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Old 5th December 2010, 04:49 AM   #41
iko is offline iko  Canada
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Tube spice models
A little while ago, just for fun, I trained some neural networks (theoretically universal function approximators) on tube curves, then extracted the parameters out of the neural net as a long function, and used that in ltspice to model a few tubes. After considerable effort, I'm back at using curvecaptor to model tubes. Good enough for rough planning, and I wouldn't trust any better models anyway. At the end of the day it's still the real tube in a real circuit that finalizes the design, for me anyway.
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Old 5th December 2010, 06:05 AM   #42
DualTriode is offline DualTriode  United States
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Quote:
Originally Posted by ikoflexer View Post
A little while ago, just for fun, I trained some neural networks (theoretically universal function approximators) on tube curves, then extracted the parameters out of the neural net as a long function, and used that in ltspice to model a few tubes. After considerable effort, I'm back at using curvecaptor to model tubes. Good enough for rough planning, and I wouldn't trust any better models anyway. At the end of the day it's still the real tube in a real circuit that finalizes the design, for me anyway.
Hello,
For rough planning or what if thinking SPICE is the perfect tool.
This circuit may never be built but it helped me understand what I know. I have been thinking of a new RIAA pre amplifier that uses a cascode input stage. I picked a 6DJ8 out of the sky because there are good models out there and it started life as a RF cascode tube. I found that the top tube really does shield the bottom grid from Miller capacitance and the bandwidth is huge, this is not news. Seeing the output helps the understanding. Also noted the gain can be huge, like 90 plus, also not news. What is news to me is that a resistor can be put in series with the bottom triode bypass capacitor and the circuit gain can be adjusted to any value over a wide range suitable for moving coil to moving magnet.
This may never be built in the real world but it does works in SIM.
If it is built the computer will go back to work testing the results.
DT
All just for fun!
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Old 5th December 2010, 05:01 PM   #43
jackinnj is offline jackinnj  United States
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Tube spice models
I haven't used Eureqa for tubes, i have used it for light dependent resistors --

The program allows you to use several operators, + - x /, log, exp plus trig. You can also select which type of error to optimize. It will give you a very good fit for one series. You can separate the data sets and get good fits for multiple series.

The hyper expensive version of Multisim (Pro Professional) allows curve tracing, but you can do it by exporting the data from the grapher to Excel and creating a series of XY plots. Use a "piecewise linear source" for the grid voltages, and the function generator in triangle mode generator for the plate. No reason you couldn't do this in LTSpice.
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Old 5th December 2010, 09:02 PM   #44
jackinnj is offline jackinnj  United States
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Tube spice models
This is what it looks like:

Click the image to open in full size.
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Old 22nd November 2011, 07:22 PM   #45
kees52 is offline kees52  Netherlands
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Default multisim errors

Hi there

I have troubles with simulation models in multisim.

maybe someone can help what it means these errors, I am not yet as good
with making models.

I have include the models for use it have a lot in them, also the difficult ecc99, 6n6p etc, and the power penthodes and triodes.

I made a snip from screen with the errors, it is in multisim tryout.
Attached Images
File Type: gif ScreenHunter_02 Nov. 22 21.03.gif (13.4 KB, 218 views)
File Type: gif ScreenHunter_01 Nov. 22 21.01.gif (8.2 KB, 218 views)
Attached Files
File Type: txt triode_nh.txt (23.5 KB, 51 views)
File Type: txt tetrode.txt (16.4 KB, 23 views)
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Old 25th November 2011, 08:47 AM   #46
PGDO is offline PGDO  Netherlands
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Default Eureqa

If been trying out the Eureqa program for modeling tube curves. Once you get the hang of the program and have the right settings the outcome is quite usable.

Not all solutions found work well in spice, especially the "big size" formulas tend to give problems (I used MicroCap).

Best results so far were obtained when using the "Akaike" Fitnes metric.

I used Excel to obtain the points needed for Eureqa.

Attached are the Excel file and some pictures, I used an 300b curve.
Attached Images
File Type: jpg Eureqa Moddeling task.jpg (127.8 KB, 205 views)
File Type: jpg Eureqa results.jpg (184.3 KB, 181 views)
File Type: jpg Eureqa Enter Data 1-75%.jpg (126.4 KB, 70 views)
Attached Files
File Type: zip 300b fit1.zip (22.4 KB, 24 views)

Last edited by PGDO; 25th November 2011 at 08:54 AM.
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