I have both headphones and speakers plugged into my motherboard’s analog output jacks. It’s a pretty standard Windows desktop setup, the motherboard does HD Audio which has 5 analog jacks which can be programmed to do different things like speakers, headphones, line-in.
Also pretty standard, my computer had the RealTek HD Audio Manager installed, an ASUS skinned one. This does a nice job of popping up a dialog when the user plugs in new speakers and asking them to configure it. Unfortunately it also seems to have a behavior where when I plug in headphones it automatically silences the speakers. In fact both analog outputs show up as a single “Speaker” device in Windows, there’s no way to use them independently.
In theory the Realtek driver has option settings to reconfigure this behavior, to let you use the rear and front jacks as separate devices. But my version didn’t have those settings, no “Playback Device” section at all.
Following some cargo cult advice I solved this problem by just uninstalling Realtek entirely. Goodbye 500 MB of stupid reverb effects I’ll never use. Turns out Windows 10 itself can manage the audio hardware with no problems. I did have to unplug and re-plug the devices for Windows to detect them, but now my speakers and headphones show up as separate sound devices.
While I’m here, a little theory on how this all works in Windows. Each sound device is an independent output channel for apps to play to. Most apps just play to the “Default App”, which you configure in the Sound control panel or with a program like SoundSwitch. But some apps let you choose a specific output device, particularly games, and you can use that to play different sounds simultaneously through different apps. There’s also a notion of a “Communications device” separate from the usual default, I think for VOIP apps like Skype to use a headset always.
I’m still confused about what drivers are involved. Device Manager tells me stuff is being managed by Microsoft’s Driver 10.0.14393.0, which I think is just Windows 10. But Sound tells me that there’s also a RealTek Controller which a RealTek Driver 126.96.36.19910. I wonder if Microsoft ships that, or if I didn’t uninstall that driver when I uninstalled the Realtek Audio Manager?
Update: this stopped working after I rebooted.