Dual output? USB audio card and HDMI?

Is it possible? Ie have an USB card for 5.1 and still have audio over HDMI?

I imagine it is possible but only if you get down and dirty with ALSA config files. Then it’s unlikely the two signals will be in phase (if you are trying to drive different channels in the same room, as I suspect you are).

Yes. I guess I would run into latency problems.

Testing this:

pcm.both {
    type route;
    slave.pcm {
        type multi;
        slaves.a.pcm "plughw:0,0"
        slaves.b.pcm "plughw:1,0"
        slaves.a.channels 2;
        slaves.b.channels 6;
        bindings.0.slave a;
        bindings.0.channel 0;
        bindings.1.slave a;
        bindings.1.channel 1;
        bindings.2.slave b;
        bindings.2.channel 0;
        bindings.3.slave b;
        bindings.3.channel 1;
        bindings.4.slave b;
        bindings.4.channel 4;
        bindings.5.slave b;
        bindings.5.channel 5;
        bindings.6.slave b;
        bindings.6.channel 2;
        bindings.7.slave b;
        bindings.7.channel 3;
    ttable.0.0 1;
    ttable.1.1 1;
    ttable.0.2 1;  
    ttable.1.3 1;  
    ttable.2.4 1; 
    ttable.3.5 1; 
    ttable.4.6 1; 
    ttable.5.7 1; 

pcm.test {
        type plug
        slave.pcm "both"

ctl.test {
        type hw
        card SB