35/36W EL34 cathode bias

[Tof]

I think maybe the actual design could make it works and add something special.

Here are the datas I found that defines the tube specs in push pull cathode bias situation.

Load Impedance Raa : 3400Ù
Common grid 2 Rg2 : 470Ù
Common cathode resistor Rk : 130Ù max 700kÙ
Supply voltage Vb : 375V
Anode to earth current Va+VRk : 355 350 Volts
Anode Current Ia : iddle 2*75mA, 2*95mA
Grid #2 current Ig2 : iddle 2*11mA, 2*22.5mA


So I'm not sure about the PSU of the 36W ... I think for this kind of operation a new OT with 3400 primary will be suggest and maybe an another PT and an another design of power supply.

What do you think about it >

Is it a good Idea ?

[Tof]

That could be an another kind of 36W

[zevoz]

Let me get this straight. Are you saying put two EL34's instead of two EL84's in the output section of the 18 watt circuit for approximately 35/36 watts?

[Tof]

Almost, maybe it required more voltage ... Never tried it ... and it required for sure an another OT ..

[zaphod_phil]

Let me get this straight. Are you saying put two EL34's instead of two EL84's in the output section of the 18 watt circuit for approximately 35/36 watts?

You would need to reduce the PI tail resistor to 15k, to get more drive to the EL34 grids, and use 470 ohm screen resistors. The numbers shown above looked a little conservative to me. I would suggest a B+ of around 400V to 420V to get 40+W out. And you also need the 3400 ohm (up to 4000 ohm) OT.

[Tof]

In other word, we need a plexi 50 or JTM45 OT to do that.... ?

[zaphod_phil]

Absolutely.