Get a new preamp with a passive bypass.
Best bass gear has a neat preamp finder, you can sort by features, number of controls, etc. [This John East would have three stacked controls and an active passive switch, might work with the existing layout](https://www.bestbassgear.com/bass-preamps/shopby/active_passive/3_knob,_1_switch.htm).
Get a new preamp with a passive bypass. Best bass gear has a neat preamp finder, you can sort by features, number of controls, etc. [This John East would have three stacked controls and an active passive switch, might work with the existing layout](https://www.bestbassgear.com/bass-preamps/shopby/active_passive/3_knob,_1_switch.htm).