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Hi. I am running debian sid on a Compal IFL90. It has a Realtek ALC268 sound card. I configured ALSA with options snd-hda-intel model=toshiba in /etc/modprobe.d/alsa-base. The sound output works ...
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  1. #1
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    DC offset when recording audio with Realtek ALC268


    Hi. I am running debian sid on a Compal IFL90. It has a Realtek ALC268 sound card. I configured ALSA with options snd-hda-intel model=toshiba in /etc/modprobe.d/alsa-base. The sound output works fine, but when recording, there is a significant DC offset from both the built-in mics and the mic jack even when nothing is plugged in. The offset increases when the capture volume and mic boost is increased, so I cannot record with very much volume before the sound is clipped. This makes the built-in mics useless, because the capture volume must be turned up very high. Is this a hardware problem in my sound card, or is it an issue with the software, and can I fix it?

  2. #2
    Linux Engineer aliov's Avatar
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    consider reporting a bug to ALSA, attach lspci -vv and your Distro with the kernel version, i did for my sound card, the snd-hda module seems to be buggy, meanwhile to you try to boot your system with the option acpi=off, my sound works only with this option in a kernel version less than 2.6.25 ( only 2.6.25 makes my sound card works perfectly).
    Linux is not only an operating system, it's a philosophy.
    Archost.

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    Thanks. I'll try kernel 2.6.25 and see what happens.

    $ uname -rvmo
    2.6.24-1-686 #1 SMP Sat Apr 19 00:37:55 UTC 2008 i686 GNU/Linux

    lspci -vv output is attached
    Attached Files Attached Files

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    Linux Engineer aliov's Avatar
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    consider sending these information to https://bugtrack.alsa-project.org/al...login_page.php

    regards.
    Linux is not only an operating system, it's a philosophy.
    Archost.

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    I sent the information in. It is number 3930
    I haven't been able to run 2.6.25 yet, I get a kernel panic and I haven't had time to fix it because last week was finals week. Now that I have some more time I will get on that.

  7. #6
    Linux Engineer aliov's Avatar
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    A kernel panic is expected when you switch your kernel, wish distro you are using, see how you can build the initrd or the initramfs for your distro (contains at least your file system module).
    Linux is not only an operating system, it's a philosophy.
    Archost.

  8. #7
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    I just got kernel 2.6.25.2 up and running and tested the sound. It works the same as it did before. The offset has not changed.

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