Direct-coupled cathode/source follower driver in PP?

[Bandersnatch]

Re: Re: Re: Re: OT: UL possible here?

Hey Doug,
Highly dependent on tap position.. Cmiller obviously should be less at 25% taping (near pentode) than at 43% or 50%.. On cursory inspection your equation looks ok.. Haven't thought about it much as I no longer do pentode or UL amplifier designs.

Kevin,
With pentodes, it is g1 to g2 capacitance that matters. Hold g2 'still' and g1 sees very little capacitance. Clearly when g2 has signal it will have multiplied the C just as in the triode/miller effect. Higher tap %-age and there is more effective capacitance seen by g1.
cheers,
Douglas

 

[kenpeter]

Do you agree with the following text:

output uebertrager => UL and neutralisation is possible.
output transformer => UL and neutralisation impossible.

ok?

Darius

Neutralize plates to opposing UL screens.
Neutralize UL screens to opposing grids.
Would it work?

 

[kenpeter]

Assume beam power, where the supressor grid is virtual.

 

[smoking-amp]

Hi Ken,
Probably working OK, but I don't see any point in the neutralizing to the screen grids. The plate still has to drive the same capacitance either way, either the UL tap point does it or the Neut. cap. from plate does the driving. From the UL tap it even gets some trashformer ratio to help out.

Don

 

[alwineden]

Here is one version of such driver, from my Alligator amp (drives triode-strapped GU-50 in A2):

I'm in the process of ear-testing a driver with 1n60 fets in an almost identical Allens SLCF inspired circuit compared to a standard White follower with 6n6p's and an 1n60 on top. The Constant Voltage and Current mode operation seems the way to go for ultimate stability. Both circuits sound a lot better to me with the one fet addition.

TM