If I switch by default device in my Mac sound settings then the audio starts working but when switching back to usb device that I replugged in the audio stops working again.

"Unable to reproduce the issue on the reported chrome version 61.0.3163.100 and on the latest stable 63.0.3239.84 using mac 10.13.1 with the below mentioned steps.
1. Launched chrome
2. Navigated to https://appr.tc/
3. Made a call to another device using the unique id
4. Plugged in audio cable 
5. while the call is running plugged out the cable and plugged in again.
We observed the audio was audible properly with out any issue. 

@Reporter: Could you please check the same by creating a new profile and let us know the behavior.

Thanks! "

If I use the above steps - when I unplug the usb device the audio starts coming through my machine speakers and when I plug back in it doesn't start playing back from the usb device.

I've replicated using this website https://webrtc.github.io/samples/src/content/peerconnection/audio/ - if you start a call then unplug and replug the usb device then the audio doesn't restart. On firefox the audio does start coming through the device again once replugged in.

Thanks!

[Triage] Guido: does this ring a bell? I have some vague memory of something similar.

This may happen when output goes to a nondefault output device. I think there was a bug filed about that. Selecting a nondefault output device with setSinkId(), removing the device and then replugging the device does not cause audio to be redirected back to the nondefault device.