Hi Peter,
I'm also trying to achieve simultaneous output to 2 soundcards.The problem is, that 1 zone can only output to 1 sound device at the same time. If you want to output to 2 sound devices you 1.) have to sync both devices together (because of different audio clocks) and 2.) use some additional drivers to get this up and running.
My goal is to output a bluray PCM 7.1 channel sound via HDMI to my Auro3D receiver to upmix for 4 height channels (and only for the height channels). Simultaneously I want to output the same PCM 7.1 signal to my ASIO MADI soundcard (to do some routing, soundshaping, room correction, ....).
I'm not fully succesful yet, but I tried with some ASIO router drivers namely Jack, Asiolink and asio4all. Yesterday I managed to get it running, but I have not tested it in detail. This is a rather complicated approach and maybe there's a much easier solution. Don't know. But in short this is what I have done.
1.) Install asio4all and set it to use your HDMI output (AMD, NVIDIA HDMI Audio).
2.) Install asiolink and start ASIO. Set "pick driver" to asio4all to output to HDMI. Then route from "network in" to "ASIO driver out mix" and enable connection. This routing via network does the autosync for both soundcards. Don't enable the Multiclient in asiolink.
3.) Set JRiver to also use asiolink as output but select your ASIO soundcard (your USB DAC) as output via "pick driver". Then route the "ASIO driver out mix" to "network out" and enable connection.
Voila, that's it.
You shold now have 2 clock synced outputs at the same time! You have to deal with some extra and/or different latencie for the 2 signals but you can compensate for that.
Maybe this is all too complicated, but it was the only solution that worked for me. If you need any more assistance, let me know. Or if you find an easier solution, please let me also know.
greetings,
Stefan