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The "Shire Three" Interstage Transformers

Interstage transformers were very often used between LF stages in early battery sets. Commonly they were of 3:1 or 5:1 step up ratio. This voltage magnification was an important source of gain. It depends on the ratio of the source to driven impedances being significantly greater than the inverse square of the voltage gain. The high impedance of the grid circuit of a valve is essential. This coupling method is the primary reason for the low anode impedances designed into most battery triodes used as detectors and LF stages before the output.

Interstage Transformer
Interstage Transformer
Interstage Transformer
Andy Cowley, 2005    Home