^ yea, I can definitely hear the dx90 amp turn on through my iems, like a very soft pop followed by the low hissing of the amp, that is completely normal. You also should be able to hear two clicks from the player when turned on, the clicks are not heard through your iems, but from the dap itself, so leave your iems out of your ears, and listen for the clicks from the dx90 on turn on. The clicks are normal, they are the relays stopping really loud pops from going through your earphones. If you are not hearing the clicks from the dx90, then the relays are not working and there will be a very loud pop through your earphones. Make sure your dx90 is actually broken, not just operating normally like I've outlined.
I don't hear any pop or clicks even through an iem. The clicks from the relay is there but it's coming from DX90 not through the HO.