Update: issue solved. The SGR200 is not an active bass, it has a PHAT2 booster circuit in line but pickups are passive. With the PHAT2 connected there is 4.5v at the output. By bypassing the PHAT2 I can get signal to the Kemper. Obviously the voltage at the output is not an issue for amps or pedals. I bypassed it completely by connecting the relative wires in and out together, so it is completely removed. Just turning the booster knob down did not work.
I also got my hands on another SGR200 and that too has 4.5v at the output. So with the previous poster's experience, it would suggest that this is common on this model of bass.
To be fair to the SGR200, at its price point it's a playable bass, with good sounding pickups and it works just as intended in amps and pedals. Just has a preamp that lets it down. Sounds great now. Thanks for everyone's input.