Sony NW-ZX2 Volume issue

[zanefox]

Hey, Guys. I am currently using Spotify on my Sony NW-ZX2. And a wired volume issue keeps buging me. The Spotify's volume is much lower then any other players. No matter what I done (toggle volume limit setting, adjust stock eq setting, adjust Spotify volume bar), nothing works. Spotify is always about 40-50% quitter than other players.
Do you guys have any idea to fix this?
Thanks in advance.