Eric,
In the mean time I have tried the following: I switched off Roon and put the url http://icecast.vrtcdn.be/klara-high.mp3 directly on the Safari of my MacMini. With that setup the streaming to the Cord 2Qute DAC is perfect again. As soon as I try the same with Roon, the problem of pulsing noise and bad quality is back again.
I also contacted Widescreen Audio, who actually gave me the tip to try the above setup. Can they also be informed at henk@widescreenaudio.be?
What can I do from here on?
Roger