It was noticeable as soon as I turned it on. I did a quick ab before I left with the combo. I have two portible amps and really do not use them so I figured what do I have to loose to try it. I was surprised at the improvement and it made feel better to not have to buy a new dap to get it. Tomorrow I will try the other amp I have it's the one from alo the mkii3b I think it hissis low until the music starts and then goes away. But it a really detailed Mp as well. The iBasso have all those extra chips to play with too. So I figure it's time to play.
Now keep in mind the jh16 are the hardest to drive and the most annoying when it is not right as well. Overall enjoy that dap . It's two years old and I think it's still top shelf.