Some IEMs hiss to some extent no matter what device you plug them into. I tried some cheap impedance adapters which fixed the hiss, the IEMs also sounded better. I was very surprised at how high it needs to be raised to get to a decent loudness level, with an IEM that is usually very loud at 20% volume it may need to be raised to about 90%. The cheap adapters are very poorly made, both became loose after a few weeks use, the slightest tug of the cable dislodged them and their length makes them a hazard. I have since bought the 3.5mm IEM Match which is a very solid product and is easier to use on the go.