Overcome Low Volume Output on Tinker Board (3.5mm jack)

I have to connect a Tinker Board with a amplifier, but while the amplifier works perfect when is connected with a smartphone, laptop, etc.. , using the same cable when connected to Tinkerboard the volume output is low. Same problem when i connect headphones. I checked the sound settings, they were at 100db and i had the volume on Max. I need help to overcome it by using additional hardware or other suggested solution (for example hdmi audio extractor, or preamp module , etc)