The Manual for the 68C says you cannot use active pickups without plugging it into a line input rather than the instrument input. That means, unless I am incorrect, you need a DI box of some kind?
Instrument Inputs. The 1⁄4-inch TS connectors on Channels 1 and 2 can be used with passive instruments (guitar, bass, etc.). See Input Source Button for more information.
Power User Tip: Active instruments are those that have an internal preamp or a line-level output. Active instruments should be plugged into a line input rather than into an instrument input. Plugging a line-level source into the instrument inputs not only risks damage to these inputs but also results in a very loud and often distorted audio signal