Could a tube buffer be useful for a Non-Inverting Gainclone?

[Sherman]

Originally posted by Joe Rasmussen


...Yes, the isolation of a separate transformer is highly desirable for the reasons mentioned already, but the single largest reason is simpler than that.

The question seems to be repeating itself, can I avoid the second transformer? NO, you can't....

Joe R.

Joe,
Thanks for that synopsis! All is clear to me now (it can take a while for stuff to make its way through my thick skull sometimes).

I'm ordering a second transformer for my project. Now to decide on one big case or a smaller case with separate PS.

Things are quite hectic right now but I hope to be able to give this a shot in a month or so!

[Systeme_D]

thanks Joe.

Your design is elegant, and it is definitely a compliment. Yup many ways to skin a cat.

Yes it takes a while for the tube to stabilise and also the psu caps too.

I intend to use the TDA7294 which has the muting function, and tune the start up timing accordingly. The B+ regulation will be slow start too. Filament supply from separate small trans, and maybe leave it on always.

cheers

[Sheldon]

Joe,

You didn't state it directly, but I'm assuming that the reason you don't leave just the filament supply on is that there will still be some instabillity while the tube current comes up - that and it's simpler to have the two switches instead of three?

Another unrelated question: In your commercial circuit (as opposed to the simpler DIY one), I assume that the cathode resistor is spec'd for similar current as for the DIY? What would you suggest for the grid resistor? I'll completely understand if you want to keep that under your hat, but I'll gladly take the answer(offline too), if not. These discusssions are very helpful in learning practical applications of stuff I've started digging in ref. sourced for.

Sheldon

Sheldon