Ardour 5.3.0 can't connect to JACK session.


On a Debian / Jessie computer, I once custom-compiled Ardour 5.3.0, and tried a few tests with it, successfully always using the ALSA back-end. But, I had compiled Ardour with JACK support as well.

Much more recently I discovered, that this same version of Ardour, can’t seem to connect to a running JACK server (v2). Further, allowing Ardour to start JACK on this machine is not advisable, because this machine already has PulseAudio installed, which I intend to keep, but which QJackCtl can suspend correctly.

Several other programs - such as QTractor - can use JACK just fine on this machine, for which reason I’m assuming that JACK itself is working.

But when I try to start Ardour with JACK, I get a hung window, the GUI of which is just unresponsive - and parts of which don’t display correctly. Starting Ardour from the command-line this way, produces no error messages.

Do people have any hints for what might b going wrong? I could just continue to use Ardour on this machine, with ALSA, but out of principle, would also like JACK support working.



and to be even more precise: When Ardour uses multi-core processing ( Preferences > General > CPU Utilization) with more than 1 CPU, ardour asks jackd to start realtime-process threads.
If jackd has no permissions to create those, it’ll fail.

Re-configure your user and take away the rt-permissions, and configure ardour to use > 1 CPU (default is “all but one”). It should fail even if you start jackd without rt-permissions.

to be more precise: if Ardour starts JACK, then it forces the use of the “run with realtime scheduling priority” flag.

That explains it.

No problem running Ardour 5.12 and jack1 without realtime here :

/usr/local/bin/jackd -r -dalsa -r48000 -p1024 -n2 -D -Chw:PCH,0 -Phw:PCH,0
jackd 0.125.0

Ardour Config :
ALSA Backend: True
Dummy backend: True
JACK Backend: True

From ardour’s point of view there is no difference between jack1 and jack2 – jack1 is actually newer than jack2. I’ve been using Ardour 2 more than a decade ago with jack2/jackdbus already.

However recent Ardour requires jackd to be running with realtime permissions.

I suspect the problem was perhaps missing or invalid realtime setup. Debian/Ubuntu sets this up automatically when you install jack, but you do need to re-login for the change to be effective. – see step 3 at for details.

Have fun!

Actually, what I just did was:

To custom-compile Ardour 5.12, with ALSA as well as JACK support. And what I found, was that it works fine in both modes, for each of which I did set up a test project.

What I suspect is that v5.3 still did not have support for ‘jackd2’, while up-to-date Ardour does.

Strangely, the version that comes from the package-manager, for Debian / Stretch (9), is still only v5.5 . Yet, this distro-version, also works, both in ALSA and in JACK mode.

Thank you!


5.3 is considered out of date. The current release is 5.12. In addition, we cannot support self-builds or Linux distribution builds because of the many factors that can results in a broken program.

Please at least try out the free/demo version of 5.12 available at to confirm that this works.