To list the primary audio device on the system, use the ls -l command on the /dev/audio device link. As you plug in additional USB devices, the command output identifies the device to which /dev/audio connects. This device automatically becomes the primary audio device.
For example, by default, the system's audio is the on-board audio.
$ ls -l /dev/audio lrwxrwxrwx 1 root root 7 Feb 13 08:47 /dev/audio -> sound/0
Suppose you connect a USB speaker to the system. The command output would then be as follows:
$ ls-l /dev/audio lrwxrwxrwx 1 root root 10 Feb 13 08:46 /dev/audio -> usb/audio0
If you add another audio device, such as a USB microphone, the command output would also change.
$ ls -l /dev/audio lrwxrwxrwx 1 root root 10 Feb 13 08:54 /dev/audio -> usb/audio1
To list all the USB audio devices that are connected to the system, use the same ls command on all the audio device links.
$ ls -lt /dev/audio* lrwxrwxrwx 1 root root 7 Jul 23 15:46 /dev/audio -> usb/audio0 lrwxrwxrwx 1 root root 10 Jul 23 15:46 /dev/audioctl -> usb/audioctl0/ % ls -lt /dev/sound/* lrwxrwxrwx 1 root root 74 Jul 23 15:46 /dev/sound/1 -> ../../devices/pci@1f,4000/usb@5/hub@1/device@3/sound-control@0:... lrwxrwxrwx 1 root root 77 Jul 23 15:46 /dev/sound/1ctl -> ../../devices/pci@1f,4000/usb@5/hub@1/device@3/sound-control@0:... lrwxrwxrwx 1 root other 66 Jul 23 14:21 /dev/sound/0 -> ../../devices/pci@1f,4000/ebus@1/SUNW,CS4231@14,200000:sound,audio lrwxrwxrwx 1 root other 69 Jul 23 14:21 /dev/sound/0ctl -> ../../devices/pci@1f,4000/ebus@1/SUNW,CS4231@14,200000:sound,audioctl
Note that despite the multiple audio devices, the /dev/usb/audio0 is the primary audio device.
You can also use the prtconf command to display USB device information.
$ prtconf . usb, instance #0 hub, instance #0 mouse, instance #0 keyboard, instance #1 device, instance #0 sound-control, instance #0 sound, instance #0 input, instance #0 .
To change the primary audio device to a USB audio device, plug the USB device to the system. The /dev/audio link automatically points to this device. To revert to using the on-board audio device, simply remove the USB device.