Tube Power Amp

Hi

I'm moving to my new house, and I'd like to build a stereo  tube power amp for a pair of speakers I've liying around (65W each).

I want P2P, as I'm thinking in one of those fancy amps with the tubes and transformers on top of the case.

Any ideas or schematics to start diggin´? I'm absolutely reluctant to audiophoolnes, I just want a nice looking and better sounding power amp for my ipod and turntable.

Thanks

I would suggest something based on a pair of EL34 tubes in ultra linear push pull would be a good starting point. There are loads of circuits of this type on the web. Check out the classic Mullard amp circuits:

http://www.louderandmore.com/mkgbs/Mullard-Circuits-for-Audio-Amplifiers.pdf

It is worth investing in very good quality output transformers as these are probably the most critical part of any tube power amp design.

Cheers

Ian

As Ian says there are a ton of schematics and stuff on the net.

You could check this site:    http://diyaudioprojects.com/Tubes/KT77-Push-Pull-Tube-Amp/

I have friend who is aiming to do the same but he can't decide what to do due to all the different possibilities

Best of luck

/John

you could use the line out's of a stereo receiver into a Williamson pwr amp,
that way you get a low noise pre and don't have to build tone controls,

sure would be nice to have a set of Mullard metal base 34's and a pair of Partridge OPT's but you would have to rob a bank,

made a pair of Peerless 16431's and am waiting to use them in a 100 watt per channel system,


http://oestex.com/tubes/williamson.htm

pro's and con's here>

http://groupdiy.com/index.php?topic=51361.msg652722#msg652722

hard to find a UL transformer for audio, plenty of guitar OPT's, might be flat enuff,

don't ask me to wind another 16431, sheesh,

Not totally DIY, but the classic Dynakit Stereo 70 is available again: http://www.dynakitparts.com/ST-70-KIT

Work backwards: See what output transformers you can find/afford, and base your circuit on that...

Jakob E.

7591 tubes are nice, there is a pair of Fisher OPT's on evilbay, great transformers,

I'm in the middle of the move,and I remember I have a RCA/Victor turntable with FM radio in a furniture from my grandpa inheritance.

At least the radio was working, I think it could make a nice sound system for my home.

Anyway thanks for the advice's, there are interesting things to study, specially that mullard book.

I'll post guts of it soon.

So, what speaker?

My next to do is some Audio Nirvana 12" in some home made baltic pine boxes 

To go with some really hifi SE amps and a pair of 7581a for each channel.

I'm just trying to find some traffos to do the  job - I want to use a opt with a feedback winding. Something different

Quite a custom ask, really.

How hard is something like that to wind, I wonder  (CJ ?) SIze is *no* object!

I'm thinking stereo pair on one chassis, psu on the other. But with *two* inductors, this time!

I love the SE 'sound', I also appreciate nfb (especially on  SE) - wherefore thence to go?

It has built-in speakers, I can't tell the model or the size.

The furniture is in a warehouse right now, I went this weekend to take a look and for my surprise is a solid state device. (Solid state stated in the control panel as something , maybe it's a early SS design), gonna look for more info now.

Good news are it has a Tape input, so surely I can put something there to play my ipod/whatever, thinking in a Raspberry pi running an wireless audio receiver.

It's something like this but more elegant in the front, just a plain wood with wooden grids on each side covering the speakers

That's so nice - woodwork and speaker, the pinnacle of real audio

CJ said:

sure would be nice to have a set of Mullard metal base 34's and a pair of Partridge OPT's but you would have to rob a bank,

Click to expand...

Years ago I bought a mono Denco 912+ Power amp, which is an EL84 design based on a GEC design.  It has Partridge mains & out transformer & choke.  I think I paid around £25 UK.  The 912 part stands for 9 octaves (grequency response), 12 Watts output.

When I was a kid we had a mono hifi my Dad made in a piece of furniture.  This eventually got given to my uncle whoc kept it for many years.  After my dad died & he realised I was into vlave amps etc he gave it back to me.  It was built into a bit of furniture with a tuner.    Anyhow when I got it back here I opened it up to see what was in it. Low and behold it had a Denco 912+ with Partridge mains & output transformer & choke. 

I've always planned to rebuild them and try them out in a stereo system.  Maybe one day ..........

How good do you want it to sound. I like a tube hybrid rectifier for slow startup and cleaner voltage and that less aggressive solid state edge. I like to drive the output tubes with a CF, I like balanced winding across the OPT kinda why I roll my own.  Layout is something to play with as well.

dirtyhanfri said:

Any ideas or schematics to start diggin´?

Click to expand...

How much power do you need ?  Will ~10W do ?

Those old green Philips  HF309 (mono power-amp, (2) EL84, ECC83, EZ81) and the related HF306 (stereo preamp) DIY-kits fetch pretty insane prices, so there could  be some merit in these parts & the design  (much written about that). 

https://www.youtube.com/watch?v=m0ga8ojJor4


For a make-your-own, the iron might be hard to come by,
but the schematics  & documentation (mostly in Dutch though) might be of use.

For stereo i like EL84 and ECL86 in the power amp.
You can look for heathkit schematics - these amps are sweet
There are also availble manuals with drawings how to wire p2p step by step.

Being an electronic engineer all my life i have built a lot of tube amplifiers.

In the 60's when i was 14 years old i built my first amplifier. The concept was based on an article i found in Radio Bulletin-Elektronics. The article was called "The last of the Mohicans".
The amplifier had an EF86 as a pre-amplifier, an ECF82 as a phase-shifter and 2 EL84 as a pentode in the output. The schematic was a close clone to the wellknown Radford STA15 amplifier. Later the concept was changed to have a STA25 amplifier with 2 EL34 tubes to raise the output.
I used this amplifier until the mid 80's and then rebuild the amplifier with 2 KT88 for a 100 watt of output. I've never heard a better sounding amplifier. This was because of the use of that ECF82 as a phase shifter which is not often found as a phase-shifter. I will lookup the schematics from my collection and make them available to you.

Close to the village where i lived then (and live now) there was a city where a guy lived by the name of Menno van der Veen. Menno is a real tube amplifier guru and he founded his own company called "The Tube Society" Menno gives many lectures and presentations at several AES conventions all over the world. Also he has written many books on the subject of tube amplifiers. I can safely say that my Tube-Bible is the book Modern High-End Valve Amplifiers  based on toroidal output transformers
(ISBN 0-905705-63-7) written by Menno.

On his website you find a description of a project he wrote and that is very helpfull in understanding the concepts of tube amplifiers.

It's a universal amplifier concept where you can build some 20 different amplifiers and sort out what is convienient to you.

The designs range from 5-80 Watts output with selectable primary and secondary impedances, which include Single Ended and Push-Pull with Triode and Pentode configurations .

All the components are very easy to obtain. This includes the Power and Output Transformers.

For the tubes you have a collection to chose from :

EL34/KT66/KT88/6550/EL156/6CA7/6L6

Only the input driver is Always the same : ECC81/12AT7

You'll find the schematics, explanation and construction here :

http://www.mennovanderveen.nl/eng/index.html 
In the menu on the left hand you choose "The Project"

Radford-STA15 Schematics

Radford STA25 Schematics

Radford STA25-Renaissance Schematics with 5550A in the output