ngower
Well-Known Member
There have been a few redesigns, per some emails with him about this very question.The Sutherlands were designed at different times. The Insight is actually a better built, AC-powered version of the older, battery powered PH3D.
The 20/20 was more of a clean sheet design keeping with Sutherland's dual mono principles.
Since the Insight was originally produced, Ron has substituted the 10K loading with a 475 ohm loading, per reports from other N&G owners.