Assuming you are using the Red and White RCA Phono outputs. Check the amplifier input you are using is a line level input. One marked CD should be fine.
Open the Box settings menu. Picture and Sound. Change Digital Audio out to Stereo.
Now Try turning down the amplifier volume (so you dont deafen yourself). Now turn up the box volume using it’s own remote to max. Now turn up the amplifier volume to a suitable listening level.