Volume sample is low KP3

[iorio]

I have the KP3 , when sampling drum , playing back the recorded sample volume is so low that almost no hear . The volume of sample I put the maximum (shift + bank + high pad) . Is something going wrong ?.
I'm just using headphones , nothing connected to the input or the output

[iorio]

It also occurs to me the same thing for the line input

[mesoboy]

.
I'm just using headphones , nothing connected to the input or the output

How have you connected up what you are sampling?