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Denon Prime hardware does not use the RK3288’s built-in audio interfaces for DJ output. Instead, the SoC hands off digital audio over an internal USB 2.0 bus to a dedicated XMOS USB audio controller, which feeds professional-grade AKM converters. MIXXX targets these converters directly through ALSA, with no intermediate audio server in the path.

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Hardware Signal Chain

Rockchip RK3288 (CPU/mixer)
  → ALSA (kernel audio subsystem)
    → USB 2.0 (internal bus)
      → XMOS XS1-U6A-64-FB96 (USB audio controller)
        → AKM AK4621 CODEC (main I/O: master out, booth, headphone)
        → AKM AK4413 DAC (secondary channels)
The RK3288 does not perform any analog conversion. All DAC operations happen inside the AKM chips downstream of the XMOS controller. This means CPU load from MIXXX’s audio engine has no direct impact on analog output quality — the XMOS controller handles USB isochronous transfers independently.

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Why Direct ALSA

Engine OS is a stripped-down Buildroot Linux environment with no PulseAudio, JACK, or PipeWire installed. The only audio infrastructure present is alsa-utils version 1.2.4. MIXXX’s ALSA backend communicates directly with the kernel’s ALSA layer, which maps to the XMOS USB audio device via the snd-usb-audio kernel module. There is no intermediate daemon to configure, no session management, and no permission model beyond the running user’s access to /dev/snd/*.

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Sound Cards on Prime Go

card 0 [Surface] : USB-Audio - PRIME GO Control Surface
                   Denon DJ PRIME GO Control Surface at usb-ff540000.usb-1, full speed
card 1 [JP11]    : JP11 - JP11
                   JP11
There are two ALSA cards exposed by the hardware:

Card 0: Surface (USB Control Surface)

Handles MIDI/HID communication with the hardware controls: jog wheels, faders, buttons, pads, and encoders. Not for audio output. Configuring MIXXX to output to card 0 will produce silence.

Card 1: JP11 (XMOS Audio Interface)

The main XMOS audio interface connected to the AK4621 CODEC and AK4413 DAC. This is the correct target for all MIXXX audio output. Use hw:1,0 or the named form hw:JP11,0.

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ALSA Diagnostic Commands

# List all sound cards
cat /proc/asound/cards
aplay -l
aplay -L

# List PCM devices for the JP11 audio interface
aplay -D hw:JP11 --list-pcms

# Test audio output (verify connections before a gig — watch your volume)
speaker-test -D hw:JP11 -c 2 -t sine -f 440

# Inspect ALSA mixer controls for the JP11 card
amixer -c JP11 contents
amixer -c JP11 controls

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Releasing ALSA Hardware Locks

Engine OS’s DJ application (“Planck”) takes exclusive control of the ALSA interfaces at boot. MIXXX cannot open the JP11 ALSA device while Engine OS holds the lock. The TKGL bootstrap module handles this automatically by calling systemctl stop engine before launching MIXXX. If you are launching MIXXX manually (for debugging or from a switcher script), you must release the lock first: 
systemctl stop engine
Attempting to open hw:JP11,0 while Engine OS is running will result in a Device or resource busy error from ALSA.

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Pre-Configured soundconfig.xml

MIXXX normally enumerates all available ALSA PCM devices via PortAudio before presenting the audio preferences dialog. On Prime hardware, this enumeration can be slow or problematic (see the PortAudio NDEBUG section below). Providing a soundconfig.xml file causes MIXXX to skip enumeration and open the specified device directly: 
<?xml version="1.0" encoding="utf-8"?>
<SoundManagerConfig>
  <SoundDevice name="JP11: PCM inmusic,jp11-audio-codec-0 (hw:1,0)" api="ALSA">
    <output_channels>4</output_channels>
    <sample_rate>44100</sample_rate>
  </SoundDevice>
</SoundManagerConfig>
Place this file at /media/az01-internal/mixxx/settings/soundconfig.xml. The --settingsPath argument in the launcher points MIXXX to this directory, so no additional configuration is needed.

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ALSA Buffer Tuning

Buffer size is the primary lever for latency. Smaller buffers reduce latency but increase the risk of xruns (buffer underruns) when the CPU is briefly unavailable to the audio callback.
ParameterValueDerived latency
Devicehw:JP11,0Direct hardware, no software conversion
FormatS32_LE32-bit signed little-endian
Channels4Main L/R + booth/headphone
Sample rate44100 Hz—
latency setting5—
period_size1024 frames23.2 ms per callback
buffer_size2048 frames46.4 ms total ring buffer
Setting latency=4 (period_size=512, 11.6 ms per period) causes regular xruns when the Mali GPU is active. GPU DMA bursts create brief memory bus stalls that the 11.6 ms period cannot absorb. Use latency=5 (period_size=1024) as the minimum safe value on this hardware.If soundconfig.xml contains latency="4", MIXXX will report period_size=512 — double the buffer to 1024 to resolve xruns.

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PortAudio NDEBUG Fix

The Buildroot PortAudio package (V19.7.0-devel) is compiled without the NDEBUG preprocessor define, leaving all C assert() calls active in the release binary. During ALSA device enumeration, PortAudio’s GropeDevice() function probes plugin PCMs on the JP11 hardware. Some of these PCMs report 0 channels, triggering: 
assert(maxChans > 0) → SIGABRT → crash
This crash happens inside pa_linux_alsa.c before MIXXX has finished initialising.
Fix: Add -DNDEBUG to PortAudio’s CFLAGS in package/portaudio/portaudio.mk via a post-configure hook. This disables all assertions at compile time.The complete modified file is available at patches/portaudio-ndebug.mk in the repository. Apply it during the Buildroot compile step, not on the device.Verification: A standalone test binary (minipa_arm, built from test/minipa.c) calls Pa_Initialize() + Pa_GetDeviceCount() and confirms:
  • 4 ALSA devices found (no crash)
  • JP11 device: PCM inmusic,jp11-audio-codec-0 (hw:1,0) — 2 inputs, 4 outputs
If the NDEBUG patch is not applied, Pa_Initialize() crashes before returning and MIXXX never reaches its main window.

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Verification Checklist

Run these checks after any audio configuration change to confirm the full chain is working:
1

Confirm cards are present

cat /proc/asound/cards
Expect to see card 0 (Surface) and card 1 (JP11).
2

Confirm Engine OS is stopped

systemctl is-active engine
Should return inactive. If active, run systemctl stop engine.
3

Test ALSA output directly

speaker-test -D hw:JP11 -c 2 -t sine -f 440
You should hear a 440 Hz sine wave on the main outputs.
4

Verify soundconfig.xml path

cat /media/az01-internal/mixxx/settings/soundconfig.xml
Confirm the device name matches JP11: PCM inmusic,jp11-audio-codec-0 (hw:1,0).
5

Check MIXXX settings path in launcher

grep settingsPath /media/az01-internal/mixxx/mixxx_launcher.sh
Confirm --settingsPath points to the same directory as soundconfig.xml.

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