Right, so now to bring this thread to a usefull conclusion.
I'm new to Linux but as a Beta tester from the early days of Samplitude (what's that? ) I new there are many reasons leading to apparent problems.
I had tested all variations I could think of except one:
I loaded Ardour with Pianoteq and tried both interfaces with ALSA alone and also with Jack.
Lovely GUI BTW - Ardour is a pleasure to work with.
I managed to crash Ardour once which made it fold up without freezing the whole system.
Apart from that, Ardour was rock solid.
Shame it uses so much CPU, one instance of Pianoteq runs between 65% and 95%
In Reaper 18% to 25%
I wrote about this on the Reaper Linux forum and found someone who had the same problem with ALSA Midi.
He too found that Jack2 somehow bypasses the problem.
So for anyone looking for a top quality multitrack interface on a budget, I can highly recommend:
Motu Traveler Mk1 - with ADAT up to 20 simultaneous inputs.
Motu Traveler Mk3 - with ADAT up to 28 simultaneous inputs.
https://www.musicradar.com/reviews/tech ... mk3-215586
The Terratec Phase 24 is probably not known so much outside of Europe, but it won so many tests back in its day for its converters and pro headphone amplifier.
Works great in Linux.
Thanks for your interest.