GU-50, GM70 and KT88

[feralmeida]

And the benefit of a Ri minor (write the autor)

Fixed bias (also in other tubes) allows to increase +B
to those 400V without problems.

Ra I suppose equal, 5K or 2K5 for 2 tubes, or more...
biasing 95mA per tube whit 2K8 3k? (better DF?)

Other diagram is biasing fixed, +B 400V and Ra 5K6.

THANKS

 

[Wavebourn]

Nope!
Much notice must be paid to the fact that g2 doesn't take more than approx. 250V.

It can swing up to 750V easy, when tied to anode (triode mode, 400V B+). When anode goes below (pentode mode) I don't recommend more than 300V regulated.

Also, try +12V on 3'rd grid. And self-bias (cathode resistor) is the best for class A. Fixed bias is needed for class AB.

 

[Svein_B]

Much notice must be paid to the fact that g2 doesn't take more than approx. 250V.

The limiting factor is the max screen dissipation. As Wevabourn says, it is not a concern in triode mode when Vg2 will not be above Va.

When connecting a+g2+g3 the g3 dissipation may be of more concern.
The Chinese equivalent FU50 shows a lower max power curve in this configuration (attached)

Svein

 

[feralmeida]

THANKS

Yes in SET or PSET g2+g3 to anode,

My first refer is PSE of HiFiNews.RU

 

[Wavebourn]

THANKS

Yes in SET or PSET g2+g3 to anode,

My first refer is PSE of HiFiNews.RU

It was designed by TV repair technician Sergey Sergeev: G3 is on a separate leg of the tube, so why don't try to strap it with anode, right?

As Svein_B says, in order to get more of clean power it is better to tie G3 to cathode.

 

[feralmeida]

- It says to connect to the anode for Ri minor of the tube.
- Other tubes that allow, EL34 for example I have seen connect equal (Bas Honerman)
- Fodder that 1º, the tube works more like triode. 2º avoid the limitation of Vmax. g3.

I do not know if it makes worse the sound, if we lose something of power supposing that we gained quality, as it says to Ri minor and major DF.

GU50 it is superior to the present KT88 (old years) or/and do not cost 1600$ quad, electrically equal to the EL156.

Jacmusic praises on GU50 tube of audio.

The schemes that encounter, for a single tube, confuse, same Ra 2K (JOGUIS), that 5k6 until the moment, or chinesse FU50 like KT88 or 6L6😕
But I will do, that it is a good tube, that this presenting/displaying much diversion DIY!! 🙂
Thank you very much by its participation and it helps

escuses by my Babelfish Inglish Translator
Fernan

 

[Wavebourn]

- It says to connect to the anode for Ri minor of the tube.

Ri itself does not matter; ratio Rload/Ri matters actually.

 

[feralmeida]

Dear Wavebourn
It is truth that is not many nor common connecting g2+g3 and anode.

You recommend the use to me of these tubes in SE/PSE,
by the sensitivity of my boxes, 90dB, fodder in the necessity of PSE 2 tubes.

400V is a good poin SET, and Ra?


to see diagrams is very confused, Ra 2K (really my first reference in Joguis for 1 tube) or 5k6 suddenly in a search google, now with the easy translation, so far I have only found the him, SERGEEV page, I do not know if is TV technician or guru audio.😕

THANKS and escuse the inconveniences, or if I have been able to him to offend

 

[Wavebourn]

Dear Feralmeida;

I would recommend you to search for Gu-50 triode curves, then draw your own load lines.

PS: Audio Guru and TV Technician is often the same. But more often Hi-end Audio Guru has no education in electronics field.

 

[soundbrigade]

I used to have a triode curve .... but where is that now??

Here are some data (and curves): http://www.pastisch.se/tubes/lampa/Glava 2-3.pdf
And here are curves: http://www.diyaudio.com/forums/tubes-valves/100509-gu50-set.html

 

[Wavebourn]

450V B+, 510 Ohm 10W cathode bias resistor shunted by 50 uF 100V capacitor; 2K 100 MA OT; 100 Ohm screen grid stopper connected to anode; G3 connected to cathode; 220K grid leak resistor to the ground (may be higher due to autobias).

That's it.

Can you draw it now?

 

[feralmeida]

Thank you very much to both!
some ideas already are being developed 🙂
I have OPTs 2K2 and 3K, alredy 100mA to try!

All the Best
Fernan

 

[soundbrigade]

I have had ideas of constructing something beefy (SE or PP) with GU50s, but the plans are sliding far down on my project list. At the moment GU50-PSE would be great using my Hammond 2K5 trannies, but I will use my EL156 instead.
Besides, there may not be space for a pair of GU50 in my chassis (monoblocks).

 

[Wavebourn]

EL156 has control grid closer to cathode than EL152 (GU-50), so it is easier to drive voltage-vise

PS: that Russian book on your site is quite lame...

 

[Wavebourn]

Here is some info you may enjoy:

http://wavebourn.com/pyramid-8/GU-50.jpg

 

[feralmeida]

EL156 has control grid closer to cathode than EL152 (GU-50)

Yes "soundbrigade",I confused EL156 and EL152

 

[soundbrigade]

PS: that Russian book on your site is quite lame...

But it's better than nothing. If you want to argue, wait til Fall when me and my wife come to USA ....

 

[Wavebourn]

But it's better than nothing. If you want to argue, wait til Fall when me and my wife come to USA ....

No arguments; just some random information from other sources, and author's silly comments. If to close eyes on comments it is kind of source of selected by the author peaces of information.

Don't forget to visit Pleasant Hill, California the next time!

 

[vicol]

all schemes for 300b are good for gu50, the same V(350-400V), the ~same bias (-50-60V), the same Rload (3-5k)
I built SE GU50 + ECC81 , Rl = 4Kom, nice sound .. Google translation

 

[soundbrigade]

Hope you and others understood the "wink". Much info on various topologies and various odd tubes can be found IF thsi inf is googled using Japanese or Cyrillic letters ...

And you should know, dear Wavebourne that we are dying to make a 4th trip to the States. But if the fr*gging Swedish boss at BP cannot plug the leaking tube in the Gulf, I guess we can walk across the tarmac .... 🙁