I have got this problem of no output sound using Logitech headphones on Ubuntu 14.04. Previously, the devices shown in the Sound dialog, when the headphones were plugged in, referenced Logitech analog headphones for both input and output.
But now this setting, very recently, has changed to
Internal Microphone - Built-in Audio;
Digital Input (S/PDIF) - Lync Audio Device; Headset Microphone - Lync Audio Device ** this works on Audacity; Analog Input - Lync Audio Device
Speakers - Built-in Audio; Digital Output (S/PDIF) - Lync Audio Device; Analog Output - Lync Audio Device
I can't remember anything I did to initiate this change so I have no idea how it happened.
I now have no audio output thru the headphones. I'm able to input thru the headphones using Audacity, tho with a lot of noise.
The built in speakers and microphone work OK.
This is very puzzling. Any help would be much appreciated
9/9/17 I've tried Stackoverflow and here a few months ago seeking a solution to this irritating problem. In the meantime I've been using earbuds but I would prefer to use the Logitech headphones. I'm surprised that nobody has picked up on this problem, it would seem unlikely that this is a completely isolated issue.