LTSpice Modeling Of Vacuum Tube Amplifiers & Output Transformers 

It takes a few hours (days...) to get the hand-of-it but than after that, you can buzz these schematics out in 30 minutes or less. Playing with the values and running simulations is a lot of fun and it doesn't cost anything. Hope you enjoy it.

Hi Mark, Ever since I have seen your message I have looked for the file and link to the transformer parameters I showed in the video and I can't find it. I know I have it somewhere. As soon as I find it and the link where I got it I will reply to you again with the link.

The Koren Tubes file is just a file included in the same directory as the LTSpice file so there is actually no installation. If you have trouble finding any of these files let me know and I can forward to you as they are all free and I assume no restrictions about sharing with each other. I am also willing to share my amplifier files that I draw up. I don't know how to post them for free download so I would need an email address and I will be happy to forward anything I have to you. Thank you for your kind words. This part of my hobby and life is very rewarding much like amateur radio was decades ago where we shared common interests and passions and knowledge for electronics.

Thank you. I had a program called Micro-Cap many years ago on floppy. I will check it out.

I honesty don't know where I found that datasheet on the transformers. I have been asked for it several times before . I have searched for it multiple times and have it somewhere on my PC that I can not find. So much for having good data and then can't find it... If I ever do find it again, I will post a link to it.

@@ElPasoTubeAmps I found something here, www.diyaudio.com/forums/tubes-valves/181578-spice-transformer-model-spreadsheet.html not quite the same. Thanks for the reply.

@@CraigHollabaugh That looks like some of the same data and I like their Spice model. Thanks...

It's primarily used for solid state. The fact that it can be used for vacuum tubes is because of a few guys like us that have taken the time to make models of the tubes, like Norman Koren, and share it. I have never used the Spice group of simulations programs for tubes until now. I really like LTSpice - much easier for me then PSpice. As for designing our own - I think all any of us do nowadays is select circuits or parts of circuits from well known designs and implement them in our builds. By coincidence, last night I was studying a Mullard 20 watt design and it was very much like the McIntosh design used in the MA230. I think everyone has plagiarized each other circuits since the beginning.

Yes, the LTSpice program is very powerful and is used for solid state equipment. We are fortunate that it can also be used for vacuum tube equipment if the Norman Koren or Aymui library of vacuum tube models is also downloaded and copied into the directory where the LTSpice program is located. You can down load it for free at the link below. It is a fantastic program based on the Spice circuit simulator program developed at UC Berkeley. There are other Spice based programs like PSpice which has a free download also that is a student version. The student version is functional with a limited library of models (I do not know if it will run the vacuum tube models or not) and a limited amount of nodes in the model. Usually, the PSpice student program is sufficient for most projects. I used is successfully when I worked for Lockheed at WSMR in the 1990's. www.analog.com/en/design-center/design-tools-and-calculators/ltspice-simulator.html?gclid=EAIaIQobChMImM6u8a-C3QIVTLnACh0iGQMfEAAYASAAEgJM_fD_BwE

ElPaso TubeAmps Wow! I have a mystery Amp from '76? (SS Earth Producer) I have no schematic, can't cross-reference the power transistors - not too worried, I'll just put the Peavey's in without blowing anything up? - but I've been wondering how many different transistors would do different tones. With Ltspice I could find out. Thanks!

Here are some links to library files that will have the 6L6 in it. Not sure if there is a model for the original metal 6L6 but there are lots of other models for the 6L6GC. www.normankoren.com/Audio/Tubemodelinstr.HTM Here is a link for Ayumi tube models www.angelfire.com/electronic/funwithtubes/Spice_lesson_04.html Hope this helps.

There are several things that are important. First, name your Koren file somthing like this: Koren_Tubes.inc - you need that .inc on the end of the file. Secondly, you have to call that file in your LTSpice schematic. Use this statement: .lib Koren_Tubes.inc Third, you must call the tube name exactly as it is in the Koren file. Your Koren file must be where LTSpice can find it. I put it in the same directory as LTSPice. Send me your email and I will send you some LTSpice files that will (hopefully...) work for you so you can see. TheAudioShop@SBCGlobal.Net

Look for Norman Koren web site. This may help. www.normankoren.com/Audio/Tubemodspice_article.html There is also a Ayumi set of files you might want. I don't see them as any better and they take longer to run but, what the heck? If you can't find them after a good search, I can send them to you (I think that is legal...) if you email me direct. TheAudioShop@SBCGLobal.Net

www.linear.com is where you get LTSpice. I believe this is where I got the tube library models. www.normankoren.com/Audio/Tubemodspice_article.html

Thanks man! Appreciate it...

Very nice - Thank You. Lots of models to work with.

Benjamin, Thank you. I can find it easily at ayumi.cava.jp/audio/tubemodel_3.20_win.zip and it unzips easily but I can't figure out how to put it into a file like the Koren tubes and call it as a library. I try calling each tube individually but it I can't get it to work. I suppose I could copy each one into a folder but that seems too laborious and I am sure there is an easier way. Can you help?

The Ayumi models are trickier in that there isn't a single library for all of them, and that they require a bit of editing to work in LTSpice. I decided to just create a library you can add, with all of the models "fixed" for LTSpice already. This should make them easier to use. Here's a link to the zipped up library file: www.dropbox.com/s/0uhqqvdnqpq03qu/Ayumi_Tube_Model_Library.zip?dl=0 Just unzip it in a folder LTSpice can access, use a standard .inc statement to include the library, add the appropriate symbol for the tube type you want, and then edit the value field to the name of the subcircuit given in the library. The name of subcircuit is usually just the tube type.

A few other pointers, there are pre-triode strapped models for various pentodes, beam power tubes, tetrodes, etc. USE THEM. The simulations are faster and more accurate. For a triode, you would just include a triode symbol, but for any pentode, tetrode, beam power tube, etc, regardless of the number of grids, you have to use the tetrode symbol. The little readme file I wrote has more information, plus a complete list of all the tube types available, given as the exact string you want to enter in the value field when using that particular tube model.

I have been trying them and what I have had to do so far is include each tube individually in the schematic but when it runs it turns out really bad so I suspect I am not including another file in the directory that is necessary. Is there any way to put all of these files in one folder so they can be called very simply as they are in the Koren tubes with a .lib statement?

Great... Thanks Benjamin. I just sent you a message concerning what you fixed above. I will download it and try it out. Many Thanks. ..

I remember Dune. I believe Spice came from those huge worms and it made their eyes blue and lips red, if I remember correctly. I don't think LTSpice can be used to create any algorithms but I could be wrong. You get it free from a really reliable source so you might want to check it out, www.analog.com/en/design-center/design-tools-and-calculators/ltspice-simulator.html#