How can I make my ALSA card to use the fixed number?

[rpi]

Hi,

I have the USB DAC connected to the Raspberry Pi. In .asoundrc it's defined as card 2, device 0. Sometimes after rebooting the Pi that USB DAC becomes (aplay -l) card 1, device 0 and audio doesn't go through it. Is there any way to make the USB DAC always use the fixed card number e.g. card 2?

Thanks!

 

[CharlieLaub]

You can often refer to ALSA devices by name. I will use as an example the soundcards on one of my Linux boxes, listed below:

charlie@CI327:~$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: Loopback [Loopback], device 0: Loopback PCM [Loopback PCM]
  Subdevices: 7/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7
card 0: Loopback [Loopback], device 1: Loopback PCM [Loopback PCM]
  Subdevices: 8/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7
card 1: PCH [HDA Intel PCH], device 0: ALC892 Analog [ALC892 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: PCH [HDA Intel PCH], device 1: ALC892 Digital [ALC892 Digital]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: PCH [HDA Intel PCH], device 3: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: PCH [HDA Intel PCH], device 7: HDMI 1 [HDMI 1]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: PCH [HDA Intel PCH], device 8: HDMI 2 [HDMI 2]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: PCH [HDA Intel PCH], device 9: HDMI 3 [HDMI 3]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: PCH [HDA Intel PCH], device 10: HDMI 4 [HDMI 4]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 2: USB [Scarlett 6i6 USB], device 0: USB Audio [USB Audio]
  Subdevices: 0/1
  Subdevice #0: subdevice #0
card 3: Device [USB Sound Device], device 0: USB Audio [USB Audio]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

You can see from the above output of the command "aplay -l" that there are four cards, numbered 0 through 3. Let's say I want to use card 2, the Scarlett 6i6. I need to know the name for the device and mode in which I Want to use it. So I issue the command "aplay -L" and search the output. I will just post the relevant part of that output:

front:CARD=USB,DEV=0
    Scarlett 6i6 USB, USB Audio
    Front speakers
surround21:CARD=USB,DEV=0
    Scarlett 6i6 USB, USB Audio
    2.1 Surround output to Front and Subwoofer speakers
surround40:CARD=USB,DEV=0
    Scarlett 6i6 USB, USB Audio
    4.0 Surround output to Front and Rear speakers
surround41:CARD=USB,DEV=0
    Scarlett 6i6 USB, USB Audio
    4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=USB,DEV=0
    Scarlett 6i6 USB, USB Audio
    5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=USB,DEV=0
    Scarlett 6i6 USB, USB Audio
    5.1 Surround output to Front, Center, Rear and Subwoofer speakers

If I want to use the Scarlett in 2 channel mode, where I would usually write:

hw:2,0

I write

front:CARD=USB,DEV=0

or

hw:CARD=USB,DEV=0

Under ALSA these names for the card never change, even if the card number does. Try it on your system.

 

[rpi]

Thank you CharlieLaub! It worked when I changed the lines in the .asoundrc from:

...
ctl.!default {
  type hw card 2
}
...
pcm.plugequal {
  type equal;
  slave.pcm "plughw:2,0";
}
...

to

...
ctl.!default {
  type hw CARD=PCM2702,DEV=0
}
...
pcm.plugequal {
  type equal;
  slave.pcm "plughw:CARD=PCM2702,DEV=0";
}
...

Best regards