MSI GX740 - Intel 5/3400 - ALC888 : no sound on right speaker

[adrenochrome]

The computer used is a MSI GX740
lspci report :
00:1b.0 Audio device: Intel Corporation 5 Series/3400 Series Chipset High Definition Audio (rev 05)
cat /proc/asound/card*/codec\#*|grep -i codec :
Codec: Realtek ALC888
Codec: LSI ID 1040
Codec: ATI R6xx HDMI

I get sound from left speaker and subwoofer but nothing on right speaker
If i plug a headphone, stereo is ok and reacting as expected when playing withbalance control

i tried model tweaking through alsa-base.conf
3stack-hp,3stack-6ch-intel,3stack-2ch-dig,3stack-6ch,3stack-dig,laptop-eapd,targa-dig,targa-8ch-dig
but i only managed to get worst results with these settings

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: alsa-base 1.0.24+dfsg-0ubuntu1
ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2
Uname: Linux 2.6.38-8-generic x86_64
NonfreeKernelModules: fglrx
AlsaVersion:
 Advanced Linux Sound Architecture Driver Version 1.0.24.
 Compiled on Jun 13 2011 for kernel 2.6.38-8-generic (SMP).
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: adrenochrome 1511 F.... pulseaudio
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xd6600000 irq 43'
   Mixer name : 'Realtek ALC888'
   Components : 'HDA:10ec0888,1462100f,00100202 HDA:11c11040,11c10001,00100200'
   Controls : 29
   Simple ctrls : 16
Card1.Amixer.info:
 Card hw:1 'Generic'/'HD-Audio Generic at 0xd0040000 irq 44'
   Mixer name : 'ATI R6xx HDMI'
   Components : 'HDA:1002aa01,00aa0100,00100200'
   Controls : 4
   Simple ctrls : 1
Card1.Amixer.values:
 Simple mixer control 'IEC958',0
   Capabilities: pswitch pswitch-joined penum
   Playback channels: Mono
   Mono: Playback [on]
Date: Mon Jun 13 15:33:43 2011
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=fr_FR:en
 LANG=fr_FR.UTF-8
 SHELL=/bin/bash
SourcePackage: alsa-driver
UpgradeStatus: Upgraded to natty on 2011-05-04 (39 days ago)
dmi.bios.date: 10/12/2010
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: E1727IMS.10C
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: MS-1727
dmi.board.vendor: MICRO-STAR INTERNATIONAL CO., LTD
dmi.board.version: REV:1.0
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: MICRO-STAR INTERNATIONAL CO., LTD
dmi.chassis.version: N/A
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrE1727IMS.10C:bd10/12/2010:svnMICRO-STARINTERNATIONALCO.,LTD:pnMS-1727:pvrREV1.0:rvnMICRO-STARINTERNATIONALCO.,LTD:rnMS-1727:rvrREV1.0:cvnMICRO-STARINTERNATIONALCO.,LTD:ct10:cvrN/A:
dmi.product.name: MS-1727
dmi.product.version: REV:1.0
dmi.sys.vendor: MICRO-STAR INTERNATIONAL CO., LTD

[adrenochrome (adrenochrome)]

found a solution, i used the settings advised here : http://www.backtrack-linux.org/forums/backtrack-5-beginners-section/41508-alsa-problem-after-successful-update.html

options snd-hda-intel index=0 model=acer-aspire-7730g

now, for the first time i have subwoofer, left and right speaker, all working at the same time :)
as positive side effet, volume never was so loud