When I connect my headset to my laptop running on Ubuntu 18.04.1, sound can only be heard from the right side. I have tried testing the speaker in the sound settings, which shows the same result. The headset works correctly when connected to other devices. I also checked with another headphone, which also had the same issue.

I have tried suggestions from other answers, such as [this](https://askubuntu.com/a/831453/625292) and [this](https://askubuntu.com/a/599082/625292), but they did not work. The following is the output from `alsamixer`:

[![enter image description here](https://i.stack.imgur.com/1TnY0.png)](https://i.stack.imgur.com/1TnY0.png)

So it appears that the bars for both channels are set to full. I also checked in the sound settings that the sound balance is at the centre.

How can I find the source of the problem, and resolve it?

Thank you.