Crush 35B

[paul123]

Hi, everybody!
Well, i have a problem with my bass amp crush 35b.
The problem is that the tone controls aren’t working properly. There is a very small difference in sound in high and low positions of every tone control. And the low end response is very weak. I tried with different basses, it’s all the same. But when I use the headphones it’s ok.
Does anybody know how to fix it?