I am learning LTSpice and I wanted to model up the amp I built to play with it and learn more about how to use LTSpice.
So I am attaching the schematic I built it from. And the models I could find for the tubes. It uses a D3A in triode mode. I found a D3A triode model but it only references 3 pins in the model file. My schematic is using A,G1,G2,G3,K( or C as it is in the model files). I also found the Pentode model file for the D3A and it is missing G3.
So what should I do? And why is there a triode model anyways? I get that it is being used as a triode but why not include all the pins and connect it as you really would and then there is no need to worry about it being in triode mode.
I don't understand how you can use a model that does not have all the pins you need to connect.
I will have more questions but lets start here.
So I am attaching the schematic I built it from. And the models I could find for the tubes. It uses a D3A in triode mode. I found a D3A triode model but it only references 3 pins in the model file. My schematic is using A,G1,G2,G3,K( or C as it is in the model files). I also found the Pentode model file for the D3A and it is missing G3.
So what should I do? And why is there a triode model anyways? I get that it is being used as a triode but why not include all the pins and connect it as you really would and then there is no need to worry about it being in triode mode.
I don't understand how you can use a model that does not have all the pins you need to connect.
I will have more questions but lets start here.
Attachments
Quite often a dedicated triode model for a triode connected pentode will be more accurate. Just use a triode symbol in the simulation but connect as in your schemeatic in real life. Example attached.
Thanks for the example. But if the tube model is accurate it seems you should be able to hook it up using a pentode model and it would be the same. I am not arguing with you just trying to understand why if the triode model is accurate why wouldn't the pentode model be?
It depends on how the model was generated. Some pentode models are derived from the triode connected curves so they work as expected in a simulation when you connect g2 to the plate. Note that none of the pentode models include g3, so you need to use a tetrode symbol (g3 is often not available for external connection, and when it is there is very little data available).
Also, no model is 100% accurate. Pentode models typically are worse at low plate voltages (around the "knee").
Also, no model is 100% accurate. Pentode models typically are worse at low plate voltages (around the "knee").
Last edited: