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RE: Small IDHT tube cathode bypassing

Posted by SETguy on July 6, 2015 at 14:34:15:
Here's another option for you to consider which should work quite well with the 6C6: Try grounding the cathode and use a 10 meg grid-leak to create the bias (this necessitates AC coupling to the source)! I use this method almost exclusively when using high-mu triodes in the front end (and contrary to popular belief, this does not result in hum issues); some pentodes, like the 6C6, also can be used that way. GE published some recommended values for the plate/screen load as a function of supply voltage which you can look up (if you can't find it, look up the 6J7- same tube electrically). The advantage of this method is that there are no frequency response issues, elimination of 2 components from the signal path and, as the tube ages, it will automatically adjust its bias based on the available space charge.