Admiral 372-5R, 1940
All American Five tube complement: 12SA7GT mixer/oscillator, 12K7GT IF, 12SQ7GT detector, 50L6GT audio output, 35Z5GT rectifier.
Approximately 10-1/4 inches / 26 cm wide.
|About the All American Five circuit|
The story of radio in the early decades is one of continuous and rapid technological improvement. Early radio designers struggled first with problems of reliably detecting radio signals, then with problems of reliably amplifying them. Eventually, with advances in vacuum-tube technology, and the invention of the Superheterodyne circuit, it became relatively easy to design and produce radio receivers with excellent performance and stability. In fact, radio technology improved so much, so quickly, that by the late 1930s it was possible to achieve very good performance with just five tubes and a few external components. Most such five-tube circuit designs quickly settled into a common pattern. The tube functions are listed in the table below. Over the years the pattern stayed the same, but the tubes changed as new types were developed.
Manufacturers often deviated from this chart. For example, my Lyric 546T uses the 1941-42 octal-base AA5 tube complement except for the audio output tube, which is loktal. I presume that most deviations occurred either because of a shortage of a particular type, or because it was necessary to exhaust the stock of an older tube or an associated component.