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RE: Cathode bypass cap removed and I like it

Posted by Tre' on January 11, 2017 at 10:15:19:
"Fixed bias" is a funny term.

Fixed bias is when you have a negative supply, that is usually adjustable, feeding the bottom of the grid resistor placing a negative voltage at the grid and the cathode is connected directly to ground (in your case the CT of the filament transformer would be connected directly to ground)

Self (or "auto bias", or cathode bias) is what you are doing (with or without a bypass cap).

The DC plate current flowing through the cathode resistor places a positive DC voltage on the cathode while the grid is at zero voltage DC.

The tube is now biased because the grid is negative WRT the cathode.

In the end the tube doesn't really care how the bias is accomplished as long as the grid is negative WRT the cathode by the correct amount.

Tre'