Troubleshooting new USB audio device

[Caelia Chapin <crc@xxxxxxxxxx>]

Hello, all--

I have a brand new Denon MCX8000 DJ controller which I would like to use with Mixxx (open source DJ software) on my Linux laptop. If you're not familiar with DJ controllers, it's basically a MIDI controller that includes its own sound card. Denon does not publish detailed specs for the sound card, but it is a 24-bit, 44100k, USB 2.0 audio device. And since this particular controller can run standalone (i.e. unconnected to any computer), I have determined that the sound card works - that is, it plays music and sounds fine.

However, I am having trouble getting the sound working with Linux. My system is a Lenovo Thinkpad T410 running 64-bit Manjaro Linux, with all packages updated last night - so I have version 1.1.3 of alsa-lib and alsa-utils.

Here's what I'm finding:

   aplay -l
   ....
   card 1: MCX8000 [DENON DJ MCX8000], device 0: USB Audio [USB Audio]
     Subdevices: 1/1
     Subdevice #0: subdevice #0

   aplay -L
   ....
   default:CARD=MCX8000
      DENON DJ MCX8000, USB Audio
      Default Audio Device
   sysdefault:CARD=MCX8000
      DENON DJ MCX8000, USB Audio
      Default Audio Device
   ....

   [additional entries for various values of surroundNN]

When I run alsamixer, DENON DJ MCX8000 is one of the sound cards I can select; when I do select it, the results depend on the kernel version. With older kernels, no playback or capture devices are shown for this card; with a 4.9 or 4.10 kernel, a single playback device is shown:

   MULTI Validity

However, the info at the top of the screen says it is [Off], and in the center of screen where a volume slider might be, MM is displayed - meaning "muted," I suppose. And there does not seem to be any way to change the state of that control.

Finally, the crux of the matter. When I run Mixxx and attempt to select the MCX8000 as the output device, the GUI pops up an "unknown error" message. But when I run Mixxx in debug mode, I am able to capture following more detailed error:

   Debug [Main]: Opening stream with id 4
   _expression_ 'r' failed in 'src/hostapi/alsa/pa_linux_alsa.c', line: 2092
   _expression_ 'PaAlsaStreamComponent_FinishConfigure( &self->playback, hwParamsPlayback, outParams, self->primeBuffers, realSr, outputLatency )' failed in 'src/hostapi/alsa/pa_linux_alsa.c', line: 2733
   _expression_ 'PaAlsaStream_Configure( stream, inputParameters, outputParameters, sampleRate, framesPerBuffer, &inputLatency, &outputLatency, &hostBufferSizeMode )' failed in 'src/hostapi/alsa/pa_linux_alsa.c', line: 2838
   Warning [Main]: Error opening stream: Unanticipated host error

So, is anyone able to understand what the issue is here? Is there any hope of getting this soundcard working? Any suggestions for additional troubleshooting?

Thanks in advance for any insights.

--

Caelia Chapin

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