hello,
i have a beagleblack bone device and i have two different cards, one for play sound and one for record , the one for recording is usb when the otherone is pluged in the BBB.
I'm trying to figured out what configuration file to have. For now i have :

pcm.usb
{
type hw
card 1
device 0
}

pcm.internal
{
type hw
card 0
device 0
}

pcm.!default
{
type asym
playback.pcm
{
type plug
slave.pcm "internal"
}
capture.pcm
{
type plug
slave.pcm "usb"
}
}

ctl.!default
{
type asym
playback.pcm
{
type plug
slave.pcm "internal"
}
capture.pcm
{
type plug
slave.pcm "usb"
}
}

but it is not working. If I reload alsa then i cannot open alsamixer anymore( alsamixer work fine if i delete the configuration file ) :

ALSA lib dlmisc.c:254snd1_dlobj_cache_get) Cannot open shared library /usr/lib/arm-linux-gnueabihf/alsa-lib/libasound_module_ctl_asym.so
cannot open mixer: No such device or address

and i cannot play sound :

aplay /usr/share/sounds/alsa/Front_Center.wav
aplay: main:682: audio open error: Device or resource busy

configuration:
debian weezy

cat /proc/asound/pcm
00-00: AIC3X tlv320aic3x-hifi-0 : : playback 1 : capture 1
01-00: USB Audio : USB Audio : capture 1

please help
thanks

The error says you're missing a .so. Maybe use dpkg to figure out why it's missing???