2.3.1. Install and Configure JACK
Use PackageKit or KPackageKit to install the jack-audio-connection-kit and qjackctl packages.
Review and approve the installation, making sure that it completes correctly.
Run QjackCtl from the KMenu or the Applications menu.
To start the JACK server click Start. To stop the JACK server click Stop.
Click Messages to see messages, which are usually errors or warnings.
Click Status to see various statistics about the currently-running server.
Click Connections button to see and adjust the connections between applications and audio hardware.
Important
JACK operates with special real-time privileges. You must add all JACK users to the jackuser group. Learn how to add users to groups in Chapter 22, Users and Groups of the Fedora Deployment Guide, available at http://docs.fedoraproject.org. Do not add a user to the jackuser group if they will not use JACK.
By default, QjackCtl configures JACK to use the 'default' sound card. The 'default' sound card uses all features of the ALSA driver even though JACK provides the same features. To save memory and processor time, you should configure QjackCtl with a specific sound card.
Open a terminal. In GNOME, choose Applications → System → Terminal. In KDE, click on the application launcher, then choose System → Konsole.
Execute this command: cat /proc/asound/cards
The cat program outputs a list of sound cards in your computer that looks similarly to this:
0 [SB             ]: HDA-Intel - HDA ATI SB
                  HDA ATI SB at 0xf7ff4000 irq 16
1 [MobilePre      ]: USB-Audio - MobilePre
                  M Audio MobilePre at usb-0000:00:13.0-2
In this example output, the square brackets surround the name of the sound card. The names of the sound cards in this example output are SB and MobilePre.
Identify the name of the sound card that you want to use. If you do not see your sound card in the list outputted by cat then your computer does not detect it.
Start QjackCtl.
Click Setup to open the "Setup" window.
In the 'Interface' text box type the name of your preferred sound card with "hw:" in front. With the sound cards listed above you might write hw:MobilePre.
Save your settings by exiting QjackCtl. If you want to use JACK, restart QjackCtl.