Just received this from the original owner. During the 70's, he had a tech install a master volume in the presence potentiometer location. Tech was professional enough to return the original parts. Owner was cool enough to hang onto it for this long ha! The last time he fired the amp up was 40 years ago. The amp has its original tubes and drivers. The Jensens were reconed by a woman who lived around the corner from the owner; she did the work from her house! Will have some internal/progress pics as we move along. This thing is so clean! What a privilege; I do feel so grateful to have this piece of history on my bench.