I've just built an home-made cable to charge my smartphone and the smsl x4 with an external battery pack. Both the x4 and my android smartphone are gonna recharging BUT my device doesn't recognize the x4. This is the scheme, I'll appreciate any suggestion: EDIT: Just found a way...

This means I'll try to build one by myself :D I've done it yet for my pc external soundcard to power it, maybe changing something it could be possible..

Does anyone know if there is an otg cable to connect both the dac (micro-usb) and, at the same time, recharge the smartphone (usb type c)?

Yes, I do :D It sounds really good, definetely better than any portable devices I have at home and my macbook pro 13 too. No problems with Android (UAPP, Poweramp). Not really good for high impedance headphones but perfect for in-ear. I use it also with MacOS, Ubuntu and Windows w/o any issues.

No problem here with SMSL X4. I'm really satisfied of it.