If, like me, you have the same module loaded for your onboard sound as for your Nvidia HDMI and only want to use the onboard ever, here's a little command I wrote that could help you:
Copy and paste the output of that before the "exit 0" in your /etc/rc.local and enjoy not having to mess about with mixer settings etc.
Code:
find /sys/devices -name *`lspci | grep Audio | awk /NVIDIA/{'print $1'}` -exec echo "echo 1 > {}/remove" \;