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I have a vague idea of how I might be able to safely direct couple an output stage, do you guys think it would work ok? By using a dual rail power supply and the primary of a output transformer as a choke, the dc voltage of the bias for the following stage could be kept almost constant. For the supply, it is a center tapped power transformer with bridge rectifier and the center tap is the middle rail. Thoughts? Here is a basic idea:
Thanks!
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What do you hope to accomplish with the 5W single ended transformer? There is no bias on the pentode, it would burn up. Just use a resistor in place of the 5W transfomer so that current from the triode pulls the grid of the pentode below the +300 line to establish bias. Just control the triode current and plate resistor to set the bias. The 300V line needs plenty of filtering.
I'd use a 6080/6AS7 in place of the pentode. They need lots of negative bias, the mu is really low.WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
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The point of a choke rather than a resistor is that the low dc resistance of the winding holds the plate voltage of the driver tube steady at dc so that the bias of the output tube stays the same.Last edited by Austin; 01-30-2013, 07:13 AM.Comment
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It may be an interesting idea, but I don't see the advantage of having to have two high voltage power supplies to avoid using a cap.Education is what you're left with after you have forgotten what you have learned.Comment
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