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previous: Nutshell Ehm.. I forgot one thing..<... -- 1099765199 View Thread

Re: Bias conversion SF to BF

11/6/2004 8:17 PM
Re: Bias conversion SF to BF
yes, the 15K sets the negative bias voltage that goes to the grids of the power tubes.  
changing this ohm value will change the negative voltage, which then biases the tubes to a different idle current.  
making this resistor variable allows for convenient adjustment. you would not want to reduce the ohms very close to zero because of tube damage, so the resistor of approximately 6800ohms is put in series with a new 25K trimpot. Therefore the stock factory amp has a fixed 15K setting resistor; after modification then the range is adjustable from 6800 to 31800ohms.  

Nutshell One more thing.. -- 11/9/2004 1:05 AM