Some Joy with JACK

One of the mysteries of Ubuntu is why there is no underlying audio production infrastructure. Linux users have long suffered because of the disregard for music production. Most Linux music production apps rely on JACK to port sound. If you want to use JACK, you'll have to install the ubuntustudio-audio package. Doing this any other way will lead to partially configured packages. Still it is not the easiest of solutions, and hopefully some day the entire Ubuntu sound infrastructure will receive a more user-friendly overhaul.,

In order to get the most out of JACK, you will want the lowest possible latency. It can be a daunting task at first, because there are a lot of settings and if you change them a certain way, you can cause the server to not start up properly.

Firstly, you will want Real-Time capabilities; either install the ubuntustudio-audio package, or read through theUbuntuStudioPreparation page for help on getting your studio set up properly.

Now, open up QjackCtl, and change the settings in here. Generally, to get the lowest latency, you're mostly concerned with the Frames/Period, Sample Rate, and Periods/Buffer settings.

https://help.ubuntu.com/community/HowToJACKConfiguration