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variable bias? what's that and how to make?


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6/16/2000 2:37 PM
dmot
variable bias? what's that and how to make?
someone recently advised me to replace the bias inside my vintage MARS tube amp (24 yrs old) with a variable bias...  
 
what's that?  
Is that easy to make? what are the pros and cons?
 
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6/16/2000 2:58 PM
Benjamin

DMOT,  
 
Basically you would be replacing a fixed resistor in the bias supply with a potentiometer to adjust the negative voltage to your power tube grids. This is just an easier way to service the amp when retubing.  
There is no performance increase........ just convenience :>)  
 
Look at the transition in some fender blackface amps from fixed resistor to potentiometer. that should get you steered in the right direction.  
 
 
Benjamin
 

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