Audio: Way to disable HDMI or set USB as default?

[Tim Curtis]

The alsactl save command is not used.

I'm not able to repro your issue by turning off my USB DAC then turning it back on a few minutes later.
moOde 930 | Pi-3B+ | Allo Revolution DAC

1. Pi and DAC powered on, DAC is assigned ALSA card 0
Startup log

Code:

20250412 105529 worker: --
20250412 105529 worker: -- ALSA debug
20250412 105529 worker: --
20250412 105529 worker: Cards:  0:Revolution      1:vc4hdmi         2:empty           3:empty           
20250412 105529 worker:         4:empty           5:empty           6:empty           7:empty           
20250412 105530 worker: Mixers: 0:(Revolution )   1:none            2:none            3:none            
20250412 105530 worker:         4:none            5:none            6:none            7:none            
20250412 105530 worker: --
20250412 105530 worker: -- Audio configuration
20250412 105530 worker: --
20250412 105530 worker: Audio device:  0:Allo Revolution DAC
20250412 105530 worker: ALSA card:     has not been reassigned
20250412 105530 worker: MPD config:    update not needed
20250412 105530 worker: ALSA output:   USB
20250412 105530 worker: ALSA mode:     Default (plughw)
20250412 105530 worker: ALSA mixer:    Revolution 
20250412 105531 worker: ALSA volume:   62% (-48.00dB)
20250412 105531 worker: ALSA maxvol:   100%
20250412 105531 worker: ALSA loopback: off
20250412 105531 worker: MPD mixer      Hardware
20250412 105531 worker: Integ audio:   vc4-kms-v3d
20250412 105531 worker: Audio formats: S16_LE, S32_LE, SPECIAL, DSD_U32_BE
20250412 105531 worker: CamillaDSP:    off
20250412 105531 worker: CDSP volume:   -51dB
20250412 105531 worker: CDSP volrange: 60dB

Audio Config
   
Debug showing the array thats used to populate the dropdown

Code:

20250412 105801 Array
(
    [0] => Allo Revolution DAC
    [1] => Pi HDMI 1
    [2] => empty
    [3] => empty
    [4] => empty
    [5] => empty
    [6] => empty
    [7] => empty
)

2. Power off the DAC
   

Code:

20250412 105834 Array
(
    [0] => empty
    [1] => Pi HDMI 1
    [2] => empty
    [3] => empty
    [4] => empty
    [5] => empty
    [6] => empty
    [7] => empty
)

3. Power on the DAC a few minutes later
   

Code:

20250412 110032 Array
(
    [0] => Allo Revolution DAC
    [1] => Pi HDMI 1
    [2] => empty
    [3] => empty
    [4] => empty
    [5] => empty
    [6] => empty
    [7] => empty
)