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RE: Small IDHT tube cathode bypassing

Posted by cpotl on July 7, 2015 at 05:45:08:
"A comment by a commercial amp builder recently that I read recently went along the lines that the cathode bypass capacitor for small IDH tubes (e.g. input tubes) essentially inaudible - that differences between capacitor types are inaudible."

One can get some estimate of how audible the effect might be by putting an oscilloscope probe on the cathode while a signal is playing. This will show how much audio signal is appearing across the bypass capacitor. For an ideal cathode bypass (with infinite ideal capacitance) there would be zero signal. There will in actuality be some non-zero signal, but with a competent design it should be so minimal that the difference between one type of capacitor and another should be inaudible.

Of course, what people think they hear is a very different story, more likely related to the price they have paid for the capacitor...

Chris