Topic: ALSA output not working properly on RME RayDat

I'm trying to play output sound on my Linux Gentoo with ALSA to RME RayDat sound intereface. The configuration file is

    pcm.mixer {
            type dmix
            ipc_key 10000
            ipc_key_add_uid true
            ipc_perm 0666
            slave {
                    pcm "hw:2,0"
                    format S32_LE
                    rate 48000
                    period_time 10666
                    channels 36
    pcm.device_out { 
            type plug
            slave.pcm mixer
            ttable {
                    0 { 0 1 }

I can hear output but the sound is not continuous. And the weird thing is, that input device (dsnoop type) set up with the same parameters is working without any problem.

Is there anyone experienced with setting up ALSA working with RME RayDat or other external sound device?

Note: When I send the output to the device type "route", it works, but type "dmix" is a problem. And I need to mix multiple streams together.