According to Stereophile's measurements the input impedance of the JC-1 is 48K unbalanced and 91K balanced. That is high enough to be compatible with the great majority of active preamps, and even many passive (unpowered) preamps. Also, the JC-1's measured gain of about 28 db for both the unbalanced and balanced inputs is likely to be suitable under the great majority of circumstances.
Good luck. Regards,
-- Al
Good luck. Regards,
-- Al