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previous: Mike Trouble with (B) is this is a catho... -- 9/20/1999 1:33 PM View Thread

Re: Setting bias with tiode wiring

9/20/1999 5:28 PM
J Epstein
Re: Setting bias with tiode wiring
Caps block DC. It does not carry any of the DC current from cathode to ground. Your guess, can I apply Ohm's law, is correct and is probably easiest to do. Note that the 10ohm resistor trick is just an especially simple application of this method.  
The cap is there to bypass signal, which is AC, to ground, and so to prevent degneration - a form of negative feedback inherent in an unbypassed cathode bias circuit. By bypassing the audio from cathode to ground, the gain of the tube is increased, which is why it is used.