Jazzdog: PedalSnake - seems just special cables that combines more wires into one cable - so you can have power & audio in one, but you'll need to add another "power in" jack to your bass.
el_Kabong: EBS 9v phantom power - yes, that seems exactly like what I want - in the manual they say - if you want to use it, just remove battery from your bass and shorten + & - of battery socket, also have to use stereo TRS cables. However I didn't find any mention what electronics support this, and I'm almost sure that not every type.
But this seems to be the feature I'm looking for. I need to find some wiring schemes how to DIY (I've SWR amp and definitely don't want to switch for EBS because of this

) "phantom injector" (switchable 9 & 18V) & how to check/modify wiring of my active electronics.
I'm no electro guy, so if anyone could help with this / any ideas - more than welcome. I thing I should be able to find standard 48V phantom power wiring scheme, so possibly simplest way would be to modify it to 9V/18V.
thanks everyone for help, as soon as any progress I'll put it here (maybe more people would be interested in this.)
thanks, .stepan