I've been having problems in getting my microphone input to work. Frustratingly, it works sometimes and doesn't work at other times, and I have yet to discover what causes the difference. I've been testing it with the Skype Sound Test Service.

My laptop, like most others, has a built-in microphone as well as a microphone jack (which I'm using). In kmix, there are sliders for:
Mic
Mic Boost
Mic Boost (Capture)
Capture
Capture 2
What do all of these do, and how do they relate to the two microphone sources? Can I use them to select input from one source while silencing the other? Where can I read about this?

I'm running Kubuntu Koala, so I asked this question over in the Kubuntu forum, but no one there has responded. That was probably not the best place to try (for this issue, at least).

Hmm - have you tried opening a console and running

?

I've had a similar problem on my FC11 desktop system, where these sliders your mention (Mic specifically) did nothing at all. I had to go into ALSA mixer and set them there, and only then the sound card (an old SB Live 5.1) responded correctly.

AFAIK Mic refers to microphone input volumne, Mic Boost to how much to boost microphone output. Strange, in my ALSA mixer screen, Mic boost is a TOGGLE, not a slider? I also don't know why you have a Mic Boost and a Mic Boost (capture) - by definition, a microphone -captures-, not so? Strange.

I think Capture 1 and Capture 2 might refer to a line in input your sound hardware might be capable of.

Also take note with laptops / netbooks, you -might- sometimes get one that has generic hardware (that your sound driver may recognise) but that not all the outputs or inputs might physically be present. I. e. you might have a lower specced model of a certain line of laptops or netbooks, which does not necessarily have all the physical RCA jacks on the casing for all of the sound system's functions, even though the controlling chip does support them, and they are thus detected by any driver you might load... even though you can't use them because they aren't physically accessible on the system chassis.

I tried using Alsamixer, but I still couldn't learn anything. I did discover that the F1 key in Alsamixer brings up help, and through that learned how to switch the view mode to All (use the tab key). Alsamixer displays two mysterious controls, IEC 958 and IEC 958 D. I have no idea what they do.

The fundamental problem I'm facing is that when the behavior appears to be inconsistent, it's hard to determine whether a particular action has helped or not.

If you ever discover documentation on what all these controls mean, not just how to manipulate them, please post that information.

Thanks for your help.