When David Hafler and Ed Laurent started Dynaco Corporation in 1955 they used the ultralinear circuit design that Hafler and Keroes had refined and patented in 1952. All the Dynaco tube amps used the same basic (ultralinear) output stage. All the VTA amps also use the same ultralinear output stage design. A lot of information on the advantages of the ultralinear output stage design and the work of Blumlein, Hafler and Keroes may be found at the two links below. It makes for good reading for those that are interested in ultralinear tube amp design.
Ultralinear amp design link 1
Ultralinear amp design link 2
Last edited by Bob Latino on Fri Jul 04, 2014 5:43 pm; edited 1 time in total