Some possible possibilities: - The 4.4 jack is not inserted completely to make good connections? It does take more effort than the other jack, especially when new. Have heard this happen to folks before. - The Fiio BL44 is defective? - Some problem with your DX160's 4.4mm jack. Maybe some lint or dirt causing poor connection? Try inspecting/cleaning? - Or maybe the 4.4mm Jack's solder joints? If solder joints, sound may improve/cut out when you try to wiggle the Fiio BL44's 4.4 tip. - Some problem with your DX160's balanced circuit.