Double Bass Help with Markbass 800?

[Betto]

Hello everyone, i'm fairly new here and would appreciate it if anyone could help me with my predicament. I own a Markbass little tube 800 with a Markbass 800w 4x10. I'm currently using an old beatup upright bass with a fairly new K&k rockabilly plus pickup system. The pre-amp that the pickup came with has 2 volume adjusters for the 2 pickups; one for the tone and the other for the nice slap/clicky sound of an upright bass. Every once in a while my amp gives me a great massive tone, and sometimes it doesn't, and i always have trouble getting that nice, clear 'click' from the fingerboard pickup. No matter how i adjust the EQ on the pre-amp, my amp gives me too much bass on the clicky pre-amp, so i have to run one pickup through the bass amp and hook the 2nd pickup to a mini-guitar amp to do the job. I think there might be a problem with the tweeter on the cab because iv'e used Ampegs and even cheap GKs and they give me that nice clean click i get from the separate guitar amp. Is there any way i could adjust the tweeter to give me that tone? Might it be turned off or something?