Raspbian Bullseye - Updating alsa options

First make sure you can see the alsa card for the USB audio device with

cat /proc/asound/cards

And look for something that says "USB Audio" or similar

Depending on whether you are running a Pi 4 or other, it may be device 1, 2 or 3.

we used to recommend manually setting the device number to be your USB audio card but that turned out to be fragile because the HDMI audio device numbers would change. 

So now we suggest just disabling the built in headphone jack audio, and letting the USB audio card be 'first'

Start by disabling the built-in headphone jack with

sudo nano /etc/modprobe.d/raspi-blacklist.conf

and typing in 

blacklist snd_bcm2835

hit return, then save with Control-X then Y then Return (to save)

Then enable the USB audio card with

sudo nano /lib/modprobe.d/aliases.conf

find the line with

options snd-usb-audio index=-2

and put a # in the beginning of that line. Then exit and save file.

Then sudo reboot to 'set' the changes

Upon reboot, if you run sudo aplay -l  to list the interface, the USB audio card will be first and the default!