[perpleSlerp]

Ok, so it seems the FM receiver on my 640 only plays in mono through the headphones, is this the case? And if so, why? Streaming music and Youtube play in stereo.

[milkyway]

did you try different radio stations? many are broadcasting in mono

[voidcomp]

It supports stereo but after channel surfing I'm surprised how many FM stations broadcast in mono. There were a few that were stereo. Back in the days nearly every FM station broadcast in stereo. Wonder what happened?

[perpleSlerp]

Neither phone will play any local stations in stereo, they all broadcast in stereo.

[Diamond67]

Many FM receivers automatically switch from stereo to mono if the signal strength is low enough. I'm not sure if this is the case with Lumia 640 though.

[voidcomp]

Neither phone will play any local stations in stereo, they all broadcast in stereo.

My Lumia 640 plays FM stereo just fine.