The Hum X can only be used with a maximum of 6 amps output.
The 6 amp rating of the Hum X is how much current can be drawn through the HUM X ... not the amount of output of the CJ to the amp
The maximum amount of current that will safely pass through the HUM X is 6 amps ... you have to find out how much current your CJ uses to operate
What you need to ask CJ is how many amps does it take to run pre ... or how many amps does the preamp draw .... if its less than 6 amps the HUM X will work and pass enough current
Again the 6 amps HUM X is referring to is the maximum current it will safely pass not the output of the preamp to the amp