I've tried 3stack-dig, 3stack-6ch and 3stack-6ch-dig. Each provided the choice if input source: Mic and Front Mic. I've tried both of them for each model. But the problem is still present:
- There is a "chucklink" during audio call, so the other person can hardly understand you;
- Videocall kills the microphone.
Ubuntu developers confirmed this bug.
I'm thinking it may have something to do with the fact that snd-hda-intel is being used by both devices. Are you using hdmi and if not can it be disabled? What profile are you using in 'Sound Preferences'?
I've managed to solve the problem with following workaround:
- replace Empathy with Skype
- delete pulseaudio (this removes some things like sound indicator)