I’ve been a user of Cubase for almost 10 years now and this is the first time I encounter this problem, so I am not sure if it is Cubase or possibly an issue with the audio driver on my current laptop, a Lenovo ThinkPad. I’ve had Cubase on both Mac and PC before, but regardless of the OS, I have always been able to seamlessly switch between earbuds and speakers for output. For example, I’ll be working through my earbuds and then decide I want to listen through my laptop speakers, so I simply unplug my earbuds and the audio would come out of my laptop speakers automatically.
On my newest laptop, this isn’t the case. I have to manually go to the Control Panel under the Audio System section of Studio Setup and switch to a different output port. This then switches my Audio Output to “Not Connected” so I then have to click on Audio Connections and select the appropriate output. Were I to not do this after unplugging my headphones, there would be no audio output. Conversely, if I plug in my headphones without doing this, the audio continues coming out of my laptop speakers.
The following worked for me on a Toshiba laptop running Win 10. Insert the head phones and make them work as you describe.
Open the sound control panel and select the headphones as the default audio device.
Since I had this problem myself I tried to remember what I did to make the switch automatic. It’s been a while, so my memory is blurred.
It might have been in the Realtek Audio Console (obviously only available if your laptop has a Realtek sound device).
Just in case you do here are my settings. German only but you’ll manage. On the left hand side select “Advanced Device Settings” to get this view.