Is it possible
to attach ( with a proper connector ) an "isolated"
midi device directly to the soundblaster midi joystick iinterface?
I don't think so; one is a voltage-level interface, the other is more
like current-loop. (ICBW, of course.)
However, if "with a proper connector" is taken sufficiently
liberally, the answer is "yes"; there exist interfaces that are built
into DA15 shells - you plug the DA15M it into your joystick port, and
it breaks things out into three connectors: a DA15F for the joystick
(if any) and two MIDI connectors for, well, MIDI. Mine cost me CAD
34.45, TTC, around the middle of last August.