Tinysine TSA (8804) gain structure

Hello,

i am embarked on my first DSP/Amp trial and ran into some issues regarding the gain structure with this board. While programming and measuring it with REW i got the board very easily into clipping (REW output measured at 1.5 Volts Output) without getting even full power on the outputs of the board (was not trying to anyway). So my question in general is, does someone have/had experience with tinysine boards and is able to tell, how to approach this whole topping of using an analog input without getting it into clipping/distortion whilst getting maximum output possible?
There are some dip switches on the board which i did not even touch and i am running it with a propper 36 Volts power supply.
Would be glad to getting pointed into some directions how to avoid clipping with the analog inputs!

Greets Swany