Help with a Tube amp (Power Transformer and Output Transformer)

[eduardo_gj1]

Hello, in advance I thank people who can help or provide any comments that can help me.

I have a diagram of a tube amplifier that I would like to do, the question is that I have no information on the power and output transformers, I would like to know if you can help me with this dilemma.

I wrote to the people of Madamp that they are the creators of this amplifier but they only tell me that the specifications of the power transformer are in the documentation, which is not there, but gave me some specifications for the output transformer.

Output Transformer:

Class AB, Pout: 3 W, I DC: 2x 16 mA
Raa = 8 k: Rout = 8 Ohms and 16 Ohms

Can someone send a link where I can find this transformer?

the power amplifier, it would be very helpful if someone gives me information or a link from where I can buy it too.

ahh I almost forgot, they told me that both transformers are custom made.

 

[eduardo_gj1]

sorry not power amplifier, its power transformer

 

[Visitor]

The power transformer details are on the schematic. 230v primary with a 200v secondary delivering 70mA and a 6.3v secondary delivering 2 amps.

 

[Nigel Goodwin]

Pretty well anything valve these days is going to custom, why not just buy the kit?.

50 years ago such transformers were commonplace, and you would have had a large selection to choose from - but that's not been so for a very long time.

Here's an example output transformer, but I've no idea what the specs might be on obscure Russian valves:

N35A002F | Chassis Mount Audio Transformer 3 → 15Ω 3.5W | RS

uk.rs-online.com

As shown above, the mains transformer specs are clearly given.

 

[Reloadron]

The power transformers like that once roamed the earth like dinosaurs but unfortunately have gone the way of the dinosaurs. As a kid I used them in my projects. They were commonly called a "Plate Transformer" and generally had a single or multiple high voltage outputs along with a 5.0 Volt and or 6.0 volts outputs which was for the tube (valve) heaters like shown in your drawing. Hammond makes a

250V C.T. @ 115ma.

6.3V C.T. @ 2A

The 200V secondary in your schematic is a little low for a plate transformer. Here is a data sheet for Hammond Transformers. Since this is a 250 volt secondary you can likely get by increasing the value of R22 in your schematic and maybe increase it to 5 Watts verse 2 Watts. I did not look at the data sheets for the tubes so haven't a clue as to their max working plate voltages or how much power the final. My old Sylvania manual reflects a max plate voltage of 300 volts and thet being the 6N6G.

ahh I almost forgot, they told me that both transformers are custom made.

That's nice, so they assume you will just wind one?

Ron

 

[eduardo_gj1]

Thank you all for your quick help, well, I don't buy the complete kit, because I already have all the components of old projects, and they don't sell only the OT and PT.

question: the link for the about its the right output transformer? or its a example?

Pretty well anything valve these days is going to custom, why not just buy the kit?.

50 years ago such transformers were commonplace, and you would have had a large selection to choose from - but that's not been so for a very long time.

Here's an example output transformer, but I've no idea what the specs might be on obscure Russian valves:

N35A002F | Chassis Mount Audio Transformer 3 → 15Ω 3.5W | RS

uk.rs-online.com

As shown above, the mains transformer specs are clearly given.

 

[Reloadron]

The link I gave you is for a Hammond Manufacture power transformer. The secondary is 250 volts verse 200 but it is still made. Since I haven't a clue as to your location I can't suggest a Hammond vendor. If I were you I would start with a Google of "Plate Transformers" or similar.

Ron

 

[eduardo_gj1]

ok thanks, i live in Dortmund Germany, so, i think i have to write to some dealer so meaby they can give me a good price,

I would like to know your opinion about making this amplifier but instead of being wired, do it on PCB, since I have a CNC machine I could do the PCB without any problem. but I would like your opinion about it

 

[Reloadron]

Would I build it? Nope, mostly because of difficult to find the tubes (valves) and the hand wound transformers. However, it's entirely up to you.

Ron

 

[rjenkinsgb]

There is a whole range of toroidal valve amp transformers here; it's possible there are suitable ones - power below and output transformers in another menu on the left:

Toroidal Transformer Amplimo - toroidal-transformer.com

Toroidal Transformer ONLINE SHOP. Order quick and save via our webshop toroidal-transformer.com All our items are immediately available from stock.

www.toroidal-transformer.com

 

[Nigel Goodwin]

Thank you all for your quick help, well, I don't buy the complete kit, because I already have all the components of old projects, and they don't sell only the OT and PT.

question: the link for the about its the right output transformer? or its a example?

A bit of both, it's an output transformer of a similar power, and suitable for push pull circuits - but I've no idea how well it would match the Russian valves.

I don't know if this will help or not, but it's a page from a book I have "Radio Circuits and Data 1948 (reprinted 1950).