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Old 4th October 2013, 06:44 PM   #11
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Would you have the triode-connected curve for the 6AC7? I can try to build a model with them.
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Old 4th October 2013, 07:15 PM   #12
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Default 6LU8 with Ayumi's pctube

Here is Ayumi's 6LU8 model vs. the datasheet. Ayumi's model building process is described here. The key is not to use the Koren parameters...

Click the image to open in full size.

Last edited by jazbo8; 4th October 2013 at 07:18 PM.
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Old 5th October 2013, 02:09 PM   #13
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Here is the Ayumi 6AC7 model vs. the datasheet, while the knees do not match up well, the transfer characteristic is spot on, so it should still be good for voltage amplifier applications.

Click the image to open in full size.
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Old 5th October 2013, 02:17 PM   #14
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Mind translating that into English? The useful portion of the pentode curve is >50V
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Old 5th October 2013, 03:12 PM   #15
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Translate what?
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Old 6th October 2013, 06:40 PM   #16
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The Ayumi text is in Japanese.
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Old 7th October 2013, 07:44 AM   #17
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I used Google Translate to get through it, a lot of the text are math anyway, so you should have no difficultly understand them. But basically, Ayumi's model building process relies on electrical equivalent circuits, KCL and Child-Langmuir law unlike Koren's phenomenological approach. Ayumi's pctube program also uses a curve fitting technique similar to what you are doing with the Excel Solver routine.
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Old 9th January 2014, 07:08 AM   #18
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Quote:
Originally Posted by jazbo8 View Post
I used Google Translate to get through it, a lot of the text are math anyway, so you should have no difficultly understand them. But basically, Ayumi's model building process relies on electrical equivalent circuits, KCL and Child-Langmuir law unlike Koren's phenomenological approach. Ayumi's pctube program also uses a curve fitting technique similar to what you are doing with the Excel Solver routine.
Hi jazbo8,

I always use the Bing Translator

This translator give good results but it is for the math I need a translator ...
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Old 9th January 2014, 08:11 AM   #19
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Quote:
Originally Posted by jazbo8 View Post
Here is Ayumi's 6LU8 model vs. the datasheet. Ayumi's model building process is described here. The key is not to use the Koren parameters...

Click the image to open in full size.
This is the kind of accurate curves I like to have for every pentode or "beam power" tubes. I am not a math crack and I never try making a tube spice model by myself but I think this site will help me to understand how to do it.

This page explain the equivalent circuit of a triode and a pentode :

ayumi.cava.jp/audio/pctube/node47.html#SECTION00952000000000000000 - Translator

This is nice but I wonder if it is possible to get all the necessary data for the formulas only from the datasheet specifications and curves ?

I think the first step for a beginner like me to understand how the tubes models works is experimenting with fictive models and test tube data, just to see what kind of curves they produce. I also need to know more about the "URAMP" function because it is used almost everywhere ...

I think the pentode curves should be very accurate in the upper left where is the 0V knee and the lower right because this is where the tube is really operating in a power amplifier circuit, where pass the AC load line.

Thank you for this link !
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Old 9th January 2014, 09:34 AM   #20
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Quote:
Originally Posted by Alain Poitras View Post
This is nice but I wonder if it is possible to get all the necessary data for the formulas only from the datasheet specifications and curves ?
The data usually comes from the datasheet, but sometimes, the data comes from traced curves from actual tubes, the formulas then try to describe in mathematical terms how to best describe the tubes' properties (not always successful though).

Quote:
I think the first step for a beginner like me to understand how the tubes models works is experimenting with fictive models and test tube data, just to see what kind of curves they produce. I also need to know more about the "URAMP" function because it is used almost everywhere ...
You are being too modest, you are not a beginner uramp(x) = x if x > 0, else 0. I'm not sure if SIMetrix uses it though, in any case, the Ayumi pctube library contains all the models in SIMetrix .MOD format, so you can use them directly.

Quote:
I think the pentode curves should be very accurate in the upper left where is the 0V knee and the lower right because this is where the tube is really operating in a power amplifier circuit, where pass the AC load line.
That's actually the hardest part - around the knees, as shown by Robert in this post.

Great to see you back on the forum!
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