As I obviously appreciate listening to music, I do have two different USB DACs that I would like to use with my various Debian Gnu Linux boxes.

This turns out to be not that easy. My default music playing application used to be amarok, however the current version (in Debian Jessie) uses phonon and pulseaudio which do not detect consistently my USB DAC (this happens both with the default VLC backend, which usually detects the USB audio device but fails at using it and with the GSTreamer backend which mostly does not even detects the device). Even when it does, the result is not that great, I believe, due the reasons explained there.

Using the ALSA framework is what appears to work best but it requires a few steps.

1. Identify the device

aplay -l should give something like this:

**** List of PLAYBACK Hardware Devices ****
card 0: PCH [HDA Intel PCH], device 0: ALC269VC Analog [ALC269VC Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: PCH [HDA Intel PCH], device 3: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: Audio [Bravo-X USB Audio], device 0: USB Audio [USB Audio]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: Audio [Bravo-X USB Audio], device 1: USB Audio [USB Audio #1]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

In this example, the USB audio device is on card 1 and its identifier is hw:1. You can test that it is indeed the case, for instance with

speaker-test -t wav -c 2 -D hw:1

2. Command-line playback

export AUDIODEV=hw:1
play audiofile.flac -t alsa

Should play the audiofile FLAC file.

3. GUI player

Of course, the above is rather basic and for more elaborate players, the aforementioned article recommends guayadeque. The version in Debian Jessie has bugs when playing several FLAC files in a row and I could not really use it.

Something that works is clementine, which is a fork of an earlier version of amarok. Selecting the USB DAC is achieved by following Tools > Preferences... > Playback and replacing the default with

Output plugin: Audio sink (ALSA)
Output device: hw:1