Shame on me! I am very sorry xispe is right. From volume-level 25 and up the hack works Thank you to himdman!!! (I have a nh900 and changed the A1 value to 25 (MANUAL --> 113 --> changed value)
well, I think it's the "placebo-effect" But I hope that someone will find a hack for boosting up my device 3mW pro channel is not enough for good HIFI-headphones