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26th March 2010, 04:45 AM  #1 
diyAudio Member
Join Date: Nov 2005
Location: SoCal

Help with circuitmaker Pentode model
Hello,
Can anyone help me figure out how the numbers in bold are determined? *Vacuum Tube Tetrode (Audio freq.) .SUBCKT X7199P 1 6 3 4 B1 2 4 I=(((URAMP((V(7,4)/20)+V(3,4)))^1.5)/1206)*ATAN(V(1,4)/10) B2 7 4 I=((URAMP((V(7,4)/20)+V(3,4)))^1.5)/2562 C1 3 4 5.0P C2 3 1 0.06P C3 1 4 2.0P R1 3 5 5K R2 2 4 2.5MEG D1 1 2 DX D2 4 2 DX2 D3 5 4 DX D4 6 7 DX D5 4 7 DX2 .MODEL DX D(IS=1.0P RS=1.0) .MODEL DX2 D(IS=1.0N RS=1.0) .ENDS X7199P Thanks! 
27th March 2010, 04:28 PM  #2 
diyAudio Member
Join Date: Nov 2005
Location: SoCal

Nobody

27th March 2010, 07:05 PM  #3 
diyAudio Member
Join Date: Oct 2005

I wonder what a X7199P is.
Tried to plot the curves in LTSpice with your model, but did not make complete sense to me. You may want to look at: Norman Koren: Improved vacuum tube models for SPICE, Part 1 How to "paint" your own tube models: Model Paint Tools: Trace Tube Parameters over Plate Curves, Interactively Svein. 
27th March 2010, 11:39 PM  #4  
diyAudio Member
Join Date: Nov 2005
Location: SoCal

Quote:
This is a working model for circuitmaker which I copy pasted. LT Spice models might be a little different. Any chance you know how amplification factor is determined for a pentode? I noticed it is used in all pentode model equations (including Norman Koren's). Pentodes are transconductance devices, so determining amplification factor without a specified load seems impossible to me. Perhaps it explains in his article, but I didn't catch it. The paint your curves program looks really interesting. But, it's probably going to take a while for me to get it working properly on my computer. Then I'll have to figure out how to translate it's spice output into circuitmaker. Eventhough the circuitmaker model is not the most accurate, it would certainly be easiest if I could just figure how those numbers were determined. It would be easy to create more models. Just copypaste the model, change the name, those mysterious numbers and the capacitance values. I've already figured out how to model triodes on circuitmaker (thanks to the help of others in this forum), just having problems with the pentode model. 

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