Hi! Thank you, GlennO, for this important guide. I hope to finally acquire my Axe FX 3 within the next 3-6 months.
Alas, as y'all know, you can't just make an aggregate audio device on Windows. But you can do s.th. similar (or even the same?) using 3rd party software! And, of course, there is no affiliation; I'm just a happy user.
VB-Audio are primarily known for their useful "Voicemeeter" audio routing app. But a while ago, they introduced "VB-Audio Matrix". I'd link to it, but my post count is not high enough yet. Just google VB-Audio & Voicemeeter, you'll find their site no problem. On the website, you'll find it under "Audio Apps -> Matrix".
With this app, you can route several ASIO, WDM, WASAPI, MME & DX devices (internal or USB) into one or more virtual ASIO device(s) and/or virtual audio cables or network streams, sync it with a master devices clock (hard- or software), route the signal between different apps, and so on and so forth. Every in- and output is conveniently mappable in a matrix.
I currently route my Axe I/O's and Fantom-8's direct USB audio to a single virtual ASIO device and set that as in-/output in Live 11, routing the VASIO's (and therefore Live's) output back to my Axe I/O's monitor out. Additionally, I route WACUP's (Winamp Community Update Project) audio to the same monitor out, but not via the mentioned VASIO, but via a virtual audio cable, so Live won't record it - but I could easily map it to the VASIO so that Live
could.
Oh, and all the while, my internal sound card is set as primary audio device, handling all my other media/browser/system sound needs through my 5.1 speakers without getting in the way.
Once I get my AFX3, I'll just connect it via USB and route it into my VASIO as well.
I hope this helps and gives GlennO (and everybody else) something more to explore.