I ALSA Don't know JACK about linux-rt kernel
Okay, I thought I would quickly document the exact procedure to get JACK (via QJackCtl GUI) to play nice with ALSA and the Real-Time kernel (linux-rt) on Ubuntu 9.10.
1. Install linux-rt from synaptic
2. Install QJackCtl from synaptic or Ubuntu Software Store
3. Go to System -> Administration -> Users & Groups and add your user to the following groups: audio, pulse, pulse-access
4. Enter the following into your command line
> sudo su -c 'echo @audio - rtprio 99 >> /etc/security/limits.conf'
6. Start QJackCtl and edit the following prefs:
Setup -> Settings tab: check the boxes next to Realtime and No Memory Lock
Setup -> Misc. tab: check the box next to Start Jack Server on Application Start-up.
7. Restart QJackCtl and voila!