I have bougth a Audio-Technica USB microphone (AT2020USB+)
If I select this microphone in the input device I can’t select a diferent sournd card for the output device.
I must select, the same AT2020USB for the input and the output.
Ardour 4.5 does not have the option to select two devices on the ALSA backend, that was introduced in 4.6 IIRC. Plus it is a good idea to stay close to up to date as well.