How to connect HeroBox Pro to a stereo amplifier

Hi, I’m trying my Herobox which I received a few days ago and I would want to connect it to my stereo power amplifier.
I tried to connect the only audio out that I see (headphones one) but I hear only a humming noise sound. So I try to put headphones in it and they actually work. So, how to connect a speaker to the chuwi? Is there a setting to change?
Thanks.

Are you using a TRRS jack plug for the audio out. I tried initially with a TRS plug which did not work. Ordered a TRRS plug and now it is fine.

Note the extra R the correct jack plug is the 4 contact version.