Delock 63926 Virtual 7.1 USB Soundcard as Line In

Hi! I bought this Delock Usb-Soundcard as it was the only cheap stereo line-one I could find. It is supported as a playback device, but I’d like to use its line-in only.

What I’m trying to do:

  • Output: Hifiberry Amp
  • Input: Delock

However, when I boot Volumio with both adapters connected, I can no longer play audio:

Failed to open "alsa" [alsa]; Failed to open ALSA device "hw:2,0": Device or resource busy

I tried to disable the I2C dac, reboot and enable it again, but the problem persists as long as both adapters are connected. Connecting the Delock after booting will not break playback and the line-in option appears in the sidebar, but it appears no signal is picked up.