@DavidMc: You might have already tried this, but maybe not: I don’t start Jack via qjackctrl; this did not work for me a while ago (never found out why) and so I created a - very simple - script called jack-internal, which I run. (Additionally I have an external audio device which, if pluged in, I trigger with another audio start script.)
It looks something like that for my internal soundcard:
#! /bin/bash
pulseaudio --kill &
jackd -d alsa --device hw:0 --rate 44100 --period 1024 & # internal soundcard
sleep 3
qjackctl --start &
This is called by another script e. g. audio-internal-sonicpi, which I adjust according to what I need. E. g.:
#! /bin/bash
pulseaudio --kill &
jack-internal &
sleep 1
a2jmidi_bridge &
sleep 1
sonicpi &
# start some softsynth or other things ...
Accordingly I do also have a stop script audio.stop to restart pulse-audio and quit Sonic Pi and other things:
#! /bin/bash
killall -9 sonicpi sonic-pi m2o o2m beam.smp ruby &
killall -9 qjackctl &
killall -9 carla &
#killall -9 helm &
sleep 3
exit
This can surely be done much more elegantly and more profoundly but so far it is a working and practical solution.
