Problem with pulseaudio showing only 2 input channels

Problem with pulseaudio showing only 2 input channels

Hello everybody,

i want to use a MixPre-10 II (from Sound Device) to capture multiple microphones (up to 5 or 6) at the same time and analyze the signals on a computer.
The MixPre-10 II is connected via USB-C to a pc running Ubuntu OS and a python script including pyaudio to capture the multiple channels.

The problem is that pavucontrol (and Audacity e.g.) only shows 2 input channels.

The MixPre-10 II is configured correctly, because on a Mac OS every 12 input channels are shown.

‘pacmd list-sources’ produces the following output:


* index: 11
    state: SUSPENDED
    suspend cause: IDLE
    priority: 9048
    volume: front-left: 65536 / 100% / 0,00 dB,  front-right: 65536 / 100% / 0,00 dB
            balance 0,00
    base volume: 65536 / 100% / 0,00 dB
    volume steps: 65537
    muted: no
    current latency: 0,00 ms
    max rewind: 0 KiB
    sample spec: s16le 2ch 44100Hz
    channel map: front-left,front-right
    used by: 0
    linked by: 0
    configured latency: 0,00 ms; range is 0,50 .. 2000,00 ms
    card: 6
    module: 33
        alsa.resolution_bits = "16"
        device.api = "alsa"
        device.class = "sound"
        alsa.class = "generic"
        alsa.subclass = "generic-mix" = "USB Audio" = "USB Audio"
        alsa.subdevice = "0"
        alsa.subdevice_name = "subdevice #0"
        alsa.device = "0"
        alsa.card = "1"
        alsa.card_name = "MixPre-10 II"
        alsa.long_card_name = "Sound Devices, LLC MixPre-10 II at usb-0000:00:14.0-3, high speed"
        alsa.driver_name = "snd_usb_audio"
        device.bus_path = "pci-0000:00:14.0-usb-0:3:1.0"
        sysfs.path = "/devices/pci0000:00/0000:00:14.0/usb1/1-3/1-3:1.0/sound/card1" = "usb-Sound_Devices__LLC_MixPre-10_II_TJ0120085001-00"
        device.bus = "usb" = "0926" = "Sound Devices, LLC" = "0210" = "MixPre-10 II"
        device.serial = "Sound_Devices__LLC_MixPre-10_II_TJ0120085001"
        device.string = "iec958:1"
        device.buffering.buffer_size = "352800"
        device.buffering.fragment_size = "176400"
        device.access_mode = "mmap+timer" = "iec958-stereo"
        device.profile.description = "Digital Stereo (IEC958)"
        device.description = "MixPre-10 II Digital Stereo (IEC958)"
        alsa.mixer_name = "USB Mixer"
        alsa.components = "USB0926:0210"
        module-udev-detect.discovered = "1"
        device.icon_name = "audio-card-usb"
        iec958-stereo-input: Digital Input (S/PDIF) (priority 0, latency offset 30000 usec, available: unknown)
    active port:

If i change the soundcard to MixPre-10 II in alsamixer, the message “This sound device does not have any controls” appears.

I suspect it has something to do with PulseAudio, but as I have very little experience in this field, I wanted to ask if anyone had a similar problem or has any idea how to face the problem.

Many thanks in advance!


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