• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Universal Power Transformer

For me the hardest (most expensive) part about amp building is obtaining the right transformers.

I have found a friendly winding company who will 'do me a deal' if I order in quantity.

So that got me thinking. What would the ideal multi purpose power transformer look like. ?

How is this for start ?

400v - 0 - 400v @ 150mA
-100v @ 10mA
3.15v - 0 - 3.15v @ 2A
3.15v - 0 - 3.15v @ 2A
0 - 5v @ 3A

The idea is to be able to make as many different types and styles of amp using the same transformer.

I should add I love octal tubes and tend to use these for everything.

Comments welcome.
 

azazello

Member
2008-08-23 7:28 pm
USA
If you will use some output tubes with +B about 180-200v, I think, that secondary coil must be 200+200 - 0 - 200+200v. /middle tap from every 400v/. I have box with PSU with different +B, GZ34 and 2 filtering CLCRC channels and 2 output transformers - 2.5, 5, 10 konm Ra. And I connect my tubes
EL11, EL12, 1625, GU50, 6CH8, 6LR8, 4P1L, 30P1S, 6S4S, EL84, 6E5P......ets, with preamplifiers, of course....
 
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You go me thinking...

After posting the original question and reading your reply, it seems that now what I really need is a separate PSU chassis which I could use to drive any amp I build.

I could create all my future projects with a plug at the back and simply hook up the power supply to which ever one I was listening to at the time.

So it seems what I need now is a supply which can provide

B+ 400v @ 200mA
B+ 200v @ 100mA
C- 100v @ 10mA
+6.3v @ 4A
+12.6v @ 2A

Using this I should be able to create a whole host of interesting a enjoyable amps and only build a single PSU ?

What do you think of this idea ? Do you think the above voltages are flexible enough ?
 

tinitus

diyAudio Moderator R.I.P.
2005-11-24 1:47 am
well, Im not experieced with this, but found that supply trafos without heater windings tend to be cheaper
And I have seen a few cheaper standard trafos with possible heater voltage

I pulled the plug and ordered a heater trafo with 3.15-3.0-0-3.0-3.15, 5A
ofcourse its yet another trafo to handle

but I guess it also depends on whether its for DC or AC heater
 

artosalo

Member
2010-02-16 9:00 am
I have once built this kind power supply. It is based on Italian Inmadout-transformer, which is very reasonably priced (some 50 to 60€). (see www.inmadout.com)

[IMGDEAD]http://kuva.termiitti.com/image/14796.gif[/IMGDEAD]

Here the bias supply was done from 12-0-12 filament output by doubling the voltage. This output can also be used with tubes requiring 12,6 Vac for filaments.

Also both 450 Vdc and 225 Vdc is available.
 

LinuksGuru

Member
2008-08-16 4:57 pm
I'm use this transformer for my bench power supply:

Primary - 230 V
Secondaries:
2 x 189V / 400 mA
1 x 30V / 400 mA
1 x 70V / 100 mA (for BIAS)
3 x 6.3V / 10A
2 x 3.15V / 10A


This is toroid transformer is absolutely silent and went only slightly warm under heavy load.

It is connected to stabilized vacuum-tube based regulator, capable of 1A 360 - 460V.
 
The transformers, power and output, required for a tube amp have keep me from building from scratch. My reasoning goes this way: I figure the most economical way to get transformers is to salvage them from an old amp. So I purchase an old beat up amp from some swap meet. Then I start looking at the chassis, and realize that the socket holes and sockets are already there, the layout is a proven design done by professional "tube" engineers, and there is no way I could possibly make a case that looks as good as what I already have in my hands. So I land up doing a restoration instead of a DIY. :sly:

Bobby Dipole
 

artosalo

Member
2010-02-16 9:00 am
I don't like the idea to share unfinished and problematic design and let someone will waste time and resources.

No hurry. Take your time. I am just designing a linear HF-amplifier for my ham radio station. It uses one GU81M tube and my intention is to build 500...600 V stabilized screen voltage regulator. Therefore I am interested to see all ideas.
 
No hurry. Take your time. I am just designing a linear HF-amplifier for my ham radio station. It uses one GU81M tube and my intention is to build 500...600 V stabilized screen voltage regulator. Therefore I am interested to see all ideas.

If you need low-amperage screen supply you can take schematic of stabilized regulated supply from L1-3 or L3-3 vacuum tube testers.

You can download both schematics from my blog:
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