System up time has been up about 5 hours and sound was working fine in my windows 10 vm. Restarting the guest vm causes sound to stop working. The only way to get it back is to reboot the host. I have tested this several times now and the behaviour is consistent.

 

Edit: I have attached the vm log and system log after a vm reboot when I have lost sound.

tower-syslog-20160429-1940.zip

Added devices / iommu info.

Further testing has revealed that the onboard sound can be restored after a reboot by going to device manager and finding the device, disabling it and re-enabling it. This is a little bit annoying  but at least it works! Hope this is helpful for anybody else running into this issue.

 

Now to sort out why my wireless xbox controller is dropping out