I have a problem with Jack Audio Connection Kit and ALSA driver. I use qjackctl to run jack. When I start jack server with the ALSA driver, it doesen't work. I plug (in the qjackctl window) e.g. my microphone input into output, but I don't listen anythink. Other strange think is, that it detects many outputs of the soundcard. I have onboard soundkard wiht just 1 stereo output. On the other hand I think, the ALSA driver works. E.g. skype uses it.
When I use OSS driver instead of ALSA, jack server works well. But I prefere ALSA.
I use FC6 and planetCCRMA.
Perhaps I didn't write enough information. Pleas ask me, if so. Than you.

Use the alsa-plugins package (it is called this way on gentoo, and perhaps also on Fedora.)

Uninstall OSS. You really don't need it (in the gentoo kernel it is set as deprecated)

Be sure alsa is started.

Try to start the jackd server on the command line and look what the error is.
Same for your audio application.

Are you sure your volume levels are not muted? If you use alsa, use the alsamixer tool

Thank you for your answer. Well I think, that alsa is running. I can record with aslsa in audacity. But I can't find this file /etc/rc.d/init.d/alsasound, which I think could be present. How can I check, whether is alsa started? I can't find alsa-plugins in fedora repository. I think alsa is part of planetCCRMA kernel, so I shouldn't have to install anything. When jack is running from command line, it doesn't give any error message, but doesn't work.

My soundcard is C-Media CM8738

this is hard to diagnose with the information given.
this statement is confusing so explain exactly what steps you are taking to use OSS driver or ALSA driver.
it's hard to imagine you are actually using a different sound card driver so there must be some confusion about that.

You can choose driver in qjackctl setup. There are several drivers offered. With OSS it works, with ALSA jack server starts, but doesen't work. When I try to use other drivers, jack server wouldn't even start.
I'm sory for incomplete information, I'm beginer in this topic. Pleas ask me again for some more detailed information.

I set number of input chanels to 2, number of outputchanels also 2 and it work's now. By default it was set to 0. Thank you for help.

Glad you could fix your problem!
Aren't you proud now?

Well, I'm not. It is quite obvious, that I should set 2 inputs, when i have 2 inputs . And I spent much time on it.
Now, I have another problem. Jackserver makes the sound noisy, as it is over-excited (not shure about the correct english word, I mean the sound when signal is too loud so that the input can't manage it.) But this noise appear even when I make the volume on preamp very silent. It's shurely problem of jackserver. When I stop jackserver and let playback microphone on alsamixer, it sounds well. Do you have some idea, what I could try to solve this?

Now, it works. There was some problem with the output of the preamp.
Thanks

I'm sorry, it doesn't work, I just thought it works. It still sounds bad. Does anyone know, how to fix it?

Could anyone help, please?