Mitch, thanks a lot for pointing me to all the tools! I am having a bit of "family time" this weekend so didn't have the chance yet to use them but will check them out sometime this week.
rlebrette, my setup is as follows:
For JRiver's ASIO input, I use the ASIO client. For the output I go directly to the Fireface. But it also works if both is ASIO client or only the output is ASIO client. What does not work is if I select the FF directly for input and output without the ASIO client in between.
In my case I use the first channel pair of the FF for loopback (analog 1+2). I don't suppose it matters which channels you use, but in my case I used the first 2 channels to rule out any problems from that side and so far stuck with it. So: Channel offset in JRiver ASIO line in = 0
I output my Windows sound (incl. Spotify etc.) to software outputs 7+8 of the FF. I route these then to the hardware outputs 1+2 in TotalMix and activate loopback, which bring the signal to the inputs analog 1+2.
Maybe in order to narrow the problem down, you could try setting JRiver's
output to another (non-ASIO) output device, such as your internal sound card. Or you could output to the FF, but NOT using ASIO. Would it work then (i.e., only ASIO for JRiver's input)? In my case, it did, which is what pointed me to using the ASIO multi client driver in the first place.
What I have also got working now (as an alternative to the FF loopback) is a virtual audio cable. I used this one:
http://vb-audio.pagesperso-orange.fr/Cable/Note that although they write about ASIO on the website, the program can only bring non-ASIO inout to an ASIO sound card output. Where you would need it (ASIO input side) it does not offer ASIO (unless I misunderstood something). So I additionally installed ASIO4all.
So I can use this solution: Windows sound --> HiFi cable input --> HiFi cable output --> ASIO4all --> JRiver ASIO input.
In all these cases (FF and Hifi cable) I used 96/24 throughout the chain. This is how I have set my FF (in the FF settings) and this is how I configured the JRiver ASIO input.
Hope this helps. The non-mainstream solutions we are putting together here are a little capricious at times, aren't they. I did get quite a bit frustrated at times, too... Let me know if I can help you with further info.
mcwillems, many thanks for the clarification - this helps!
Have a nice Sunday everyone!