how to gain voltage in a rectifier tube based PSU

[eledanca]

Hi gentlemen, A friend of mine, ask to add some power in a single anded tube Amplifier, I tell him that it is possible to gain the power doubling the voltage of the PSU.
To rise about 8, 10 Watt I need About 400V that's quite standard.
the main problem is that he want to use the rectifier tube, this condition make this task mutch more complicate. so I make first schematic that works

but it rise the voltage of about 3 times the starting one: 700V.
Ok I will put a Zener back biased in the central tap of the tranformer to produce and control the drop to get my 400V, it works, but we totaly loose the softstart action of the rectifier tube, so I elaborate something that i never seen before.. ( nether the preview acqualy )
and I'm not able to understend if this can works, maby the capacitors before the anodes can hurt the tube for a reason that I really do not know, or the concept is wrong at the begin , I need the help of someone skilled then me.

maby there is a simpler way.. I do not kow
comments please
thank you

MiK.

 

[Eli Duttman]

Increased power O/P requires an increase in the VA rating of the power transformer.

There is no free lunch!

BTW, are you going to change the O/P transformer? Can what's currently installed handle more power?

 

[JMFahey]

With due respect, do the things the right way.

You want to keep the tube rectifier?
Ok, your choice, then I would simply get a new power transformer with suitably higher voltage secondaries, and of course higher VA rating.

Do not apply a kludge which brings new problems, which wil be "solved" by another kludge which will bring newer problems, which wil be .....

 

[eledanca]

thank you gentelmen.

well changing the power tranformer is the easy way ( what a surprise ! )
here the task, is to know something new.

the original thansforme has 260V @ 400mA so it can be use easly.

Mik.

 

[Koonw]

Another way is to replace GZ34 with 5AR4 or 5U4G will give you more output power, but not sure that is power level increased you look for:
SS, 5U4, 5V4, 5AR4, 5V3 & 5Y3 Rectifiers Compared In 75 Watt Vacuum Tube Audio Amplifier - YouTube

 

[eledanca]

the power amp is dual mono so the power tranformer are 2
with the new bias poin I need 400V @ 110mA ( or litte less ) for 1 ch.

Mik.

 

[Ketje]

I think this is the best way to get more out of the supply and keep the warm-up delay of the tube.
Originaly the voltage was arond 300V, like this you get 350V.
Mona

 

[kuroguy]

A cap in front of the choke will also raise the output voltage

 

[Ketje]

A cap in front of the choke will also raise the output voltage

No.
Mona

 

[kuroguy]

No it won't or no you don't like that option?

 

[Ketje]

No it won't or no you don't like that option?

First option 😀
Mona

 

[eledanca]

I think this is the best way to get more out of the supply and keep the warm-up delay of the tube.
Originaly the voltage was arond 300V, like this you get 350V.
Mona

This Is a very interesting option, anyway I do not know if I Will obtain 350 VDC , that tube Loose about 20v per anode.. I'll consider It.
M.

 

[eledanca]

A cap in front of the choke will also raise the output voltage

Yes, in my schema It happenn

M.

 

[trobbins]

There is a cap in front of the choke in post #7 - see C1.

 

[Ketje]

This Is a very interesting option, anyway I do not know if I Will obtain 350 VDC , that tube Loose about 20v per anode.. I'll consider It.
M.

But the two anodes are paralelled so max 10V drop.
And an capacitor after the tube doesn't help since there is allready one in front.
Mona

 

[eledanca]

I see
M.

 

[kuroguy]

There is a cap in front of the choke in post #7 - see C1.

Sorry. I missed it on my little screen.