Well, upon futher listening I am indeed having the low/no sub output on stereo sources after the March firmware update. I'm also pretty sure that the volume levels are lower in the other channels. Sub appears to work correctly for surround sources.
Did the unplug reset. Didn't help. Did factory reset (and had to rerun Audyssey and reenter all my settings). Didn't help.
Called Denon, told them what I'd done. Asked if there was some way to roll back the firmware update. They said no. They said to try the sub 2 out. Did that, didn't help.
Called back to let them know sub 2 out didn't work either. Got a different person and asked them about rolling back the firmware. They said they would "escalate it to corporate" and someone would get back to me.
Got the following email...
...navigate a web browser on your PC to
https://usa.denon.com/us/downloads/productupdates and from there, input the serial number and model number of your unit into the field prompts. You will be redirected to a download page and a download will automatically initiate.
This download contains the previous firmware version files, which you can extract to a USB drive in FAT16 or FAT32 format and then install using the USB connection on the front panel of your unit.
Did that, and found the September 2016 firmware update which is the previous version I had.
Installed the Sept. 2016 firmware according to the included instructions and it resolved the issues. It also kept all my calibrations and settings, but I will probably rerun Audyssey again just because.
WARNING! PROCEED AT YOUR OWN RISK. I imagine that something like operator error, corrupt download, or a power outage during the firmware install could brick your receiver.
