I have a fender player plus pj bass. I wanted to upgrade the controls so I can use tone control in passive mode. Can this be done? Thanks!
Absolutely! You can even upgrade the tone knob to be either push/ pull passive/ active or stacked one for active and another for active.
There are lots of different preamps out there that will provide this functionality. The trick is in finding one that will fit in the available cavity and with the correct number of controls for your bass.
Many will use stacked and push/pull pots to provide the additional functionality.