earphone sound really bad. UMI Iron PRO

lamalamaduck

I have an Iron PRO, brand new. (still in warranty)

The speakers are ok but when i use the earphones the sound is very distorted.
The earphones work great on other devices. They just don't work with my UMI iron pro (Lollipop 5.1).
The sound is weird with the voice of the song disappearing and only some instruments are heard.

Do you think it's a software or a hardware issue?

Thanks.