Rpi usb 5.1 external card doesn't work - asound.conf

I’ve a RPI with an external usb 5.1 surround card connected and with volumio installed. It works, but only the front speakers are connected. Before volumio I had rasbian installed with an modified asound.conf.
It must be possible to modify asound.conf with volumio, but I can’t get it right.
The working asound.conf (with only the front speakers) is:
pcm.softvolume {
type plug
slave.pm “softvol”
}

pcm.softvol {
type softvol
slave {
pcm “plughw:5.0”
}

control {
name “Softmaster”
card 5
device 0
}

max_db 0.0
min_db -50.0
resolution 100
}

Somewhere I’ve to add:
pcm.route_2_to_5_1 {
type plug
slave.channels 6
ttable.0.0 1
ttable.1.1 1
ttable.0.2 1
ttable.1.3 1
ttable.0.4 1
ttable.1.5 1
}

but I can’t figure out a working version. Can somebody please help me with this???

Thanks,

Paul