I'm having the same problem with my headphones (Sennheiser 3D G4ME). These headphones can be set to 7.1 channels and then voicechat doesn't give me the "Voice Chat output" and "Voice Chat input" options (only 'default') and DCS crashes when trying to connect to a voicechat enabled server.
When setting the headphones to 2 channels I can then choose the "Voice Chat output" and "Voice Chat input" options and it works.
This is the only case where I ever had problems with the 7.1 channels - so far, all games, teamspeak, SRS, discord, and even DCS itself (other than voicechat) didn't mind...