 https://www.kernel.org/doc/html/v4.15/sound/cards/emu10k1-jack.html
 they have 2 spdif out, so that means it should be possible to sync 2 (or 3) cards together with the spdif
 https://www.kernel.org/doc/Documentation/sound/cards/sb-live-mixer.rst
https://sourceforge.net/p/alsa/mailman/alsa-user/thread/s5hvf9hmuuo.wl%40alsa2.suse.de/

https://alsa-project.org/main/index.php/Matrix:Module-emu10k1#Audigy_2_Platinum_EX


https://www.kernel.org/doc/Documentation/sound/cards/audigy-mixer.rst

