[LAU] [solved] Focusrite 18i20 balanced -> unbalanced

Hi, I don't know what solved the issue, but actually the output sound is ok. It's still not in the same class as RME, but from good hifi quality. For the cable plugged into channel 2 of the Focusrite only tip and sleeve are soldered. For the cable plugged into channel 1 of the Focusrite only tip and sleeve are soldered, too, but by a crocodile clip cable I connected and disconnected ring with sleeve [1]. There's neither a difference in volume, nor in tone, with ring and sleeve short circuit or not. A big surprise was, that comparing the output of the Focusrite, with the output of a CD player, everything was ok yesterday, when the testing was done. I couldn't reproduce the bad sound I experienced before. The output level of the Focusrite was ok as well. No other analog audio cables were connected to the other channels. Perhaps some of the other audio cables, connected to other outputs caused problems by the tests, I made a while ago. However, this morning I checked channels 3, 5, 7 and 9 against channel 2, again with a short circuit and without it and after that I compared channels 4, 6, 8 and 10 with channel 9, but only without a short circuit. And finally I repeated to compare channel 1 and 2 with a CD player. Everything sounded very well. With linux 4.9.0-rt1 it's possible to go down to 32 frames at 48 KHz, getting lots of inaudible xruns, at 16 frames as well as 64 frames the interface is completely unusable. At 128 frames it's the same as for a vanilla kernel with threadirqs, just scrolling with the USB mouse wheel in roxterm usually does cause issues, very seldom a random xrun could happen, when switching to another window. At 256 frames it seems to be absolutely stable, however, it seems to be usable at 128 frames, with linux-rt as well as a vanilla linux with threadirqs. FWIW using another USB cable at 128 frames doesn't make a difference. Actually it even seems to be usable at 32 frames, the xruns were inaudible. I don't know why it's completely broken at 64 frames. 16 and 64 frames cause long interrupted audio signals. Regards, Ralf [1] http://picpaste.com/pics/IMG_2250_unbalanced.1484895640.jpg