4 x EL34 Mark II JJ Matched Quad NEW TESTED (4 x JJ EL34 Mark II)
Having said all of that, the EL34 II is certainly fatter in the middle range and tighter in the bottom end in the standard JJ EL34. As a result, it will have a longer life than the standard EL34. EL34 versus EL34 Mark II: which is best?.