[LAU] JACK and S/PDIF sync'ed delta 1010 cards: bad vs. evil?

[Jeanette C.]

Hey hey,
I have two M-Audio Delta 1010LT cards, sync'ed via S/PDIF. Two ALSA devices 
were created to sum the inputs and outputs respectively.

On top of that JACK is running. Now, I noticed that it is a decision between 
two problems that I face: if they are correctly sync'ed, some system services 
regularly freeze. This includes the networ, the Braille display (connected via 
USB). If, as has happened before, the setup isn't remembered correctly and the 
S/PDIF sync is not made, occasionally the cards begin to have input problems. 
The sound suddenly degrades with an effect like bad resampling (decimation 
effect).

I have had these cards running for a long time in this constellation, but only 
in the past few years these problems cropped up. I have changed the distro 
from Debian to Arch Linux. On Arch I have tested the system for realtime 
operation several times, using the realTimeConfigQuickScan script.

Could this be a kernel issues? Some ALSA update? Or a question of the kernel 
patches that one is running? I am running the following two kernels now:
5.6.19-rt12-1-rt
or
5.8.14-arch1-1

The last time I ran Debian it was on a 2.6.3x kernel, IIRC.

Any suggestions, apart from don't use your cards at once, would be very much 
appreciated. :)

Best wishes,

Jeanette

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