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]

Originally Posted by soundbrigade

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]

Originally Posted by soundbrigade

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]

Originally Posted by feralmeida

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]

Originally Posted by feralmeida

- 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%202-3.pdf
And here are curves: Gu50 Set ?