Hey @Leendert Hakvoort!

If you check your audio settings you can download in Flac version as well. 

Thanks for the response @Yula 

 I know that I can download Flac files. But my phone doesn’t have the storage to download a 1000 songs in Flac. 

Hi @Leendert Hakvoort I understand that your phone doesn’t have enough memory for 1000 songs in FLAC, however, we don’t have an option to download in Low quality and then be able to listen to the same download in HiFi as you asked. You’ll need to download in FLAC in order to listen in FLAC later.

 

Of course it is understandable that a downloaded song can only be played at the quality it was downloaded with. But the point is: if you’re online Deezer should not play the downloaded version of a song but the online version. For instance I have all my Favourites downloaded with HQ quality, so of course I accept that if I play them when offline they play at HQ. But if I play my Favourites while online they also play only in HQ. This is not OK: I have a premium account and pay for HiFi, so I want to listen in HiFi while online. After all Spotify can do it that way: if you're online you get the better quality if a song was downloaded at lower quality.

I agree and think on wifi connection or mobile unlimited plan you like to stream best quality. 
But if you are in a situation depending on downloads HQ quality is the best compromise between quality and memory usage. 
Imho this could be done if downloaded files only are used from the menu „favorites“…„downloads“ or even better only after switching within the app to „offline mode“ in settings section. 
I‘m going to post this at ideas… 

Please vote for it.

I would also love to have this functionality, listen in HiFi on wireless and to the downloaded song on mobile data. I have been waiting for this function for a long time now.

The suggestion to download HiFi quality on a limited storage mobile device is crazy, there should be an option to stream instead when WiFi data is detected and available.

@charlbur@gmail.com 

As you can see above you can vote for the idea.