No Audio Through Audiojack

I can play a sound file through the web audio. But when i want to play a sound through the jack-port on my pi3b. It doesn’t work. Alsa mixer is 100% and the standard is the jack, I controlled it.
So who can help me out?

The Raspi3B-audio.jack is only for earphone. Have you checked?

Yes I checked it. But I use an old stereo installation as my earphone. This should work. But in my case it doesn’t.