Need Some Help, Please

I’m completely ignorant with regard to wiring things. I would like to get into the world of tube amps for my headphones, so I bought an inexpensive one (the Apos Gremlin) to get my feet we. It will be here Sunday. I will be using my iPhone and I have a FiiO BTR17 DAC/amp, which cannot be set as a line out only. My question is can I just set the BTR17 to phone mode and connect it to my phone, and then use a 4.4 mm cable to go from the BTR17 to the dual three pin XLR inputs on the back of the Gremlin? I do have a male 4.4 male to three pin xlr on the way. I would genuinely appreciate any help.