The Cathode Connection



Jack Elliano coined the term “Ultrapath” to name his cathode-coupled transformer design that he introduced to the audio community in Vacuum Tube Valley issue 10. In that design the signal is shunted from the top of the transformer through a capacitor directly to the cathode of the driver rather than having to pass through the power supply, as is the usual case. Lynn Olson took up the baton in his excellent article “Ultrapath, Parallel feed and Western Electric” in Vacuum Tube Valley issue 16. In this article he describes eight circuits for single-ended and push-pull amplifiers and calls the cathode-coupled parallel feed version “Ultra Parafeed.” In another article, “Western Electric, A Rosetta Stone for Triodes,”  Lynn traces the origins of cathode-coupled transformers to the very early days at Western Electric. In this article Lynn suggests that perhaps the term “Western Electric coupling” would be appropriate for the cathode-coupled parallel feed configuration, giving credit to the engineers who first implemented it. Another good reference for both parallel feed and cathode-coupled circuits is Paul Joppa’s article, “Twelve Ways to Parafeed,” in VALVE, volume 6, number 5. This article covers the gamut and describes every possible way to configure a parallel feed circuit, including cathode-coupled.

 In this article I have simply used the term “cathode-coupled” for circuits where the transformer is returned to the cathode of the driver.


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