USB question

[Ralf Mardorf]

On Sat, 15 Sep 2018 12:48:57 +0100, Richard Kimber wrote:
>Is there some other way I can track down what I need to do to ensure
>the DAC is recognised without having to keep un-plugging and
>re-plugging the USB cable?

That's strange, if I reboot, my USB audio device is recognized without
the need to replug it.

Maybe replugging your device just changes the card number.

Run 'aplay -l' before and after replugging.

You could allocate snd_usb_audio to a fixed card number by
/etc/modprobe.d/alsa-base.conf.

$ aplay -l | grep card
card 0: HDSPMx579bcc [RME AIO_579bcc], device 0: RME AIO [RME AIO]
card 1: EWX2496 [TerraTec EWX24/96], device 0: ICE1712 multi [ICE1712 multi]
card 3: HDMI [HDA Intel HDMI], device 3: HDMI 0 [HDMI 0]
card 3: HDMI [HDA Intel HDMI], device 7: HDMI 1 [HDMI 1]
card 3: HDMI [HDA Intel HDMI], device 8: HDMI 2 [HDMI 2]
card 3: HDMI [HDA Intel HDMI], device 9: HDMI 3 [HDMI 3]
card 3: HDMI [HDA Intel HDMI], device 10: HDMI 4 [HDMI 4]
card 4: USB [Scarlett 18i20 USB], device 0: USB Audio [USB Audio]
$ cat /etc/modprobe.d/alsa-base.conf 
# ALSA module ordering
options snd slots=snd_hdspm,snd_ice1712,snd_ice1712

I don't reserve a card number for snd_usb_audio, but as you can see
card 2 is reserved for a second ice1712 card.