iPhone 4s iOS 9.3 here; How to adjust the sound balance of the audio in very small db increment? My right ear hears slightly less compared to my left, (around 1.6-1.8 difference than the left if Windows' Audio balance is to be used as reference). 

I manage to change the audio balance just fine on my PC, Android, and WP, but on the iPhone I can't due to it's automatically setting the slider to 0 when it's near the centre... which is around where I'm at... Is there a way for me to adjust it to my circumstance?
The slider control is much improved on iOS 10 - I find that once I start to drag left or right, moving my finger below the slider substantially lets me see it move in very small increments and let go precisely where I wish.

I do use newer hardware, so you might be out of luck with iPhone 4s and iOS 9 if you can't get such a small fine adjustment with either a stylus or your fingers.