Before we get into specifics on output transformer less circuits (OTL), first let us consider what the output tube must do that is different…

I have found Julius Futterman to be greatly misunderstood by those who write about his circuit designs. I have researched Futterman…

Julius Futterman, in a 1954 publication in Audio Engineering Society Journal, presented a 10-watt OTL amp without a power transformer…

Most published noise specs are useless as they do not give a proper reference. When they do it is often to full output, which still requires…

There has been a great deal of conversation about autotransformers (autofomers) in this forum. Many think they are like the output transformers…

Development of the EM-7 push pull 10-watt amplifier has led me to some interesting thoughts on the topic of transformer winding resistance and its effect on damping…

Amplifier classes of operation have been with us from the beginning of "Amplifier Time." The first amplifier engineers of the 1920s developed the terms Class A, B, and C…