GU50 Screen Driven, DC Coupled

[matejsirk]

My new idea with GU50. Screen driven and DC coupled. Is that possible?

Very first schematic:

 

[artosalo]

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.

 

[TonyTecson]

it's been done here....EL36: Applications in Audio

 

[Ketje]

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