Distorted sound / control volume under iOS

[user-removed]

Hi,

I've got a problem regarding distortion on some tracks when I listen to them via headphones (Sony MDR-1000X in my case). For example, if I listen to https://open.spotify.com/track/5zOnoB8FdZudDcPX4O8WqF  there's a very noticable distortion at 1:19, when the singer sings the word "Piano" and the bass drum is playing at the same time.

These distortions happen on Spotify for Mac as well. But on the desktop, there's an easy cure for them: Lower Spotify's volume just a tiny bit inside of the app. To be very clear about this: Changing the Mac's volume doesn't change the level distortion. But slightly reducing the volume inside of Spotify does the trick. You can rise the Mac's system volume as much as you want, as long as Spotify's volume is slightly reduced, no distortion appears.

Now I would like to get rid of the distortion under iOS as well, but there doesn't seem to exist any similar volume control. Again, chaning the system's volume doesn't do the trick.

I've turned off the equalizer and audio normalization, set sound quality to "extreme" and are not away of any other settings which could cause distortion otherwise.

Any ideas?

Thanks,

Norbert