I'm looking for the best way to connect any portable device I have (like my phone) up to the coaxial input on my AMP/DAC combo Aune X1S. Due to hardware restrictions I can't use the RCA inputs on the back as you can't use the RCA outputs to output sound to another amp while using the RCA inputs...

I'm currently trying to hook up my phones, a Samsung Galaxy S6 and Moto X 2nd gen, to my my Schiit Modi 2 through the use of an OTG cable so I can make phone calls and hear whoever I'm talking to through my headphones. I've gotten it to work through the DAC and AMP but when I plug anything into...