Okay, I have what is probably a very nOOb question. Just got my Wiim Mini and got it hooked up via the optical cable from the WiiM to my DAC (Topping E50). The DAC is connected to an integrated amplifier via RCA. So ... how do I set the source on the amplifier? It has four Inputs, two of which are being used. It also has Phono, Portable, and FM Tuner sources. The WiiM works if I connect it directly to the amp via the Aux Out to the Portable jack on the amplifier, but I want to see how it sounds if I run it through the DAC. But I don't understand how to set the source on the integrated amp. Am I missing a step somewhere?