Industrial PT as PSE PT - is my solution correct ?

[kagliostro]

A friend want to build a PSE amp with multiple preamp and a pair of GU50 tubes in PSE configuration

The preamps he chose requires voltage from 300v to 400v

the GU50 in SE require 300v anode - 250v G2

he has this big industrial PT

Primary
0-230v-400v

Secondary
0-12v 50VA = 4.166A
0-18v-24v 2.8A
0-55v-75v 2.0A
0-95v 70VA = 736mA
0-115v 80VA = 695mA



and I assume the transformer will supply a bit higher voltage as the consumption isn't so high

I've think about to arrange the required voltage and I've draw this schematic



(Tra B1 e massa = Between B1 and GND)

the 20v winding is the voltage I can take between the 55v and the 75v connection on the 0-55v-75v windind

The reservoir caps are omitted on the draw

Do you think there is a better arrangement to be used ?

Thanks

K

[HotBluePlates]

I think you've got it figured out the best it can be with that particular transformer.

Good job!!

[PRR]

I don't like the connection between 20V and 55V. I'd have to re-draw that to be sure it isn't a dead-short when the rectifier is connected.

I think the GU50 will be happy at 400Vp 260Vs 100mA 4K load/tube.

Then we have this possible hook-up:

[kagliostro]

Thanks HotBluePlates & PRR

Also I was a bit confused about what PRR is saying

but I'm not 100% sure that the connection that way is sure wrong

I've draw the schematic in a way that is easier to be read

Can you confirm that in this way there is a short ?



Many Thanks Again

K

p.s.: I forgot to say that as data for the PSE of GU50 is used the EL152 datasheet



PRR the data you give about voltages and TU are for a PSE of 2 tubes or for a PP of two tubes ?

[PRR]

You have a half-wave dead-short:

[PRR]

A single-ended tube (or parallel tubes) can be run at "many" different voltages.

Re-adjust the current to stay below plate dissipation rating.

Re-adjust the load impedance for the new V/I ratio.

See attached suggestions for either 1,000V or 500V.

For GU-50:

Book:
300Vp, 250Vs, 130mA, 39W Pdiss, 2K load

New condition:
400Vp, 250Vs, 100mA, 40W Pdiss
Voltage is 1.33 times higher, current is 0.77 times lower, impedance changes 1.33/0.77= 1.73 times higher, 1.73* 2K is 3.5K.

[kagliostro]

Many Many Thanks PRR  

that image is better than a lot of words

Now I've read also your further post one thing isn't clear to me

300Vp, 250Vs, 130mA, 39W Pdiss, 2K load

I was thinking the data sheet say 18W for one tube - 39W refers to the consumption (input power) ?

EDIT: is late and my brain was confused - Sorry

meanwhile I had one other idea about to avoid the use of the 20v from the 0-55v-75v winding



what do you think about this ?

K

[eleventeen]

You can avoid any such short by just series-connecting secondary windings until you get the input voltage you suspect you will need on the input of a single bridge rectifier, using dropping resistors in a normal way to get the lower and lower voltages for the low power stages. One thing you *might* achieve by such an arrangement, particularly if you can switch OUT a 20-30 volt winding, run the amp at a lower B+ for a lower power setting.

Only one bridge.

[kagliostro]

One thing you *might* achieve by such an arrangement, particularly if you can switch OUT a 20-30 volt winding, run the amp at a lower B+ for a lower power setting

 

My friend want to use a pair of GU50 in PSE

he consider the 18W of one tube a too low power 

He has listened a 40W PSE and he want one 

K

[kagliostro]

My last choice is this (it is near at the proposal of PRR)



but I would like to know if you see contraindications in the use of a doubler like in my previous post

this schematic



Thanks

K

[kagliostro]

Yes the 12v winding will be used for the heaters

Here in Italy isn't so common as in Australia

but also us have some difficulties about the availability of low cost transformers

PT and OT are cheaper in the USA than in this side of the pond

K