Bob Latino wrote:Most people think that David Hafler and Herb Keroes who started Acrosound transformers "invented" the ultralinear amplifier in the early 1950's. What actually happened was that a British inventor by the name of Alan Blumlein was granted a patent (in England) for the an ultralinear type transformer in 1937. Blumlein never used the word "ultralinear". Blumlein also never developed the design in England because he was killed in 1942 in a World War 2 related plane crash.
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
Bob, this is great stuff. I have always said Hafler and Ultralinear in the same sentence. This will enhance my erudition in tavern conversations with other tube nuts.
Other than that, WTF are you doing, working on the 4th of July? It's time to send the dog and cat to the basement and red-plate some tubes!