No, it won't work because coax-out is, well, S/PDIF coax-out, and therefore it is a digital signal intended for another DAC.
On the other hand, if you plug the cable into the line-in / line-out jack (the one next to the headphone-out jack), it will works as just an DAC, as you wanted, to avoid double amping.
Thank you. And here I thought they were the same ports! So which means:
1. Source (Smartphone/DAP/PC dac) > line-in to E18 > headphone-out (E18 amp section will be used)
2. Source (Smartphone/DAP/PC) > usb/usb otg to E18 > line-out to external amp > headphone-out from external amp (E18 dac section only used)
3. Source (Smartphone/DAP/PC) > usb/usb otg to E18 > headphone-out (both E18's dac+amp will be used)
Is this correct?
Though I'm still a little confused by how can I utilise the S/PDIF coax-out port of the E18.