Any suggestion for a 12AT7 / ECC81 SRPP powerstage ? - diyAudio
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Old 11th July 2012, 01:04 PM   #1
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Default Any suggestion for a 12AT7 / ECC81 SRPP powerstage ?

Hello,

I need some advice from guys who actually use a 12AT7 / ECC81 "SRPP" stage ( or rather "CCS" stage if you bypass the lower rk with a capacitor ) to drive power tubes eg. 2A3, 300B or beampower pentodes strapped as triodes.

I have some trouble finding suitable formulas in order to calculate the catode resistors. (valvewizzard´s homepage seems to be broken or at least the guy has used all his traffic..)

Best regards,

George
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Old 11th July 2012, 02:01 PM   #2
DF96 is offline DF96  England
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There are no formulas, apart from Ohm's Law. Decide on the operating point, using load lines, then use Ohm's Law. Finally, use SRPP design equations to calculate gain, Zout and Zopt. Decide if these meet your requirement, then either iterate to a solution or decide that the ECC81 with your proposed voltage rails can't met the requirement.
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Old 11th July 2012, 02:06 PM   #3
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... or use a pot to test the wright point dinamycally.
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Old 11th July 2012, 02:10 PM   #4
DF96 is offline DF96  England
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Quote:
the wright point dinamycally.
the right point dynamically? Osvaldo, your usual good English seems to have temporarily deserted you - is it too early in the morning for you? 8-)

Last edited by DF96; 11th July 2012 at 02:11 PM. Reason: typo - oops
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Old 11th July 2012, 03:38 PM   #5
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Originally Posted by DF96 View Post
the right point dynamically? Osvaldo, your usual good English seems to have temporarily deserted you - is it too early in the morning for you? 8-)
Ja, ja ja, perhaps, may be... I wanted to mean, to use a pot of a suitable value, and wattage, and adjust the stage bias with an audio signal and oscilloscope, and adjust the pot to the object searched, say, maximum output swing, minimum distortion at the same time you rotate the pot. It is not so engineering way, but still work best way for me.

If you would know what is my job actually....
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Old 11th July 2012, 04:33 PM   #6
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And, for learning purposes, which was my error/mistake?
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Old 11th July 2012, 05:53 PM   #7
DF96 is offline DF96  England
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Just creative spelling of 'right' and 'dynamical'! 'Wright' is an old name, rarely used today, for someone who makes something.

Are you an English teacher? That would explain your desire to learn from your mistakes.
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Old 11th July 2012, 06:12 PM   #8
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Just creative spelling of 'right' and 'dynamical'! 'Wright' is an old name, rarely used today, for someone who makes something.

Are you an English teacher? That would explain your desire to learn from your mistakes.
Ah, OK. No, a neglect typo.

Teacher, I? Nah!!!. I read and understand English (in fact only tech English), but I don´t speak nor ear. If very slowly speaking, I can understand some words. I´m of the rare specimen that can learn from my mistakes.
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Old 11th July 2012, 07:00 PM   #9
DF96 is offline DF96  England
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OK. Your English is very good, for someone who does not actually speak it.
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Old 12th July 2012, 12:27 PM   #10
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OK. Your English is very good, for someone who does not actually speak it.
OK, thanks for your comments about me. My mother always told me that I try to join with people better than I and not worse, so I´m here. And an old English teacher also told that the best way to understand a language is reading. And only can speak English when I can think in English. Several years later I agree with her.

But, sometimes happens to me that the brain goes faster that my hands in the keyboard, so I do some typos.
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