Ardour shows only 2 physical out channels instead of 6 (Surround 5.1)


my Ardour is showig only 2 physical output sinks in the master section connection matrix, instead of 6.

As I created the project, I selected PulseAudio and my HDMI Surround 5.1 output device and I adjusted the number of master channels to 6.

I can see 6 VU meters in the master section and 6 Out-Channels of the Master but only 2 physical sinks.

When I add a 6 channel OGG file as input, I can also see that all master VU’s are moving.

What am I doing wrong?

My best regards, Matthias