OS X: Increase granularity of audio volume controls
Solution 1:
Hold Shift + Option while you change the volume with the keyboard. You get 4 times finer volume control.
Solution 2:
option-shift volume up and option shift volume down
will change the volume in smaller increments.
Solution 3:
What worked best to adjust the volume is going to Audio MIDI Setup and adjusting output volume by going to the device and editing front-left, front-right.