But this, aside from being a pain and incredibly unwieldy, also means that we're routing the audio far too many times and have too many points at which something can be messed with or where we could be losing quality, so I really need to get the output working straight from Pro Tools to the interface.

Anyone experienced anything similar and found fixes? Or any theories? Suggestions?

Any help would be much appreciated!

[Top Jimmy]

If you are just moving the main mix from the console into Pro Tools, a more elegant solution would be to use an AES to SPDIF balun and go in the SPDIF jack on the 8i6. Frankly, aggregating is fraught with issues and is not a solution If you want something that “just works”. And as far as “just works” goes, there’s absolutely nothing wrong with passing analog between the console and the interface. You gotta look at it from a genuine production standpoint. If there’s nothing wrong with the end result, there’s nothing wrong with the method taken to get there.

[Darryl Ramm]

Yep. Aggregate is usually more of an unreliable PITA than it is worth. And not just because of what you are seeing.

The behavior you are seeing is likely things working as expected. Pro Tools does not track IO assignments by name. All that IO naming is an illusion there to entertain us simians behind the console. So when you change a Playback Engine the IO path assignments you see might change... but Pro Tools does not know to magically remap thing just because the names moved. If you want to do this and make it easier for yourself need to make sure the device you are using most of the time is first in the aggregate IO device. Then at least those IO are not moving/being disconnected.