How can I play digital music via the DAC in my DENON DM39 ?

Hello audiophiles,

Just recently, I bought myself a Hifi micro set. I bought the Denondm39 with a pair of Dali Zensor 1s. Now first of all, i love it. 

The CD' s sound wonderful, especially in the mid and high range. But i dont want to spend hundreds of bucks on CDs. I want to play FLACs and mp3s via my cell phone, via the DAC in the unit.

Therefore, I need to connect my smartphone to the receiver. 3.5mm jack to usb. 

But such a cable only exists for apple devices. There is also the option that I put a usb device in the receiver, in wich I can put a 3.5mm jack cable. But I don' t know if these usb devices  only work in an pc, for example. 

and maybe there are other options to play my digital music via the dac in the unit?

Is there anyone who can help me with this, it will be highly appreciated ,

thanks

p.s. i'm Dutch, my apologies for the grammar 

Bart