Nord Electro 6: quiet output sound

[tomholo]

Hi Fellows,
I bought Nord Electro 6D few months ago and that was my 1st Nord purchase. Some time ago I noticed the output sound is half time quiter in comparison to my other instruments: Roland Fantom X8 and Hammond XK-2. Of course I can set equalizer properly and then the signal is much stronger (it's ok then) but the equalizer works for one sound only. So when I split the keyboard and use 2 different sounds (f.e. organ and piano), one of them will be equalized but the 2nd one will be still quiterer.
Anyone had the same problem? How did you solve it?