Where electrical engineers, sound engineers, objectivists, and audiophiles all disagree is the concept of Negative Feedback. You can't measure an amp on its own and determine much at all.
Do people know that a design like the O2 creates several magnitudes more distortion than a Single Ended Triode amp ? How can that be and it measure so well? Well the O2 design cancels its internal distortion with very heavy Negative Feedback. I built an O2 and yes it does a great job of cancelling its high distortion with NFB without resorting to such a high bandwidth that it is susceptible to oscillation, it is a unique design, very very black background and perfect if you think the job is done at the headphone jack.
But I don't think things end there. Thorsten Loesch posted an excellent article that shows huge amounts of 2H distortion added (or subtracted) by the ear, no one knows how it works.
But it isn't too far fetched to imagine that a more accurate amplifier is one which is linear in amplification without NFB, possible our perception is part of the feedback loop ? Chew on that.
If thats the case then the old roaring 20's direct heated triode designs just might be more "neutral" and maybe Lynn Olsen knows a bit more about acoustics than a recent EE grad with a dScope.
But then again I could be wrong, all I care is my high efficient phones sound better out of my SET amp than my O2. But the O2 is a fine fine stable stable low noise design and kicks the snot out of the SET with inefficient phones just don't think its the end all be all of neutrality.
There is a mid-buck DIY SS alternative to the O2 brewing that is similiat to the old Sansui/Pioneer integrated topology for power hungry phones, can't wait to put it together. These disagreements and non obsolutes are what make this hobby interesting and fun.