Ralf, here is the output from dpkg:
i jack-capture 0.9.71-1 amd64 program for recording soundfiles with jack
ii jackass 1:20140520-1kxstudio1 amd64 JACK-MIDI support for VST hosts
ii jackd 5 all JACK Audio Connection Kit (default server package)
ii jackd1 2:0.124.2~20151211-2~xenial1 amd64 JACK Audio Connection Kit (server and example clients)
ii jackd1-firewire 2:0.124.2~20151211-2~xenial1 amd64 JACK Audio Connection Kit (FFADO backend)
ii jackutils-script 0.0.1avlinux6-1 all Simple Start and Stop Scripts to Utilize With QJackctl and Launch a2jmidid and aloop-daemon - Custom AV Linux Package
ii libjack-dev 2:0.124.2~20151211-2~xenial1 amd64 JACK Audio Connection Kit (development files)
ii libjack0:amd64 2:0.124.2~20151211-2~xenial1 amd64 JACK Audio Connection Kit (libraries)
ii libjack0:i386 2:0.124.2~20151211-2~xenial1 i386 JACK Audio Connection Kit (libraries)
ii qjackctl 2:0.4.1-1kxstudio2 amd64 User interface for controlling the JACK sound server
ii screencapjack-script 0.1.2avlinux8-1 all A very basic screen capture script using ffmpeg and jack-capture, the script is installed to /usr/local/bin and can edited with a text editor. Custom AV Linux Package
I am using buffer size 128, N=3, 48000hz. When I use N=2, all I hear is some clicking. I don't currently have an external instrument or tuning fork. I think the latency problem may be due to the above - seems I installed things from kxstudio that I didn't realize. I'm not sure why I can't use an even smaller buffer size; I guess pianoteq is too cpu intensive.
When I take jack out of the equation and play an mp3 file thru ecasound and the 2-way crossover, it works correctly and sounds good.
By the way, I'm embarrassed to admit that I really have forgotten my admin password, so I think I need to re-install AVL. That would get me back to the correct baseline for Jack in AVL. But then I would have to decide whether to re-install ecasound - which might have been what corrupted jack for me?? Or, to forget ecasound and use zita-Irc.
Thanks,
John