I have looked everywhere for an owners manual. No luck. I have to say now that I have screwed around with it a good bit more that the button does do something. It does nothing to the sound as far as I can tell but it does do something. When I first started using it I had my DAC (the only input I am using right now) plugged into the "TUNER" input. When I pushed the "DIRECT" button nothing happened, no sound at all unless I turned the volume all the way up then very weak signal from both speakers. Now I plugged the DAC into "CD". After plugging it into "CD" pushing "DIRECT" button it sound exactly the same volume without using any other controls. Volume stays exactly the same and I hear no difference in the sound whatsoever. I can also cycle thru all of the inputs with the "DIRECT" button pushed in to its on position and the source music stays on. Same as before, same volume same input source plays no matter what is selected. This does have Balanced outputs ( HA.. I said "balanced" ) perhaps there is something I am missing there ? I am using unbalanced outputs.