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    Building, troubleshooting and testing of these amplifiers should only be
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    the safety precautions around high voltages.

GU50 SE Amplifier class A , with 6SN7 Full construction details

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Hi,
So, today I desing and built :

GU50 SE Amplifier class A , with 6SN7



Full construction details and my experience with GU50 SE Amplifier can be posted here, or sent to email if you need that.






Best regards
Mario2005
 

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Thanks for your comment,
Actually i dont use that 250V Zener ,only for protect 2 grid from
high voltage in case 275V or more.

Andreas , can you suggested capacitor value ,I can test.


I test russian triode 6N8S and have good result


If somebody need Transformers I have some excellent SE transformers in this range for 45 Euros . pair 90 euros about 115$

2K5/8R 140mA 25W

weight 4.5 kg or 9.9 lbs

Freqency response: 10Hz-45KHz (-3db)
EI-core 108 Waasner M 111-35 N

Toroidal power transformer 300W sec 320V.07A : 6.3V5A :6.3V5A :40V 0.6A for 35 EURO or 44$



Regards
mario
 
dung0981 said:
Hi Mario.
Can you give me more imformation about the power transformer that used in GU50 in parallel.
Can i have some picture of OPT you want to sell?
Thanks



power transformer is

Toroidal power transformer is 300Watts
Primary 220V ,
Secondary 320V.07A : 6.3V5A :6.3V5A :40V 0.6A
for 35 EURO or 44$

you can use if you have transformer 300-320V 0.5 A but you must have 2 * 6.3V and 4 A for filament


For GU50 you need 12.6V 0.8A - filament

40V is for bias or for PL519 (40V 0.3A) filament

GU50 in parallel need about 200 mA per chanal

I post photos of OPT soon.


regards
mario
 
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Joined 2006
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Nicely LOOKING amp but ...I just hope... (considering the big bucks asked for that amp) that the design is up to the looks....
After looking at Marios amplifier "design" I am not sure it is...
simple Kids stuff selling for £££? Oh my...what is te world coming too....
 
Member
Joined 2006
Paid Member
Nicely LOOKING amp but ...I just hope... (considering the big bucks asked for that amp) that the design is up to the looks....
After looking at Marios amplifier "design" I am not sure it is...
simple Kids stuff selling for £££? Oh my...what is te world coming too....
 
Official Court Jester
Joined 2003
Paid Member
gorgon53 said:
Nicely LOOKING amp but ...I just hope... (considering the big bucks asked for that amp) that the design is up to the looks....
After looking at Marios amplifier "design" I am not sure it is...
simple Kids stuff selling for £££? Oh my...what is te world coming too....

do you mixed Mario's design with prices from Bulgarian site?
 
Member
Joined 2006
Paid Member
Hi Zen Mod

Well Mario did represent a drawing of his own amplifier and also
mentioned that he work together with a Yugoslavian Manufacturer
of amplifiers before he represented a picture (and asked for opinions) about a very expensive amplifier made in Belgrad.
So I gave my opinion on that amplifier. Titanium isnt exactly what is needed to make a good amplifier, in the contrary, money is wasted onto something that contributes (at the most) only to good looks. Forgiv me, I am a old man and designed amplifiers for measuringeqippement in the range from 500Hz to 500kHz back in the 60th and I know from expirience that even a good amplifier
is kidstuff compared to designing a good broadband transformer
and a person really able to design a good transformer will have no problem designing a good amplifier.
But back to your question "did you mix up...", I propable did, forgiv me, I apologize. Marios transformer prices are reasonable if they are good, or lets say at least as good as Lundahls (remember Lundahl is located in Sweden wich has very high costs of workmanship, high taxes, high livingcosts)
And may I say, even Lundahl produces transformers that are badly compromised by using core sizes that where primilary designed to achieve low mass production costs, optimized for mainstransformers. Long magnetic pathlength (with comparable
small and squareshaped areas) would be a good start for a good wideband/low loss design. Is there any? Not that I know off, even expensive ones look like mainstranformers to me.
Multilayerwindings, interleaved, sure, but what about proximity effects, skindepth in said winding outlay (wich isnt the same than the skindepth in a wire surrounded only by his own field) not to mention ignorance toward dielectrical properties of the isolationmaterial....But gladly, we got pure silver, or at least OFC..
and high prizes...must be good? at least good enough to help
designers to spoil the advantages of a single ended transformer by either putting a airgap rigth into the middle of a coil or, even better, invent choke/capacitorcoupling just to reintroduce us to that lovely hysteresisinduced distortions of pushpulldesigns we wanted to get rid off in the first place...
No, in my humble opinion, neither tube amplifiers, nor transformers, even comparable cheap one,are worth the money asked for them...
The WWII LS50 is nostalgic to me, played with it s a kid, and the russian clone, the GU50 (at 1.50) is ok, but you get what its worth for 1.50, not less, not more...
So I repeat...Oh my, what is the world coming too...
 
gorgon53 said:

The WWII LS50 is nostalgic to me, played with it s a kid, and the russian clone, the GU50 (at 1.50) is ok, but you get what its worth for 1.50, not less, not more...

No.

$1.50 for very expensive in manufacturing tube does not mean that they are worse than mass production KT??, it means that they were used for powerful mobile military transmitters, but were too expensive for audio amps manufacturers, that's why they are not in demand, that's why they are so cheap.
 

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