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previous: Steve A. Dave:  &n... -- 3/30/2000 3:36 PM View Thread

Re: Plate loads?

3/31/2000 2:25 PM
Dave H.
Re: Plate loads?
"I guess if I really want to build an AC30 clone I ought to bite the bullet and get a more suitable PT..."
Thatís youíre best bet. Think of it as a "sound" investment. With an AC30 PT you can get 30W from 4 EL84s, 4 6V6s, 2 6L6s or 2 EL34s so if you donít like the AC30 you can turn it into something else. Thatís what I did. With the same PT and OT Iíve used 4 EL84s then 4 6V6s then 2 6V6s cathode biased and 2 6L6 fixed biased so I could switch between 15w and 30w output.  
Iím not sure whatís inside the Tone Bones. "Class A" is probably just cathode biased so the grid would have to be AC coupled to remove the -ve bias and there would have to be a parallel resistor and cap in series with the cathode for bias. EL84s are more sensitive than 6L6s so youíd need to attenuate the signal to the grid. Youíd also need a zener (?) to reduce the plate/screen voltage by about 100V. Fixed bias is simpler- a couple of resistors to attenuate the grid signal and zeners to reduce the plate and screen voltages. The OT impedance is going to be low for EL84s unless you can change the speaker tap.  

Steve A. Dave: -- 3/31/2000 8:15 PM