Simple SE GU-50

[Einric]

I agree that the 25W Edcore would be better for bass, but I'm trying to save money since it is my first tube amp project.

 

[revintage]

Hey Einrich,

There are no good options in the Matejsirk circuits. Forget about GU50 in pentodemode without NFB!

Will maybe put out 3-5W at 5% THD with Zout of a few hundred ohms.

If you want to build a Gubernator you should maybe opt for a driver with a little higher gain. A 10k OPT is not optimal for the lefthand triode at 500V. Something like 10k/600V/60mA should make it clip symmetrical at 10-15W.

Anatoliy, wasn´t there a thread a few weeks ago about this topic? Have you tested out the IRL max Ia in lefthand mode? Seems the LS50 datasheet has very low figures at max 30mA.

 

[matejsirk]

All of those options look great, they are also nice because my multimeter only goes up to 600V.
I will look through them an make a decision.

Would an Edcore GXSE10-6-10K suffice for these circuits?
This would help keep the iron cost down.

How well do the 3.5K OPT's work?

I suggest GXSE15-6-5K. On first prototype I used XSE15-8-1.7K. It is OK. But 3.5K or 5K is better. Better bass and less distortion. My is custom made.

6J52P is noval tube. It is similar D3A. You can get curves here (for D3A): http://www.hifitubes.nl/weblog/wp-content/philips-d3a.pdf
and for 6J52P:
http://www.rutubes.com/articles_for_description/datasheets.htm

here is a picture of my amp:

 

[matejsirk]

With 6J52P I measured 11.5V on terminals with 8Ohm load before cliping. This is 11.5*11.5/8/1.41 = 11.5W. But I do not know how to measure THD. I have old Hameg and one analog and one digital multimeters. Is there possible to measure THD with that equipment?

 

[Wavebourn]

I agree that the 25W Edcore would be better for bass, but I'm trying to save money since it is my first tube amp project.

In such case ECL82 tube is one of the best options, for starter.

 

[Einric]

With an ECL82 SE how much power could I expect?
Keeping it under 600V.
Is that a noval socket?

 

[Wavebourn]

With an ECL82 SE how much power could I expect?
Keeping it under 600V.
Is that a noval socket?

You can power it from couple of cheap signal transformers. Like, 120/240V an 120/6.3V

 

[costis_n]

Yep, it's noval, and cheap too. PCL82, even cheaper.

 

[revintage]

But I do not know how to measure THD.

Hey M,
The easiest would be to get one of the freeware analyzers available out there. About Zout, just load with a high-ohm load and the diminish it until you get half the output voltage and that load is equal to Zout. You can do this at quite low signal-level. If you have 11,5V peak at the terminal this corresponds to just above 8W into 8ohm. Nice looking amp by the way.


Einric,
About triode/pentodes E/PCL86 is also a nice tube with a more powerful pentode but weaker triode.

 

[djgibson51]

There is a data sheet with English words in it on Wikipedia. It's the one I referred to while following this thread