HDMI passthrough + USB DAC

[ziopanna]

Hi guys,
I've read a lot of thread regarding multiple audio output on XBMC etc. but I didn't find what I'm looking for.

I've a double audio setup. One with a multichannel AVR and another one with USB DAC connect to an hi-end 2.0 HiFi

I've tried to setup my new Raspberry Pi 2 with Xbian to match this type of configuration but unfortunately everything works fine only with HDMI connection.
I tried to change settings in Audio section putting ALSA: Musical Fidelity Analog in the main section and HDMI in device passthrough. With this configuration Films and other contents with multiple channel audio works fine but I can't listen any songs. In the HiFi system I can hear only noise.
I also read that XBMC does't support ALSA but why I can select it?

Is there someone who can help me with this?

Sorry for my poor English, I'm Italian

Best regards.
Luca