Mixxx taking just one soundcard

Debug [Main]: Mixxx 1.11.0 "(bzr 1.11 r3885+; built on: Apr 25 2014 @ 04:15:09; flags: bulk hid hifieq mad optimize=9 qdebug shoutcast vamp verbose vinylcontrol)" is starting...
Debug [Main]: Qt version is: 4.8.6
Debug [Main]: Configuration file is at the current version 1.11.0
Debug [Main]: Loading translations for locale "de_DE" from translations folder "/usr/share/mixxx/translations/" : success
Debug [Main]: ConfigObject: Could not read ""
Warning [Main]: ControlObject::getControl returning NULL for ( "[Channel1]" , "vinylcontrol_mode" )
Warning [Main]: ControlObject::getControl returning NULL for ( "[Channel2]" , "vinylcontrol_mode" )
Debug [Main]: JACK client name set
ALSA lib pcm_dsnoop.c:618:(snd_pcm_dsnoop_open) unable to open slave
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe
ALSA lib pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side
bt_audio_service_open: connect() failed: Connection refused (111)
bt_audio_service_open: connect() failed: Connection refused (111)
bt_audio_service_open: connect() failed: Connection refused (111)
bt_audio_service_open: connect() failed: Connection refused (111)
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
jack server is not running or cannot be started
Warning [Main]: ControlObject::getControl returning NULL for ( "[Flanger]" , "lfoDepth" )
Warning [Main]: ControlObject::getControl returning NULL for ( "[Flanger]" , "lfoDelay" )
Warning [Main]: ControlObject::getControl returning NULL for ( "[Flanger]" , "lfoPeriod" )
Debug [Main]: Available QtSQL drivers: ("QSQLITE")
Debug [Main]: DB status: "/home/rene/.mixxx/mixxxdb.sqlite" = true
Debug [Main]: SchemaManager::upgradeToSchemaVersion already at version 17
Debug [Main]: TrackDAO::initialize QThread(0xe6ca50, name = "Main") "qt_sql_default_connection"
Debug [Main]: CrateDAO::initialize()
Debug [Main]: CueDAO::initialize QThread(0xe6ca50, name = "Main") "qt_sql_default_connection"
Debug [Main]: Default quick links: ("/home/rene/Musik/Hai-Life/DJ-Set/", "/home/rene/Musik/", "/home/rene/Downloads/", "/home/rene/Schreibtisch/", "/home/rene/Dokumente/")
Debug [Main]: Appending Quick Link: "DJ-Set" --- "/home/rene/Musik/Hai-Life/DJ-Set/"
Debug [Main]: Appending Quick Link: "Musik" --- "/home/rene/Musik/"
Debug [Main]: Appending Quick Link: "Downloads" --- "/home/rene/Downloads/"
Debug [Main]: Appending Quick Link: "Schreibtisch" --- "/home/rene/Schreibtisch/"
Debug [Main]: Appending Quick Link: "Dokumente" --- "/home/rene/Dokumente/"
Debug [Main]: Creating session history playlist name: "2015-04-16 (10)"
Debug [Main]: Committing transaction on "qt_sql_default_connection" result: true
Debug [Main]: Traktor Library Location=[ "/home/rene/collection.nml" ]
Debug [Main]: AnalyserWaveform::AnalyserWaveform()
Debug [Main]: Setting VAMP_PATH to: "/usr/lib/mixxx/plugins/vamp:/home/rene/.mixxx/plugins/vamp/:/usr/bin/lin32_build/vamp-plugins:/usr/bin/lin64_build/vamp-plugins"
Debug [Main]: Creating ControllerManager
Debug [Main]: Extension ".bulk.xml" total 1 presets
Debug [Main]: Extension ".hid.xml" total 7 presets
Debug [Main]: Extension ".midi.xml" total 79 presets
Debug [Main]: Setting VAMP_PATH to: "/usr/lib/mixxx/plugins/vamp:/home/rene/.mixxx/plugins/vamp/:/usr/bin/lin32_build/vamp-plugins:/usr/bin/lin64_build/vamp-plugins:/usr/lib/mixxx/plugins/vamp:/home/rene/.mixxx/plugins/vamp/:/usr/bin/lin32_build/vamp-plugins:/usr/bin/lin64_build/vamp-plugins"
Debug [Main]: VampPluginLoader::listPlugins() returned 3 plugins
Debug [Main]: Plugin output displayname: "mixxxbpmdetection:0" "SoundTouch BPM Detector (Legacy)"
Debug [Main]: Plugin output displayname: "qm-barbeattracker:0" "Bar and Beat Tracker"
Debug [Main]: Plugin output displayname: "qm-barbeattracker:1" "Bar and Beat Tracker"
Debug [Main]: Plugin output displayname: "qm-barbeattracker:2" "Bar and Beat Tracker"
Debug [Main]: Plugin output displayname: "qm-barbeattracker:3" "Bar and Beat Tracker"
Debug [Main]: Plugin output displayname: "qm-tempotracker:0" "Queen Mary Tempo and Beat Tracker"
Debug [Main]: Plugin output displayname: "qm-tempotracker:1" "Queen Mary Tempo and Beat Tracker"
Debug [Main]: Plugin output displayname: "qm-tempotracker:2" "Queen Mary Tempo and Beat Tracker"
Debug [Main]: ControllerManager::getControllerList
Debug [Main]: SoundManager::setupDevices()
Debug [Main]: SoundDevicePortAudio::open() "3, SB X-Fi Surround 5.1 Pro: USB Audio (hw:1,0)"
Debug [Main]: framesPerBuffer: 4096
Debug [Main]: Requested sample rate: 48000 Hz, latency: 85.3333 ms
Debug [Main]: Output channels: 2 | Input channels: 0
Debug [Main]: Opening stream with id 3
Debug [Main]: Opened PortAudio stream successfully... starting
Debug [Main]: Dynamically loaded PortAudio library
Debug [Main]: PortAudio: Started stream successfully
Debug [Main]: Actual sample rate: 48000 Hz, latency: 85.3333 ms
Debug [Main]: SoundDevicePortAudio::open() "1, HDA Intel: 92HD71B7X Digital (hw:0,1)"
Debug [Main]: framesPerBuffer: 4096
Debug [Main]: Requested sample rate: 48000 Hz, latency: 85.3333 ms
Debug [Main]: Output channels: 2 | Input channels: 0
Debug [Main]: Opening stream with id 1
Debug [Main]: Opened PortAudio stream successfully... starting
Debug [Main]: Dynamically loaded PortAudio library
Debug [Main]: PortAudio: Started stream successfully
Debug [Main]: Actual sample rate: 48000 Hz, latency: 85.3333 ms
Debug [Main]: Using "HDA Intel: 92HD71B7X Digital (hw:0,1)" as output sound device clock reference
Debug [Main]: 2 output sound devices opened
Debug [Main]: 0 input sound devices opened
Debug [Main]: Set root GL Context widget valid: QGLWidget(0x1968100) true
Debug [Main]: Created root GL Context valid: 0x19684f0 true
Debug [Main]: Root GL Context format:
Debug [Main]: Double Buffering: true
Debug [Main]: Swap interval: 0
Debug [Main]: Depth buffer: true
Debug [Main]: Direct rendering: true
Debug [Main]: Has overlay: false
Debug [Main]: RGBA: true
Debug [Main]: Sample buffers: false
Debug [Main]: Stencil buffers: true
Debug [Main]: Stereo: false
Warning [Main]: ControlObject::getControl returning NULL for ( "[Spinny1]" , "show_spinny" )
Warning [Main]: Requested control does not exist: "[Spinny1],show_spinny" Creating it.
Warning [Main]: ControlObject::getControl returning NULL for ( "[Spinny2]" , "show_spinny" )
Warning [Main]: Requested control does not exist: "[Spinny2],show_spinny" Creating it.
Warning [Main]: ControlObject::getControl returning NULL for ( "[Samplers]" , "show_samplers" )
Warning [Main]: Requested control does not exist: "[Samplers],show_samplers" Creating it.
Warning [Main]: ControlObject::getControl returning NULL for ( "[Microphone]" , "show_microphone" )
Warning [Main]: Requested control does not exist: "[Microphone],show_microphone" Creating it.
Warning [Main]: ControlObject::getControl returning NULL for ( "[Vinylcontrol]" , "show_vinylcontrol" )
Warning [Main]: Requested control does not exist: "[Vinylcontrol],show_vinylcontrol" Creating it.
Warning [Main]: ControlObject::getControl returning NULL for ( "[PreviewDeck]" , "show_previewdeck" )
Warning [Main]: Requested control does not exist: "[PreviewDeck],show_previewdeck" Creating it.
Debug [Main]: Invalid node name in skin: "manifest"
Debug [Main]: Making property binder for "visible"
Warning [Main]: WaveformSignalColors::fallBackFromSignalColor - skin do not provide low/mid/high signal colors
Warning [Main]: ControlObject::getControl returning NULL for ( "[Sampler1]" , "" )
Warning [Main]: WaveformSignalColors::fallBackFromSignalColor - skin do not provide low/mid/high signal colors
Warning [Main]: ControlObject::getControl returning NULL for ( "[Sampler2]" , "" )
Warning [Main]: WaveformSignalColors::fallBackFromSignalColor - skin do not provide low/mid/high signal colors
Warning [Main]: ControlObject::getControl returning NULL for ( "[Sampler3]" , "" )
Warning [Main]: WaveformSignalColors::fallBackFromSignalColor - skin do not provide low/mid/high signal colors
Warning [Main]: ControlObject::getControl returning NULL for ( "[Sampler4]" , "" )
Debug [Main]: Making property binder for "visible"
Warning [Main]: ControlObject::getControl returning NULL for ( "[PreviewDeck1]" , "" )
Debug [Main]: Recordings folder set to "/media/rene/Elements/Hai-Life/Mixxx/Recordings"
Debug [Main]: BaseTrackCache(0x1790ad0) updateIndexWithQuery took 105 ms
Debug [Main]: PrepareLibraryTableModel(0x235a520) select() took 151 ms
Debug [Main]: PrepareLibraryTableModel(0x235a520) select() took 39 ms
Debug [Main]: DlgPrepare(0x230fa50, name = "DlgPrepare") analysisActive false
Debug [Main]: Making property binder for "visible"
Debug [Main]: Making property binder for "visible"
Debug [Main]: Created QGLWidget. Context Valid: true Sharing: true
Warning [Main]: WaveformSignalColors::fallBackFromSignalColor - skin do not provide low/mid/high signal colors
Warning [Main]: ControlObject::getControl returning NULL for ( "[Channel1]" , "" )
Debug [Main]: WaveformWidgetFactory::setWaveformWidget - waveform widget added in factory, index 0
Debug [Main]: Making property binder for "visible"
Debug [Main]: WSpinny(): Created QGLWidget, Context Valid: true Sharing: true
Warning [Main]: WaveformSignalColors::fallBackFromSignalColor - skin do not provide low/mid/high signal colors
Warning [Main]: ControlObject::getControl returning NULL for ( "[Channel1]" , "" )
Debug [Main]: Created QGLWidget. Context Valid: true Sharing: true
Warning [Main]: WaveformSignalColors::fallBackFromSignalColor - skin do not provide low/mid/high signal colors
Warning [Main]: ControlObject::getControl returning NULL for ( "[Channel2]" , "" )
Debug [Main]: WaveformWidgetFactory::setWaveformWidget - waveform widget added in factory, index 1
Debug [Main]: Making property binder for "visible"
Debug [Main]: WSpinny(): Created QGLWidget, Context Valid: true Sharing: true
Warning [Main]: WaveformSignalColors::fallBackFromSignalColor - skin do not provide low/mid/high signal colors
Warning [Main]: ControlObject::getControl returning NULL for ( "[Channel2]" , "" )
Debug [Main]: MixxxLibraryFeature::activate()
Debug [Main]: LibraryTableModel(0x17a9170) select() took 36 ms
Debug [Main]: WSearchLineEdit::restoreSearch( "" )
Debug [Controller]: ControllerManager: Setting up devices
Debug [Controller]: Scanning PortMIDI devices:
Debug [Main]: Constructed LibraryScanner
Debug [Main]: iTunes Album Art path is: ""
Debug [Main]: Displaying mixxx
Debug [Controller]: Scanning USB Bulk devices:
Debug [Controller]: Scanning HID devices:
Debug [Controller]: Found 0x0 0x0 "r4609" S/N 0x0 "Interface 0"
Warning [Controller]: USB permissions problem (or device error.) Your account needs write access to USB HID controllers.
Debug [Controller]: Found 0x0 0x0 "r4609" S/N 0x0 "Interface 1"
Warning [Controller]: USB permissions problem (or device error.) Your account needs write access to USB HID controllers.
Debug [Controller]: Found 0x0 0x0 "r4609" S/N 0x0 "Interface 2"
Warning [Controller]: USB permissions problem (or device error.) Your account needs write access to USB HID controllers.
Debug [Controller]: Found 0x0 0x0 "r256" S/N 0x0 "Interface 0"
Warning [Controller]: USB permissions problem (or device error.) Your account needs write access to USB HID controllers.
Debug [Controller]: Found 0x0 0x0 "r256" S/N 0x0 "Interface 0"
Warning [Controller]: USB permissions problem (or device error.) Your account needs write access to USB HID controllers.
Debug [Controller]: ControllerManager::getControllerList
Debug [Controller]: Controller polling stopped.
Debug [Main]: resize QSize(1366, 725)
Debug [Main]: Running Mixxx
Warning [Main]: WaveformRenderBackground::generateImage() - file( "/usr/share/mixxx/skins/Deere1366x768-WXGA/style/style_bg_waveform.png" ) 415 x 119 do not fit the waveform widget size 339 x 119
Warning [Main]: WaveformRenderBackground::generateImage() - file( "/usr/share/mixxx/skins/Deere1366x768-WXGA/style/style_bg_waveform.png" ) 415 x 119 do not fit the waveform widget size 337 x 119

According to the log it looks like both soundcards configured correct:

3, SB X-Fi Surround 5.1 Pro: USB Audio (hw:1,0)
HDA Intel: 92HD71B7X Digital (hw:0,1)

Please note that the cinnamon sound preferences interfere with the settings in MIxxx, do not touch them.
Be sure all sound card mixer controls are setup correct by starting "alsamixer" from the terminal.

By the way, it is not recommended to use two soundcards in Mixxx 1.11. It will likely produce clicks in the headphone because of the differences of the two clock sources.
From 1.12 alpha Mixxx is able to sync the soundcards correctly.

You will find optimized build in Nicos repro https://launchpad.net/~nschloe/+archive/ubuntu/mixxx-nightly

If it does not work you may attach a screenshot of your hardware preferences in Mixxx.

Please keep us updated in any case.