Micromark801 passive instrument problem

[JamieMJL]

Hello all, I’ve got a micromark801 combo which sounds fine when using an active bass but the volume drops dramatically to virtually nothing when using a passive bass. There isn’t a separate active or passive input and there’s no switch either. It didn’t used to do this and sounded fine with either type of instrument. Any thoughts on what’s happened?! 

[BassmanPaul]

Does the amp have a gain control? if yes turn it up.

[JohnH89]

There is no gain control . It should work fine with active or passive basses . Are you sure the problem is with the amp and not the bass ? Try the passive bass through another amp to rule out problems with the bass .