Can I use the C Series Front End Interface without a PowerLab C?

Yes, you can connect directly to a PC but the host PC must have a USB-C Port able to supply enough power to power the Front End you have connected (7.5W minimum, 15W recommended). The device synchronization, mains filtering and other features enabled by the PowerLab C will also not be available. Note that only a single Front End Interface can be used in this configuration and that any Front End with more than 4 channels is also not supported.