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14th January 2013, 05:10 PM
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#1 |
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diyAudio Member
Join Date: Feb 2010
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Pentode curves for GU 50 SE amp with 700V B+
hi I have breadboarded a GU 50 SE amp in pentode mode.B+ is 700V G2 is 250 Volt and my transformers Ra is 2,5k.I know that Ra is a bit low for that but the transformer is a left over from some other project. At the moment I use a 470 ohm resistor with 220uF for cathode bias,but I want to calculate the right resistor.Unfortunately i can only find triode curves but i need them for pentode mode.
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14th January 2013, 08:58 PM
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#2 | |
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diyAudio Member
Join Date: Jan 2011
Location: Shanghai
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Quote:
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14th January 2013, 09:46 PM
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#3 |
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diyAudio Member
Join Date: Jan 2012
Location: Ulm
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Ub=700V is used for PP class AB, you will not get satisfying result for SE operating mode.
If you want to use pentode mode: Just as a top down estimation you should go to B+ of about 400V, GU50 operated at about 80-100mA . Then you could use your OT with 2K5. Looking to the datasheet you need a bias of about 25V. I would start with Rk of 270 Ohm. Have a look here Help with these Russian GU50 tube amplifier (GU 50 SE in Triode mode, this might be a better solution) Last edited by es345; 14th January 2013 at 10:05 PM. |
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14th January 2013, 10:00 PM
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#4 | |
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diyAudio Member
Join Date: Jan 2011
Location: Shanghai
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Quote:
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15th January 2013, 12:55 AM
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#5 |
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diyAudio Member
Join Date: Sep 2006
Location: Pleasant Hill, CA
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Here you go:
__________________
If I disappear suddenly, that means I finally created a time machine and pushed wrong button that brought me to Stalin's Russia. In any experiment any result is the result. Even if it is negative. |
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15th January 2013, 05:42 AM
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#6 | |
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diyAudio Member
Join Date: Feb 2010
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Some more
Quote:
 Ik is about 55mA at the moment.Ig2 is about 2,5 mA.I just wanted to try it,because i have a bunch of GU 50.I have to say that I use it as a guitar amp,so a certain amount of non linearity is very welcome.As driver tube I use a 6J9P at the moment. I also tried triode mode but pentode sound is better (and more powerful of cours).Anyway many thanx for your thoughts and of course the data sheet link. |
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15th January 2013, 05:43 AM
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#7 | |
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diyAudio Member
Join Date: Feb 2010
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Sorry
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15th January 2013, 06:23 AM
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#8 |
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diyAudio Member
Join Date: Feb 2010
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funny thing,now it works
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15th January 2013, 08:20 AM
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#10 | |
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diyAudio Member
Join Date: Feb 2010
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I meant
Quote:
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