Thanks for replying. Then samsung did something different to the note 9 android 9. I am testing wired headphones + reset fully the app + tried firstly your advice. The audio even with dvc on is affected by dolby atmost on/off, literally the effect is applied + the volume is low and bad quality. If I can help you any further - will do gladly, otherwise you can get your hands on note 9 on pie to check it out or wait for further feedback as the rollout is just starting + note 9 exynos Poweramp users are not that much in the numbers, so it will take some time for the reporting.
P.S. I am tech heavy person, and also on top of that rooting + customizing android phones for like 10+ years, I am sure I am not doing some lame things leading to my OS problems with Poweramp's hifi output. That note 9 is full stock tho, so it's not my doing for sure.