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GU50 Screen Driven, DC Coupled

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matejsirk

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Joined 2008
marsaudio.eu
#1
My new idea with GU50. Screen driven and DC coupled. Is that possible?

Very first schematic:
 

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#2
It is possible, but screen drive is not very linear and high driving level is required.
With 100 Vpp the output power is some 3,3 W (2k5 OPT), THD = 6 %
With 240 Vpp, 13 W, THD = 14 %. Distortion is mainly 2nd harmonic.
All the above values are from LT Spice simulation.
 
#4
By connecting the cathode-resistor of the second triode to the first triode's cathode you get a positive feedback.The portion of feedback has to be less then the amplification of the first triode or else the circuit will oscillate.
Mona
 
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