I didn't lose sound but after the the Realtek A05 update installed the sound quality on my machine plummeted. Instantly sounded awful. Very grainy and overly bassy, as if the audio was coming from the bottom of a bass speaker Reverted back to the A04 driver but the sound quality has not returned to the level it was before the update. Perhaps some artifacts from the A05 update are causing issues.

Feels like the Realtek High Definition Audio Driver 6.0.1.8642 (A05) was quite an unstable release if it can cause two such drastic results?

I don't know if this will help y'all, but it fixed my problem with the sound. Download the new driver from the dell website. Go to device manager in windows and delete the device. Make sure to check the box to delete the driver also. Run the driver you downloaded. This is were I got the idea. https://www.techradar.com/how-to/how-to-reinstall-the-realtek-hd-audio-codec-driver

I am having the same issue. Sound got very bad after last update. 

Same issue on a XPS 9570. After a windows update the speakers disappear. Reinstall the drivers from the dell site and after the reboot the speakers show back up and work for all of about 7 seconds. Then the devices drop out and windows can not see any speakers on the computer. That's for the onboard speakers and the 3.5 jack. The dell monitor is still listed but no sound comes from it.

Same issue here (garbled sound, poor quality, etc. after A05 driver update).  Rollback of the driver did not fix the issue.  System restore to a point before the driver install restored the sound quality.

Thank you for your replies,

I found a solution (from here) to replace the "Intel Smart Sound" controller by a generic audio controller : 

1. Go to the device manager
2. Set view by connections
3. Find the Intel Smart Sound controller
4. Right click on it, then on "Update driver"
5. Choose a manual update
6. Choose from available drivers the "High Definition Audio" controller
7. Then the sound should be back !

I did this, but before some sound comes through my headphones there is a very loud plop sound.

edit: That solution comes from this reddit post

this is terrible, i have the same issue.  after the driver update, the internal speakers do not work.  i tried to roll back the update but speakers are still not recognized.  It would show and work for about a minute, then go back to not detecting it.

I've resorted to using bluetooth headphones, but the sound quality is off and the connection keeps dropping when it normally holds unless nothing is playing.  very frustrating

For me the latest audio drivers completely broke my system. Headphones now do not work anymore. I'm sick of these ticking bomb updates.