At what volume are you listening with amp9? I have discussed this with a few people already, you need to push amp9 volume setting higher than your usual in Android mode. By that, I don't mean to make it louder, just that you need to dial it up to get to the same listening level as you would with amp8 or amp1km2. For example with one particular pair of my lower impedance sensitive iems, in mid gain from 3.5mm SE w/amp1mk2 my listening volume level is 75. Then I switch to amp9, and in mid gain from 3.5mm SE amp9 it's 105, but when switch to Mango OS w/amp9 - it's 55. Just sharing my observation without any "sound science" behind it. Don't know what's going in Android mode w/amp9, but for those who are afraid to push the volume and keeping it at their usual lower setting, you gonna hear more of that "waterfall" hissing, so push the volume higher.