An Audio Input Under Linux Success Story, a Long Time in Coming

Since I started using Linux seven years ago, I've never been able to make a microphone work, although I've wanted to. I've never been able to record sound or use any nifty applications that require audio input from me. That is, until now. Here's how I got things to work, for my particular little hardware corner-case. Like any other good Linux success story, this one took a lot of hard work and patience to achieve.

First, here's my setup. The box-of-success is a Slackware 10 box running Linux kernel 2.6.12.2, with Alsa 1.0.9rc2. Here's the output of cat /proc/asound/cards:

0 [CS46xx         ]: CS46xx - Sound Fusion CS46xx
                     Sound Fusion CS46xx at 0xcfffd000/0xcfe00000, irq 12
1 [SI7012         ]: ICH - SiS SI7012
                     SiS SI7012 with CMI9738 at 0xdc00, irq 10

The card with which I've been working is the one using the cs46xx driver. To weave the magic, we'll be using alsamixer, which I ran as root. You may want to use alsamixer -V all in order to see all the options at once. For me, the trick was understanding that there are three independent actions you can take on the various items in this display. (I was previously only aware of two.) You can mute or unmute various items (with the "M" key), you can change the volume on various items (with the up and down arrows), and you can activate capture on various items (with the space bar). It is this third type of action that escaped me for so long.

Now plug in your microphone correctly, physically unmute that microphone (if it has such a capability—many modern headsets do), and bring up the alsamixer interface. These are the settings that were critical for me.

• External Amplifier - unmuted

• DAC - activate capture, change the volume to a comfortable level

• ADC - activate capture, change the volume to a comfortable level

• Capture corresponding to desired mic - activate capture, change the volume to a comfortable level

• IEC958, IEC958 Input, IEC958 Output - muted seems better than unmuted, although both work

• Appropriate Mic - unmuted, activate capture, change the volume to a comfortable level

• Mic boost corresponding to appropriate Mic - either muted or unmuted

• Everything else unmuted, with the volume turned up (although I did not do a thorough test of every other option)

Mad respef to gnubien in #alsa on irc.freenode.net for being patient with me for over two hours to get it working. I also found the Alsa bugtracking system useful for seeing what other people were trying (in my case, report 1605).