Hardware volume control & multiroom (SABAJ A30a)

[hiisukun]

Hey team. I have Moode set up in 3 rooms, and was attempting to make this a 'multi room' setup now. All three rooms are rasp pis, with combo dac+amps attached.

Unfortunately, the main room has a SABAJ A30a which does not seem to support 'hardware volume control'. I can include the full `lsusb` output if people need. Does anyone know of a way to test if this is a driver issue, vs just a limitation of the device? Can I load something at boot time of the pi, or make some software adjustment to enable this showing up?

Assuming I can't get the SABAJ to present that hardware volume: How strict is the requirement for hardware volume control when using multiroom? I would be happy to forego being able to adjust the volume on the app (and to use the knob on the amp instead), or to suffer any quality loss from 'software' volume control since it uses that at the moment and sounds fine. Perhaps there is a way to force enable multiroom receiver in the configuration, without using the gui, knowing that some parts will be broken.

Here's some `sudo alsacap` outputs:

Code:

# The SABAJ, no hardware volume control:
...
Card 2, ID `AUDIO', name `SABAJ USB AUDIO'
 Device 0, ID `USB Audio', name `USB Audio', 1 subdevices (1 available)
   2 channels, sampling rate 44100..768000 Hz
   Sample formats: S32_LE, SPECIAL, DSD_U32_BE
   Buffer size range from 16 to 1536000
   Period size range from 8 to 768000

     Subdevice 0, name `subdevice #0'

# An Aiyima T9, with hardware volume control:
...
Card 2, ID `Audio', name `USB HIFI Audio'
  Device 0, ID `USB Audio', name `USB Audio', 1 subdevices (1 available)
    2 channels, sampling rate 44100..192000 Hz
    Sample formats: S16_LE, S24_3LE
    Buffer size range from 22 to 384000
    Period size range from 11 to 192000

      Subdevice 0, name `subdevice #0'

And here is lsusb output showing hardware volume control entry on the Aiyima:

Code:

# Aiyima T9 Pro, partway through `lsusb -v -d 262a:9123`:
...
     AudioControl Interface Descriptor:
       bLength                18
       bDescriptorType        36
       bDescriptorSubtype      6 (FEATURE_UNIT)
       bUnitID                10
       bSourceID               3
       bmaControls(0)     0x00000003
         Mute Control (read/write)
       bmaControls(1)     0x0000000c
         Volume Control (read/write)
       bmaControls(2)     0x0000000c
         Volume Control (read/write)
       iFeature                0

The output of lsusb for the SABAJ sadly has no similar entry (nothing "FEATURE_UNIT" or with 'Volume' in it). Though it does have a lot of stuff.

Moode version is 8.3.0 on all the units, and the firmware on the SABAJ is MCU_FW_220928, for what it's worth. It's specs say it uses an "XMOS XU208 USB Interface".

Happy to post any other logs if people are interested and can offer advice.