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previous: Dean Hazelwanter I converted a single-ended console ... -- 6/21/2000 5:50 PM View Thread

Re: EL84 Bias Questions

6/21/2000 7:22 PM
Re: EL84 Bias Questions
Hi Dean:  
I can't actually answer your questions, but I can give some data.  
In the GE book the example conditions for cathode bias 6BQ5 in single-end Class A service (the only operating point listed) have 250V on the screen & plate, cathode resistor of 135ohms, 48ma plate dissipation + 5.5ma screen diss.  
My 1967 Skylark has 250V B+ but a 150ohm Rk and does excellent, I tried 130ohms and found little difference in sound so I switched back. The original tube in this amp is still fine so these are probably good conditions for NOS tubes.  
If you continued with the setup you had, maybe you would find out most accurately whether there was reduced tube lifetime or a fire extinguisher was necessary. ;)  
Since you have already removed the other OPT, I guess you didn't consider bridging the output of your preamp to both channels' inputs and using separate speakers to double the power and maybe the tone? This seems like a good idea with identical channels and signals to each one but different speakers for adding lushness.  

Dean Hazelwanter Thanks for the reply Mike. I think ... -- 6/21/2000 10:43 PM