Originally Posted by Daniel644
root it then flash a custom kernel (most recent is Terrasilent 1.3.5) then install Voodoo Sound (you can't use voodoo unless you have a kernel that supports it, hence why you do the kernel first). Now (once you configure voodoo sound) you can max it out (atleast the headphones) this is how loud my headphones will get on my 4.0 with this configuration.
Also 30 is the normal MAX volume there are no numbers above it, just be sure you have a 4.0 and NOT a 4.2 (common mistake)
also there is a setting in the Poweramp EQ (far left Master slider) that can be maxxed to add a little more but you'll be more prone to distortion if you go that route.
My cowon player stopped at 30 but if you took the volume limiter off it, it would go up to 40.