Ubuntu 13.10.

The problem is: the internal speakers don't work. I have no problem when I'm using the headphones. There is no hardware issue since in windows 8 everything works perfectly(external subwoofer included).

I'm trying to modify /etc/modprobe.d/alsa-base.conf but I can't find the correct model to put into:

 options snd-hda-intel model=

The file HD-Audio-Models.txt doesn't contain the model for ALC668.

Some info:

:~sudo aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: MID [HDA Intel MID], device 3: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: MID [HDA Intel MID], device 7: HDMI 1 [HDMI 1]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: MID [HDA Intel MID], device 8: HDMI 2 [HDMI 2]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: PCH [HDA Intel PCH], device 0: ALC668 Analog [ALC668 Analog]
  Subdevices: 0/1
  Subdevice #0: subdevice #0

:~$ sudo lspci -v | grep -A7 -i "audio"
00:03.0 Audio device: Intel Corporation Xeon E3-1200 v3/4th Gen Core Processor HD Audio Controller (rev 06)
    Subsystem: Intel Corporation Device 2010
    Flags: bus master, fast devsel, latency 0, IRQ 52
    Memory at f7a14000 (64-bit, non-prefetchable) [size=16K]
    Capabilities: [50] Power Management version 2
    Capabilities: [60] MSI: Enable+ Count=1/1 Maskable- 64bit-
    Capabilities: [70] Express Root Complex Integrated Endpoint, MSI 00
    Kernel driver in use: snd_hda_intel
--
00:1b.0 Audio device: Intel Corporation 8 Series/C220 Series Chipset High Definition Audio Controller (rev 04)
    Subsystem: ASUSTeK Computer Inc. Device 11cd
    Flags: bus master, fast devsel, latency 0, IRQ 53
    Memory at f7a10000 (64-bit, non-prefetchable) [size=16K]
    Capabilities: [50] Power Management version 2
    Capabilities: [60] MSI: Enable+ Count=1/1 Maskable- 64bit+
    Capabilities: [70] Express Root Complex Integrated Endpoint, MSI 00
    Capabilities: [100] Virtual Channel

PS info

:~$ amixer -c 0
Simple mixer control 'IEC958',0
  Capabilities: pswitch pswitch-joined
  Playback channels: Mono
  Mono: Playback [on]
Simple mixer control 'IEC958',1
  Capabilities: pswitch pswitch-joined
  Playback channels: Mono
  Mono: Playback [on]
Simple mixer control 'IEC958',2
  Capabilities: pswitch pswitch-joined
  Playback channels: Mono
  Mono: Playback [on]

:~$ pacmd dump-volumes
Welcome to PulseAudio! Use "help" for usage information.
>>> Sink 0: reference = 0:  76% 1:  76%, real = 0:  76% 1:  76%, soft = 0: 100% 1: 100%, current_hw = 0:  76% 1:  76%, save = yes
    Input 8: volume = 0: 100% 1: 100%, reference_ratio = 0: 100% 1: 100%, real_ratio = 0: 100% 1: 100%, soft = 0: 100% 1: 100%, volume_factor = 0: 100% 1: 100%, volume_factor_sink = 0: 100% 1: 100%, save = no
Source 0: reference = 0: 100% 1: 100%, real = 0: 100% 1: 100%, soft = 0: 100% 1: 100%, current_hw = 0: 100% 1: 100%, save = no
Source 1: reference = 0:  16% 1:  16%, real = 0:  16% 1:  16%, soft = 0: 100% 1: 100%, current_hw = 0:  16% 1:  16%, save = yes