Another tidbit is the frequency response change of 1/1,000,000 equates to
-114 to -120db down from the fundamental (one to one on the steepest part of the signal slope).
Even though small, the change covers octaves of bandwidth. Rane Corp found a change covering 1/3rd octave or less is generally not perceived.
A spec of +/- 0,1db equates a change of only about -54db. Not surprising to me that we notice sonic differences of different manufacturer's components even though the frequency response are the same, +/- 0,1db 20 to 20khz.