Raspberry - Two USB DAC

[Fabio]

Hi everybody,

I am quite new with Moode and my experience till now is very very positive.
At the moment I only have a (minor) issue ... and I would like to solve if possible.

I use 6.4.2 on Pi3B+ (Connected to the network by Ethernet cable) to drive an USB external DAC.

In deed I have two USB DACs and I tried to connect both of them to Raspberry but they are both already on when the system goes up and this seems to create random problems in their recognition.
Some time the system is able to work with one of them, some time it does not work at all. In any case it seems there is no a smooth way to switch from one to the other.

I tried also to keep the DACs in stand-by while moode starts up, but it does not work well anyway
and the random behave is still there.
The only way I found choose a specific DAC and get it working, is to phisically connect only one DAC to Pi - that is not the most elegant solution.

Is this limitation expected or it is only my poor knowledge of the system?

Thank you for suggestions.
  Fabio

[Tim Curtis]

What make and model are the DAC's?

[Fabio]

Thank you for your answer Tim,

They are:
Marantz Hd-DaC1 - Headphone amp + DAC
North Star Blue Diamond - Inegrated amp + DAC

But I think that Mood behave could be the same whaterver couple of DAC is connected to Pi because both my DACs work perfectly when connected standalone.

Fabio

[Tim Curtis]

ALSA USB audio hot plugging and swapping are not what I'd call reliable. Standby mode and wakeup also IME have not been reliably detected by ALSA.

Heres some information about ALSA hot plugging. Note that none of the scripts or procedures mentioned in the HowTo have ever been implemented in moOde. The only thing moOde does explicitly for USB audio is to regularly save the ALSA state when a USB audio device is configured. The "save" occurs during worker.php 3 second event loop, so every 3 secs.
https://alsa.opensrc.org/Hotplugging_USB...es_(Howto)

[Fabio]

uhm ... it is more complex than I initally thought.

I’ll move to an HW solution adding a passive USB switch just to avoid playing with cables every time.
It is a cheap solution that I am quite sure will not impact the ‘sound quality’ (we are on the digital path).
The drawback is that l’ll have to chose my DAC before turning on the Pi but it is a minor issue.

Thank you Tim,
Fabio

[mtnbrit]

Or maybe add a second $35 rPi, one for each DAC?

[gwurb]

ALSA USB audio hot plugging and swapping are not what I'd call reliable. Standby mode and wakeup also IME have not been reliably detected by ALSA.

Heres some information about ALSA hot plugging. Note that none of the scripts or procedures mentioned in the HowTo have ever been implemented in moOde. The only thing moOde does explicitly for USB audio is to regularly save the ALSA state when a USB audio device is configured. The "save" occurs during worker.php 3 second event loop, so every 3 secs.
https://alsa.opensrc.org/Hotplugging_USB...es_(Howto)

Does Moode have any ability to power down USB ports after a period of inactivity, allowing the USB DACs to go into standby? Of course it would need to power the port back up prior to commencing playback...

[CallMeMike]

ALSA USB audio hot plugging and swapping are not what I'd call reliable. Standby mode and wakeup also IME have not been reliably detected by ALSA.

Heres some information about ALSA hot plugging. Note that none of the scripts or procedures mentioned in the HowTo have ever been implemented in moOde. The only thing moOde does explicitly for USB audio is to regularly save the ALSA state when a USB audio device is configured. The "save" occurs during worker.php 3 second event loop, so every 3 secs.
https://alsa.opensrc.org/Hotplugging_USB...es_(Howto)

Does Moode have any ability to power down USB ports after a period of inactivity, allowing the USB DACs to go into standby? Of course it would need to power the port back up prior to commencing playback...

You may get a better 'audience' and possibly help/clues if you start a new thread...