When you say original stage preamp, you mean the volume and bass boost knobs?
If so, they are only passive controls and its likely the piano will not work correctly with the suitcase speaker input. I actually think those suitcase cabinet jacks are line outputs and not input jacks at all. But maybe they can double as line inputs. Someone else may be able to confirm this.
The more ideal solution would be to switch out the passive controls on the stage for a modern suitcase compatible preamp that can then connect to the suitcase cabinet with the appropriate 5-pin cable. That would let you at least get closer to the original suitcase setup.
You'd want to be certain the cabinet amp and 5-pin outputs/input are working beforehand.
There is also the concern that the sustain pedal would work correctly. The stage piano case baseboard is thicker than the original suitcase piano base. You've also got the leg sockets to be dealing with so there may need to be mods done to make the cabinet pedal rod work with the stage piano.
If so, they are only passive controls and its likely the piano will not work correctly with the suitcase speaker input. I actually think those suitcase cabinet jacks are line outputs and not input jacks at all. But maybe they can double as line inputs. Someone else may be able to confirm this.
The more ideal solution would be to switch out the passive controls on the stage for a modern suitcase compatible preamp that can then connect to the suitcase cabinet with the appropriate 5-pin cable. That would let you at least get closer to the original suitcase setup.
You'd want to be certain the cabinet amp and 5-pin outputs/input are working beforehand.
There is also the concern that the sustain pedal would work correctly. The stage piano case baseboard is thicker than the original suitcase piano base. You've also got the leg sockets to be dealing with so there may need to be mods done to make the cabinet pedal rod work with the stage piano.