How can I access the external microphone with Ubuntu?

Question

Sound in Ubuntu, it has its own special joy. I would like my external microphone to work.

Symptoms:

• I can play sound through the speakers
• I can play sound through the headsets.
• Plugging and and plugging headphone output correctly switches.
• I can record from the built-in microphone, using "Sound Recorder" and others.

but:

• I cannot record from the external microphone.
• My Sound Preferences/Input panel has no option for an external microphone.

If the answer is upgrade the ALSA drivers, please say exactly what to type.

Thank you.

========

I'm using Ubuntu 9.10 Karmic Koala on a laptop (Gateway W3501), Sigmatel.

That is:

~$ head -1 /proc/asound/card0/code*
==> /proc/asound/card0/codec#0 <==
Codec: SigmaTel STAC9205

==> /proc/asound/card0/codec#1 <==
Codec: Conexant ID 2c06
~$ lspci | grep -i audio
00:1b.0 Audio device: Intel Corporation 82801H (ICH8 Family) HD Audio Controller (rev 03)

Solution

First, I looked at the ALSA website, because the sound drivers ship out of sync with the usual Ubuntu upgrades. For Intel HDA especially, the recommendation is to install alsamixer and then go playing with settings.

$ sudo apt-get install alsamixer
$ alsamixer

Then I found that the default settings for "Digital Input Source" is incorrect. It should be "Analog".

Comments

[Csaba Toth]

Where do you see "Digital Input Source" in alsamixer? I'm running v 1.1.3, when I start it the default sound card has one master and one capture potentiometer. When I select the sound card HD Audio Generic which is a Realtek ALC256, then I see two separate Mic Boost potentiometers and when I adjust one the other follows as well. But I don't see where to select the input source and I cannot access my external mic. This is an ASCII graphic program just to be clear.