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

[sultanoswing]

I've got my Pi4 moode plugged in to an SMSL C200 via USB. The set up works and sounds great.

I then power down the C200 DAC at the end of a listening session, but leave the Pi 4 powered on.

However, when I power on the C200 for the next session, the Pi / moode has defaulted to "0 : Pi HDMI 1", and needs a manual switch (Configure -> Audio -> Output device) back to "3: SMSL USB" every time. I don't recall this occurring under moode v8.x for what that's worth.

Is there a way to automate this e.g. by disabling the Pi HDMI outputs, or other workaround?

[Tim Curtis]

I ran a quick test and am not able to repro your issue.

1. Power off Allo Revolution DAC (USB)
2. Leave Pi running
3. Wait a bit
4. Power on DAC

Audio Config still shows Output device set to "0:Allo Revolution DAC"

Couple things I did noticed after powering on the DAC.
- Its hardware volume level reset to -127dB
- Moode volume knob was not responsive for about half a minute although that DAC hardware volume was being changed.

In moode 8 series (Bullseye), ALSA device/card assignments were fixed but in moode 9 series (Bookworm) ALSA uses dynamic device/card assignments i.e. during startup ALSA may assign a given audio device a card number different from what was assigned previously.

Why not just leave your DAC on?

[sultanoswing]

Audio Config still shows Output device set to "0:Allo Revolution DAC"

In moode 8 series (Bullseye), ALSA device/card assignments were fixed but in moode 9 series (Bookworm) ALSA uses dynamic device/card assignments i.e. during startup ALSA may assign a given audio device a card number different from what was assigned previously.

Why not just leave your DAC on?

You probably can't repro the issue since moode defaults to the first device ('0'), and in your case, it looks like the DAC is assigned to '0'. Question - do you have HDMI devices listed?

In a shell, alsamixer lists the sound cards as "default : 0 vc4-hdmi-0" and "default : 1 vc4-hdmi-1".

The fixed vs dynamic assignments almost certainly explains the new behaviour. I think if there's a way to stop the HDMI port being detected as an audio device, then that should work.

Do you how much power costs these days?

Yeah - no biggie as a workaround, but equally, not clean or efficient !

[Tim Curtis]

Couple things.

1. The HDMI ports can't be disabled or turned off in Bookworm.
2. I was testing on a Pi 3B+ which has 1 HDMI port. ALSA card 0 is Rev DAC and card 1 is Pi HDMI 1.
3. Re cost of power. The US where I live has a high cost of living relative to other countries and for sure things get turned off when not being used.

I'm not sure your issue is because of ALSA card reassignment. I'll run some tests later today on a Pi 4 and see what happens.

[Tim Curtis]

I'm not seeing any issues on my end with USB DAC power off/on with Pi4 running.

[Nutul]

Just saying... are you sure that a reboot didn't take place while your DAC was turned off?
I do as you, at the end of the session I switch my (USB) DAC off, but when I turn it back on, my moOde is happy.
If a reboot happens, by night, say for a quick power glitch, in the morning I see no DAC and have to reboot the Pi withe the DAC turned on.

[sultanoswing]

Just saying... are you sure that a reboot didn't take place while your DAC was turned off?
I do as you, at the end of the session I switch my (USB) DAC off, but when I turn it back on, my moOde is happy.

Hmmm. That might have been the case. Had the DAC off, Pi 4 on all day, then when I turned on the DAC this evening it has connected as the default output.

Can park this one for now, thanks all.

[TamedShrew]

I also have a SMSL DAC with a RPi4 and get this problem once in a while. I keep the RPi on, but turn off the DAC when I'm not listening to music. Unfortunately I cannot see any pattern to why it happens.

I never get the problem with my other 2 Moode setups using DACs from other manufacturers.

[nikolas]

Sorry to get back to an old thread, but I'm trying to see whether there is a good solution to the issue that remained unsolved here: If moode restarts while the USB output device is off, it resets the output to HDMI. This neither changes when the USB device is started and once output is set to HDMI, it also doesn't seem to revert to USB when restarting moode while the USB output is on. So the only way to fix this seems to be to reset output to USB manually. That works until the next reboot (or longer if the USB device is on during boot). I am just wondering whether there is a smarter way to fix this. Maybe moode could remember the device or one could set output to USB by default and moode could keep looking for it. Or if there is a way to change output from the command line, I could just run that every once in a while.

Just wondering whether there is a simple solution. Its simple enough to fix manually and doesn't happen too often. But when it happens, I always spend a few hours without music before I realize that I just need to set output back to USB. Thank you for your thoughts and all the work you put into this project - I've been enjoying it for a long time already!

[Nutul]

But when it happens, I always spend a few hours without music before I realize that I just need to set output back to USB.

A few hours??? How can you possibly not realize IMMEDIATELY that there is no music, go into the configuration and (re)set the output to USB?
Or... have a procedure to follow: turn USB device ON, then turn moOde ON?
(I do not have this kind of headache, as my moOde box is on 24/7, but I would do exactly that, was I switching everything off, say, at night)

I understand that this could be annoying, but it literally takes less than 10 seconds... I mean, this would at least keep you from spending "a few hours" without music.