The Mk I has an all vacuum tube audio circuit. The Mk II has an all solid state audio circuit (not just the input stage....all) with only a single cathode follower at the output. The Mk I has all the best sonic qualities of tubes while the Mk II sounds more like a solid state unit, albeit a very good one. Take your pick based on your personal preferences. I vote for the MK I. To me, its sounds more like what I hear in life.
