Need Vacuum-Tube Circuit Components

First, let me say thank you! CircuitLab is a great idea.

I'm an electronics designer & engineer/technician with ~40 years experience. I'm also a blues-playing electric guitarist (semi-pro) that's been playing nearly as long as I've been involved with electronics.

I currently design and build vacuum tube guitar/bass amplifiers at home for both fun and profit. I also help new tube guitar amp building hobbyists on a number of different forums with help/tips on design & construction.

I desperately want to see vacuum tube components added to the list of available circuit components. This would be a tremendous help in sharing circuit designs/modifications/corrections with other tube guitar amplifier builders/hobbyists on forums and elsewhere.

I can guarantee you'll have a large number of tube guitar amp hobbyist and semi-professional users if vacuum tube related circuit components are available for modeling.



by stratman_el84
February 28, 2012

I came here to post this. Give us some triode and pentode love, please.

by polar_attraction
February 28, 2012

Stratman is right, add tubes to this puppy and you'll be crawling with users.

by cjgrier
February 28, 2012

I think we might be able to make this happen (in time)... Can you guys point me to some sample schematics / articles / etc. for the kinds of things you'd like to be able to simulate? Can you list some specific favorite part numbers? Not promising anything yet, but I'll certainly take a look and see if it looks feasible. Thanks all for the feedback :)

by mrobbins
February 28, 2012

OOH... That would be VERY cool. I have an old reel to reel that I tore apart to convert into a tube guitar amp. 12AX7 pre-amp and 6aq5 ouput tube. It all worked good as a reel to reel, just the rollers were shot etc.. I completely tore the circuit apart and then realized... What do I need to do to ensure the voltages to the tubes are correct. This would be very nice to build a sample amp and test it out on. Mike, PLEASE consider this one. Most of the common amp tube datasheets are available on the web.


by Rick_S
February 28, 2012

Yes I too echo the sentiment.

A ton of classic schematic's here.

This is a typical hobbyist schematic:

Many tube datasheets here:

some common vacuum tube types seen in musical instrument amplifiers 12AX7, 12AY7, 12AT7, 5751, 6V6, 6L6, EL34, KT66, EL84, 5Y3GT, EF86

by tube925
February 28, 2012

Another voice in support of vacuum tubes! I'm mostly interested for music (guitar, bass, mic amp) applications, but I bet there's some RF interests, too. More generally, being able to specify custom circuit components would be nice as well.

by danhuff
February 28, 2012

I have access to SPICE simulation models for some tubes,. Will these examples be useful for CircuitLab's developers?

Coolest. JavaScript. Ever.

by tubegeek
February 28, 2012

Mike: A someone who has worked in pro audio for 35+ years, I'm also adding my plea for tubes to included in component mix. The suggestions by tube925 are a great place to start.

There's plenty of data available online, but I'm not sure how complicated it will be to do models that truly represent the various factors in common circuit topologies.

However, I can guarantee that you'll have a lot of tube audio enthusiasts flocking to your site fore this if you can pull it off!

by Audioguy
February 29, 2012

Just found this site! Wow! Waay better than Multi-Sim! ;) Joined to add my request for some tube simulations. The most popular would probably be typical audio amp and guitar amp circuits.

Glad to be here! Clay

by Fisherdude
February 29, 2012

Hi there to all. Great nice idea that you have created. Indeed Tubes is a must for serious DIY's, so consider that issue seriously if you want to grow. If assistance is needed, I am sure tnere are a lot of us than can assist,



by tubester
February 29, 2012

Gimme some tubes!!! Triodes, pentodes, rectifiers, big ones and little ones.

Great site.


by Gerd
March 01, 2012

+1 on Vacuum tubes as the no 1 most desired feature.

If you can get a 12AX7, 6V6, 6L6, EL34 and EL84 you would cover most of the typical Fender/Marshall/Vox classic guitar amps. The DIY guitar amp community would love it...

Common DIY guitar amp projects would be Fender "Tweed" Champ and Deluxe, Marshall "Plexi" and "18 watt" amps.

by d95err
March 01, 2012

Anyone ever see a basic practice amp built with a 6AQ5 output tube?

As I stated in my earlier post, I had an old reel to reel that had a working amp. Rather than just modding the amp, I thought it might be easier to just do it over because I didn't need the recording portion of the circuit. Anyway, the amp had a 12AX7 and 6AQ5. I see several circuits with a 6BQ5 but haven't found many built around the 6AQ5. The amp also had a 6X4 Rectifier and 5879 (which I think was used for the microphone??) any way, The Tape player played fine with no crackle or unusual noises so I figure the tubes are good.

I did find a micro champ by ALPERN Amplification that used the 6AQ5 but I don't know how to ensure the voltages coming from my transformer will be right because my output is different than what his transformer was.

The bad thing is, I stripped everything except the transformers, the aluminum cased multi-cap and the tube sockets. I pretty much am going to have to build from scratch. I just don't know where to begin.

One last thing, would it be better to go with solid state rectifiers or keep the 6X4?

Any ideas?? This is where having this available here would be great.


by Rick_S
March 02, 2012

Incredible execution of a great idea. This seems like a great educational tool, but it also is incredibly ideal for amplifier/audio related people who have had the hardest time sharing or explaining circuits to people, plus working with someone else in troubleshooting issues. That is why I would also like to throw my support in for the addition of Tubes if it seems feasible.


by biznen151
March 04, 2012

I agree, too, that adding tubes to the design toolkit would really be a monster plus for CircuitLab. I would think (for starters) that a triode tube model (for the purpose of simulation) could be created similarly from how a BJT model works but put in a tube schematic symbol (and for a tube, obviously work at much higher voltages). Grids could be emulated like the base of the BJT, plate could be emulated as the collector, cathode as the emitter. Granted, that's pretty simplified because there are other control grids in a pentode tube that when biased do create special circumstances for that kind of tube - kind of like having other control 'bases' in a BJT (not that that's ever been done in practice). That would have to be separately worked in CircuitLab. But for starters, a triode could be emulated right out of the chute and act like a BJT. Food for thought....

by martywittrock
March 04, 2012

Okay, so I did a little research on this site and someone has already published a tube design - with 12AX7As in it - on CircuitLab about 3 days ago, a member called 'tubester'. Here's the link to his design:

While the circuit itself is practical, it's not capable of being simulated yet. There is another gent who posted to his page that does have a circuit model of a tube itself (based on the amplifying characteristics of the tube and an extended electrical model) eventually someone will take both of these capabilities and develop a model for a 12AX7A tube that can be placed and used in a design.

BTW - I'm interested in this, too, since I play blues on my Les Paul Custom and Fender Telecaster guitars. Appears there's movement by several to make tubes a reality for CircuitLab somewhere down the road...

by martywittrock
March 04, 2012

I to wish for vacuum tube modeling.

Hope it will comes to pass, but realize the work involved.

by vonpostel
March 04, 2012

Tubes? Sure , but do you really want to model the percieved audio quality of tube in comparison with transistor? Not sure how. If that is the case , I nominate the most versatile tube ever - RV12P2000 , just kidding.

by Vaclav
March 06, 2012

Since we probably have quite a few Amateur Radio Ops here, there are a few other tubes that might be appreciated. Especially since they are still available NOS. For instance, 6146B is a transmitter tube, A 12SK7 is an IF or RF amplifier. A 12SA7 is a converter/oscillator tube. A12SQ7 is a detector/1st AF/AVC tube. Sound great if you could do a few to start with.

by Ranzabar
March 06, 2012

thanks for this great place to work. I agree; tubes will make it much more useful for a lot of us. I design tube amps, primarily for guitar, and would love to have a way to draw them like this. Being able to run sims without having to build first would be fantastic. I've been cutting and pasting components! Can I draw a component outside and import it? Adding sim to tubes would be absolutely lovely; thanks agaian.

by guitars48
March 11, 2012

Add me to the Tube requester list!

The list above from Tube295 is a great one to start with: 12AX7, 12AY7, 12AT7, 5751, 6V6, 6L6, EL34, KT66, EL84, 5Y3GT, EF86

I would add 6SN7, KT88, ECC88 and 5AR4 to round it out.


by TAJ
March 12, 2012

Ditto. Tubes would be awesome. Even just symbols without a spice model, would be a great place to start.

by chrisrossi
March 27, 2012

Please add me to the list of those interested in tubes for Circuit Lab. Symbols would be great! Even basic triode and pentode symbols would be very helpful. Simulations would be fantastic - but understandably more complex.


by earthsled
April 14, 2012

Yes, tubes would be nice, but somewhat pointless.

The basic tube circuits, preamps, tone controls, and power stages, have been very thoroughly explored, in every possible topology, single-ended, push-pull, SEPP, Circlotron, etc, etc, etc.

And a lot of what tubes are noted for, the "tube sound", you're (1) Not going to get out of any tube model and (2) Even if you did see choke inductance swings, grid current, tetrode kinks, bottoming and transformer nonlinearities and saturation, you can't hear it in Circuitlab, so what's the point?

So while I'd like to see at least a 12AX7 and 6L6 as models, realize that they're more for pure blue-sky paper exercises than anything else.

by arduinohacker
April 15, 2012

I would probably be motivated to add vacuum tube models if the code were open source. Hint hint.

by chrisrossi
June 23, 2012

Maybe I missed something. Is there a way to upload models to CircuitLab?

by chrisrossi
June 24, 2012

@chrisrossi said:

"I would probably be motivated to add vacuum tube models if the code were open source."

then asked:

" Is there a way to upload models to CircuitLab?"

At present, no, there is no way to upload models directly into CL.

However, in my reply, I assumed you meant models drawn as CL circuits or as expressions that can be used in CL circuits using behavioural sources like @arduinhacker's 12AU7 circuit:

by signality
June 24, 2012


Ah, sorry, I was just saying that if the code were open source the community could make direct contributions to the code, by way of device models, etc... Although, now that I think about it, publishing a spec for writing uploadable device models would be just as good and not require open sourcing the whole project. Then, various niche communities could provide the models of interest to them.

I do understand that you could model tubes using behavioral sources, like above, which is pretty darn cool. For me, though, the real value of this service is being able to bang out a schematic and share it, easily, with the rest of the world. For that, really, we need symbols.

by chrisrossi
June 24, 2012

Actually, I think valve "models" are all subcircuits anyway: SPICE does not have set of parameters that describe valves and so has no .model statement for valves.

The clue is in the name:

Simulation Program with Integrated Circuit Emphasis.

That said, has anyone ever seen any SPICE models for FETRONS?

by signality
June 24, 2012

I don't know if anyone else has seen this on "SPICE simulation of vacuum tubes":

by signality
June 24, 2012

+1 for vacuum tubes. Even if all their non-linearities aren't captured exactly, just having a symbol to work with would be a big plus for guys like me who want to use this to work on old tube amps.

Right now I guess a triode can be roughly approximated using a BJT (as martywittrock suggested above), but I don't know of a way to simulate a tetrode or pentode. Maybe just start with basic symbols for "Rectifier Tube", "Triode", "Tetrode", and "Pentode"?

by ghaws
October 12, 2012

Just to add to my previous post, I notice there are now quite a few symbols that are non-simulatable so why not add tube symbols this way to start - at least we could then draw neat schematics.



by ruffrecords
April 08, 2013

+1 For tubes! Great idea, this would help a lot of people over internet.

by EduBSB
July 13, 2013

+1 for vacuum tubes

by kemitchell
December 08, 2013

+1 for tubes!

by geedeebee
January 06, 2014

+1 from me. it is a big gap and not many providers.

by foadm
January 09, 2014

Happy to add my voice to the call. I agree with ruffrecords' (aka Ian's) comments as one of the things i really like about CL is the nice schematics it produces.



by musicandmeyhem
February 09, 2014

+1, even without simulation

by religiosa
April 23, 2014

@stratman_el84, do you have any experience with rebuilding classic (1960's era) Fender/Marshall amps? I'm interested in trying to DIY one myself but have very little experience with tubes. I was an Air Force radio mechanic but that doesn't include any tube work. Basically, they said, "This is a tube. If you ever see one, RUN!" :-)

by Penglet
May 06, 2014

Not me, i'm getting into it now as an interest with no previous experience. i'm in your situation, self learning from internet sources. good luck

by foadm
May 06, 2014

Thanks, @signality ! I'll check it out.

by Penglet
May 07, 2014

many thanks signality :o)

by foadm
May 07, 2014

I have to add my voice to the many who need simple tube models, just a simple generic triode, dual triode, pentode and a rectifier model would be enough to start. I am tired of trying to simulate with transistor models...

by TeeDaddy
March 16, 2015

This would be an excellent feature addition!

by jcolber2
April 05, 2016

People have been asking for this feature for over 4 years, has anyone contacted the developers directly??

by SeeJayDee
July 17, 2016

Bump! Just wanted to throw my hat in the ring of people who are (still) interested in having some tubes in CircuitLab! A few 12A?7 triodes, some basic power tubes (EL34, EL84, KT88, 6L6, etc.), and some tube rectifiers would be a welcome and much appreciated addition.

by jriggles
April 13, 2017

seems to me as though this isnt an active community and/or user base. no updated content. very poor considering this product has potential

by tom-wesley
May 26, 2017

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