Configuração de som atual (integrado Realtek ALC662) no Ubuntu 12.04 reproduz tudo como mono. Como corrigi-lo?

Question

Todos os ficheiros de música são reproduzidos como mono na minha instalação do Ubuntu 12.04.

Placa de som do sistema (integrada): Áudio de alta definição nVidia MCP61 (Realtek ALC662).
Alguém teve o mesmo problema? Qual é a solução?

Eu não sei muito sobre drivers Linux / kernels / modules etc.

Alguns comandos e seus resultados abaixo, talvez eles possam dizer algo

sudo lspci -v

00:05.0 Audio device: NVIDIA Corporation MCP61 High Definition Audio (rev a2)
    Subsystem: Micro-Star International Co., Ltd. Device 7309
    Flags: bus master, 66MHz, fast devsel, latency 0, IRQ 22
    Memory at febf4000 (32-bit, non-prefetchable) [size=16K]
    Capabilities: [44] Power Management version 2
    Capabilities: [50] MSI: Enable- Count=1/1 Maskable+ 64bit+
    Capabilities: [6c] HyperTransport: MSI Mapping Enable- Fixed+
    Kernel driver in use: snd_hda_intel
    Kernel modules: snd-hda-intel

lsmod | grep snd

snd_hda_codec_realtek   174313  1 
snd_hda_intel          32765  6 
snd_hda_codec         109562  2 snd_hda_codec_realtek,snd_hda_intel
snd_hwdep              13276  1 snd_hda_codec
snd_pcm                80845  2 snd_hda_intel,snd_hda_codec
snd_seq_midi           13132  0 
snd_rawmidi            25424  1 snd_seq_midi
snd_seq_midi_event     14475  1 snd_seq_midi
snd_seq                51567  2 snd_seq_midi,snd_seq_midi_event
snd_timer              28931  2 snd_pcm,snd_seq
snd_seq_device         14172  3 snd_seq_midi,snd_rawmidi,snd_seq
snd                    62064  21 snd_hda_codec_realtek,snd_hda_intel,snd_hda_codec,snd_hwdep,snd_pcm,snd_rawmidi,snd_seq,snd_timer,snd_seq_device
soundcore              14635  1 snd
snd_page_alloc         14108  2 snd_hda_intel,snd_pcm

pacmd

Welcome to PulseAudio! Use "help" for usage information.
>>> list-cards
1 card(s) available.
    index: 0
    name: <alsa_card.pci-0000_00_05.0>
    driver: <module-alsa-card.c>
    owner module: 4
    properties:
        alsa.card = "0"
        alsa.card_name = "HDA NVidia"
        alsa.long_card_name = "HDA NVidia at 0xfebf4000 irq 22"
        alsa.driver_name = "snd_hda_intel"
        device.bus_path = "pci-0000:00:05.0"
        sysfs.path = "/devices/pci0000:00/0000:00:05.0/sound/card0"
        device.bus = "pci"
        device.vendor.id = "10de"
        device.vendor.name = "NVIDIA Corporation"
        device.product.name = "MCP61 High Definition Audio"
        device.form_factor = "internal"
        device.string = "0"
        device.description = "Built-in Audio"
        module-udev-detect.discovered = "1"
        device.icon_name = "audio-card-pci"
    profiles:
        output:analog-stereo: Analog Stereo Output (priority 6000)
        output:analog-stereo+input:analog-stereo: Analog Stereo Duplex (priority 6060)
        output:analog-surround-40: Analog Surround 4.0 Output (priority 700)
        output:analog-surround-40+input:analog-stereo: Analog Surround 4.0 Output + Analog Stereo Input (priority 760)
        output:analog-surround-41: Analog Surround 4.1 Output (priority 800)
        output:analog-surround-41+input:analog-stereo: Analog Surround 4.1 Output + Analog Stereo Input (priority 860)
        output:analog-surround-50: Analog Surround 5.0 Output (priority 700)
        output:analog-surround-50+input:analog-stereo: Analog Surround 5.0 Output + Analog Stereo Input (priority 760)
        output:analog-surround-51: Analog Surround 5.1 Output (priority 800)
        output:analog-surround-51+input:analog-stereo: Analog Surround 5.1 Output + Analog Stereo Input (priority 860)
        output:analog-surround-71: Analog Surround 7.1 Output (priority 700)
        output:analog-surround-71+input:analog-stereo: Analog Surround 7.1 Output + Analog Stereo Input (priority 760)
        output:iec958-stereo: Digital Stereo (IEC958) Output (priority 5500)
        output:iec958-stereo+input:analog-stereo: Digital Stereo (IEC958) Output + Analog Stereo Input (priority 5560)
        input:analog-stereo: Analog Stereo Input (priority 60)
        off: Off (priority 0)
    active profile: <output:analog-stereo+input:analog-stereo>
    sinks:
        alsa_output.pci-0000_00_05.0.analog-stereo/#4: Built-in Audio Analog Stereo
    sources:
        alsa_input.pci-0000_00_05.0.analog-stereo/#1: Built-in Audio Analog Stereo
        alsa_output.pci-0000_00_05.0.analog-stereo.monitor/#5: Monitor of Built-in Audio Analog Stereo
    ports:
        analog-output: Analog Output (priority 9900, available: unknown)
            properties:

        analog-output-headphones: Headphones (priority 9000, available: unknown)
            properties:

        analog-input-microphone-front: Front Microphone (priority 8500, available: no)
            properties:

        analog-input-microphone-rear: Rear Microphone (priority 8200, available: yes)
            properties:

        analog-input-linein: Line In (priority 8100, available: no)
            properties:

        iec958-stereo-output: Digital Output (S/PDIF) (priority 0, available: unknown)
            properties: