A Dufrane audio transformer is a high frequency custom transformer, and is designed to isolate an input circuit from an output circuit and provide filtering to a signal that passes through it. It is designed to operate on signals with a frequency spectrum in the audible band.
Unlike power transformers which operate at low frequencies such as 50 or 60Hz, audio transformers are designed to operate over the audio frequency range, that is from about 20Hz to 20kHz or much higher for radio-frequency transformers.
Dufranes custom audio transformers require adherence to strict quality and output standards in the design and winding process, which is a reason for increased testing to insure a proper output which is noise-free.
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