While trying to set the volume control on the HK unit, I noticed that the range goes from -9 to 0 to +9 after pushing the musical note button. What exactly do these numbers mean? I can't seem to tell any difference in setting the unit at any of the ranges. I am trying to achieve more volume. Any help appreciated.

 

You cannot change the volume of the unit overall. Perhaps you were in the AUX level adjustment control, which changes the input volume of anything plugged in to the AUX input.