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previous: Tarrie Bruce, thanks so much for the reply... -- 1/5/2000 5:29 AM View Thread

Re: Guytron amp - bias and tube pulling questions

1/5/2000 7:06 AM
BillRe: Guytron amp - bias and tube pulling questions
quote:
"I guess the only problem I would have in pulling tubes is knowing where to set the new bias. How MUCH less current would be the question."
 
 
You should check out Randall Aiken's site, he has some good articles on biasing.  
 
http://www.aikenamps.com  
 
The general method is to look up the max plate dissipation for the tube in question. An EL34 is 25 Watts. Mulitply the max dissipation by 0.7 or 0.6 or 0.5 or .....  
 
For example, 25 Watts * 0.65 = 16.25  
This is what you are going to set the bias current to give you. Measure the plate voltage with only 2 tubes in (wait a minute for things to warm up). Then use the equation P=V*I .  
 
P = 16.25W  
V = value you meausred  
and I = P/V  
 
Enjoy.