How can I replace PulseAudio with Jack? I want to start jackd on startup either during boot or during logon instead of PulseAudio.
You can add it to your start-up applications but maybe that's not very good idea as not all audio applications support jack. To make things easier there exist programs for managing and starting jack, and I think that is recommended way to use it. At least untill you get familiar with jack, and don't need assistance
So instead just launching it on start-up you could install
You don't need to replace pulseaudio. You can configure pulseaudio to redirect everything to jack. With his method, all applications which use pulse continue to work. At least this is what works for me on 12.10: Running PulseAudio on top of JACK
In section 'Redirecting PulseAudio to JACK'
After installing the necessary pulseaudio module
I performed the following changes to the files in /etc/pulse:
Hope this helps