GU-50 PP amp project - Any favs?

[DaveInVA]

A while back I bought a bunch of these tubes and sockets and put them aside awaiting time and motivation to use them. I am now at a point where I'd like to put them to use. I'd like to build a PP amp preferably using octal support tubes. I've done a bit of searching here and on Google and found a few interesting things but none yet that scream "build me". I've also looked at a few classic KT88 designs to possibly modify. I figured it would be best to post here before I get to far along and get some input from people with experience with these.
Does anyone have any sage advice or any favorite PP amp designs for these?

Thanks,
Dave

 

[AuroraB]

Maybe if you use Google or Babel to translate this....unless you read german?
I do, and this looks like a well worked project, but that's all I know about it, except the designer seems to have a name in Germany....

Gegentakt-Verstärker in AB-Betrieb fuer GU 50

 

[Wavebourn]

First of all, you need to think about output and power transformers, before thinking about octal tubes. GU-50 amp needs 8K P-P tranny capable of 100 Watt on rated bandwidth. It is not so easy to get good transformers with such parameters.

Also, you will need 12V 4A for filaments, 250-300V for screen grids and 700-900V for plates.

Are you scared already? 😱

 

[DaveInVA]

Not scared at all. I've been building and repairing tube stuff since I was 14 (mid 1960's). I grew up with this stuff. My Dad was general manager of Grommes and started there as an engineer their originally. Now I'm a retired engineer 🙂

Thanks,
Dave

 

[Wavebourn]

I did not mean high voltages; I meant very unusual transformers.

GU-50 sound like a charm in my amps. I don't have a complete schematic drawn, they have almost directly coupled drivers with servo, parallel feedback by voltage across output tubes, and regulated voltages for screen grids and drivers.

www.wavebourn.com • View topic - Pyramid-VII: home stereo vacuum tube amp

 

[tympani1d]

Try this one:
Google Translate
Seite 1 Startseite

Wavebourn: What do you think about this one. Maybe you could help us figure out how to make these transformers (for US) or better yet separate them (power xfmrs) into several smaller (modular type psu).?? I KNOW you've the skill and talent for it!!! Or use it as a launching platform for a different design here... maybe even group buy project? OHHHHHHHHHHHHHH, GU-50 OTLs.... now that's to drool for!!

 

[Wavebourn]

I ordered my transformers from EDCOR Electronics Corporation

I can draw full schematic of my Pyramid-VII, but I'm short of time currently. I even wanted to write an article for Elektor magazine about it, probably I will do that later.

 

[tympani1d]

Maybe if you use Google or Babel to translate this....unless you read german?
I do, and this looks like a well worked project, but that's all I know about it, except the designer seems to have a name in Germany....

Gegentakt-Verstärker in AB-Betrieb fuer GU 50

Google Translate

 

[TonyTecson]

got my sight at parallel PP GU-50, Anatoly, what would a quad of these per channel do in terms of wattage? B+ is going to be in the neighborhood of 700 volts...

 

[Jaap]

First of all, you need to think about output and power transformers, before thinking about octal tubes. GU-50 amp needs 8K P-P tranny capable of 100 Watt on rated bandwidth. It is not so easy to get good transformers with such parameters.

Also, you will need 12V 4A for filaments, 250-300V for screen grids and 700-900V for plates.

Are you scared already? 😱

What do you think of GU-50 designs with around 400 volt on the plates en 5K or 6K outputtransformers ?

 

[artosalo]

4 x GU50 as PP, 650 V +Ub, 250 V Ug2, Ra-a = 4k: Pout = 140...150 W, says LTSpice.

 

[davorin]

My amp with 8xGU50 per channel in progress!
Ua=640V, Ug2=300V, Auto-bias, P~2x200W

 

[artosalo]

That is huge ! But why only two other tubes with 16 x GU50 ?
Can you show the schematic ?

 

[davorin]

Tubes for input and drive are 2 dissimilar duo-triode13DR7 with inter-stage transformers (1+1:1+1; 10k:2,5k+2,5k; my own construction, calculated and winding in my hoby room).
I still have not the whole scheme drawn, but I will show you very soon.
Currently I'm looking for a suitable analogue VU-meter (large, but not too expensive!), and the entire project was temporarily stopped.

 

[artosalo]

I still have the whole scheme drawn, but I will show you very soon.

I look forward to see that.

 

[matejsirk]

Maybe one of my next project:

LTSpice simulations: Pmax 65W, THD less that 0.4%, Zout only 0.4 Ohm.

Matej

 

[pauldune]

What do you think of GU-50 designs with around 400 volt on the plates en 5K or 6K outputtransformers ?

I am curious too! Had something like this in planning...

 

[Zekk]

Sorry to've gate crashed the party!

I've a quad of Telefunken EL152 and will be delighted to follow this built.
Heard that it's similiar to GU50!?

 

[TonyTecson]

the GU-50 were copies of the EL152, the Russians captured the German engineers making this tube i heard.....

 

[artosalo]

GU-50 is copy of Telefunken LS50.

GU-50 - Wikipedia, the free encyclopedia

http://frank.pocnet.net/sheets/043/l/LS50.pdf


Simple and relatively low voltage (+Ub = 400V) version of GU-50 PP.
This uses budget OPT Indel TGL40/001.