Optimal volume range on CJ preamp?

I own a CJ CT5 preamp and was wondering if anyone knows the optimal range of the volume control. The settings range from "0" to "99" and I generally stay between 40-50 with one amp, but 65-75 with another. Am I introducing distortion by operating it with the volume that high?

No, on the contrary, some say pre amps sound their best when "opened up" (i.e. higher in the volume range). And I have to admit that has been my experience, for whatever its worth.