if kernel does not include PREEMPT try this,
$ sudo apt-get install linux-lowlatency
not sure if that will fix it in ubuntu, but your goal is to have a low latency kernel
also, you should start reading about kernels and this fellows guide. perhaps sending him emails will help.
but he did mention this,
Note: Ubuntu/Debian can set up a properly configured audio group for you when you install jackd2. If you'd like, you can do this before continuing:
$ sudo apt-get install jackd2
have you done that yet?
$ sudo apt-get install linux-lowlatency
not sure if that will fix it in ubuntu, but your goal is to have a low latency kernel
also, you should start reading about kernels and this fellows guide. perhaps sending him emails will help.
but he did mention this,
Note: Ubuntu/Debian can set up a properly configured audio group for you when you install jackd2. If you'd like, you can do this before continuing:
$ sudo apt-get install jackd2
have you done that yet?