This calculator allows you to trace the anode characteristics graph, and to compute and tune loadline and operating point of various vacuum tubes.

It considers both reactive loads and resistive load.

You can:

- choose among most common vacuum tubes (I am slowly adding more),
- set the operation modality, among
**ultralinear**,**pentode**, and**triode**mode, - set
**Single-Ended**or**Push-Pull**configuration - set the load type as
**reactive**or**resistive** - set the Power Supply V+ voltage, the screen voltage, the screen tap, the quiescent bias current.
- set the output headroom

The calculator:

- plots the
**anode characteristic graph**, for the chosen operation modality, - plots the
**reactive loadline**for reactive load, - plots the
**DC and AC loadlines**for resistive load, - highlights the
**operating point**, - highlights the needed
**output headroom**, if set, - estimates the
**grid bias voltage**, - estimates the
**expected power**at the load when max Grid Voltage is the maximum displayed, when max Grid Voltage is 0, when operating in Class A or A2, and at the selected output voltage headroom. - estimates the
**Harmonic Distortion (HD)**in the operating range corresponding to the selected output headroom

**Did you buy my book? Remember to leave a review on amazon!**

**Select a Tube:**

Operating mode: | PP/SE: | ||

V+ (V): | Grid Bias Voltage (V): | ||

Quiescent Operating Point: |
Iq(mA): Vq(V): |
Output Power (W): | |

Load (Ohm): | HD%: |
| |

Next stage AC Impedance (Ohm): | |||

Screen Voltage (V): | |||

UltraLinear tap (%): | |||

Out. headroom (+/-V): |

If you are not familiar with loadlines, their purpose, and their use, I suggest you checking my guide: Section 3.2 (for resistive loadlines), Section 4.1.3 (for reactive loadlines), and Section 4.2.2 (for AC loadlines).

The underlying model and equations, for tracing anode characteristics curves, are those discussed by Norman Koren, in his web site.

Very useful calculators! Thanks for your hard work. Any chance of adding 6l6gc and perhaps 6v6 to the list?

Hi I recently added 6l6g. 6v6 will be added in the future

6V6 is also there

Kindly add 6BK5 to your choices

6BK5 is now available!

Very helpful calculator. Which tubes are you planning to add? How might I help?

Thanks for appreciating it. I recently addedd 6l6g, kt77, 6h30, kt150.

Do you have any suggestions?

Adding 6SQ7, 6888, and 7AK7 would be useful for me, thank you.

Thanks. I added them to my todo list

6SQ7 and 6888 and 7AK7 are ready in the calculator

Grazie e buona salute a te!

Could you add 6GM8? Thank you.

Done!

I appreciate your work here! Perhaps you should do a Patreon? I would certainly donate to this project. I use 6sl7 and 6sn7 quite a bit for preamp and phase inverter duty. Would love to 6v6 on here as well. Thank you!

6V6 just added. 6sl7 and 6sn7 are on waiting list 😉

6sl7 and 6sn7 are now available as well.!

Great job! This thing is so useful. Is there a chance to add 6AK6, ECL82 and ECL86?

Thanks in advance, brother.

I will try when back from vacation.

Merry Christmas!

Looking forward to it. Merry Christmas to you too!

Done! Check it!

Great! Thanks! This is definitely going to in handy. Because the 6AK6 can be used as a power valve, could you also add it with a reactive load? Thanks in advance .

Done!

You, sir, are great! Grazie mille 🙂

It is now possible choosing resistive or reactive load for every tube, in the Universal Loadline Calculator.

How difficult would it be to implement parallel valves? Could it be as simple as maybe a tick box to double the current scale and push the load line down?

Hi, as I explained in a post in Loadline calculator for power stages, when you attach a load to n parallel tubes, each tube simply sees n-times the load. The calculator computes the loadline of of a single tube. To use this calculator to compute your loadline, with parallel tubes, simply specify n-times the overall load.

Hi Giuseppe, I don’t know if it’s easy to do but having some double triodes on reactive loads would be a hell of and add-on ! I’m thinking 6SN7 push pull, 12AU7 push pull… Maybe it is possible since you have the models? That would be nice!

Your simulator is so much quicker than opening Orcad or another spice simulator.

Thanks for the amazing work !

The Universal Loadline Calculator now allows switching between resistive and reactive load for every tube.

Thanks Giuseppe for this amazing calculator. I was just checking it against a 2A3 data sheet and they match beautifully. Any chance of adding the JJ 2A3..?

2A3-40 JJ is now available.

nice tool … great job!!! Any chance of adding the 6550 and kt120 tungsol ?

Thanks!!!!

They are in the pending list. Hope to be able to add them soon.

6550 added!

KT120 still pending

KT120 done as well!

You are the best ! Thank you very much!! Amazing tool !!

🙂

Great job! My congratulations! I would also like to see EL86, 6AH6 and other, less common tubes, such as A2134.

Best regards!

Hi,

I’ll put them in the list. Hope to be able to add them soon.

Thanks for your feedbacks.

Thanks! Add 12E1 if possible)

Best regards!

12E1 just added

Many thanks!)

6AH6 added!

Thanks!

EL86 just added

Many thanks!

A2134 ready as well

Fantastic)

😉

Hello, is the Max Power RMS or peak Watts?

Hi,

it is a rough approximation of the output power when producing a sine wave ranging up to the saturation of the valve (for instance when reaching Vg=0) along the loadline.

More details are given in section 6.1.1 of my guide here: https://www.vtadiy.com/book/chapter-6-step-by-step-design-of-a-push-pull-tube-amplifier/6-1-design-of-the-power-stage/

Hope this is useful.

Hello Giuseppe, greetings from Greece

This online curve calculator is a really nice work, congrats!

Can you please add GM70 & GU50 to your list with positive grid curves

Keep going with all good fortune

Cheers

Thanks!

Addedd to the todo list … the list is becoming long 🙂

I just added GM70.

However, I did not find positive curve datasheet for this triode. Do you have it?

GU-50 added as well

Hi can you please add 6GU7 6CG7 12BH7

Hi, I added them to the todo list as well. Be patient 🙂

12BH7 is now available

6GU7 is also there

… and 6CG7 is ready … also with positive grid

Dear all,

thanks for using this calculator and thanks for suggesting additional tubes.

The pending list of tubes that will be added now includes:

ECL84, ECL85

kt120

EL86, 6AH6, A2134, 12E1

GM70, GU50

6GU7 6CG7 12BH7

45, 101D, 205D

Hope to be able to add them all in a couple of weeks.

Looking forward to. Thank you very much!

Is it possible to add 6K6GT to the list as well? Thank you!

Sure!

I added it to my pending list.

Thanks

6K6GT is now ready

Added 6AQ8 (ECC85)

12AT7 (ECC81) and 6J5, are now available in the calculator.

6J5 can also be tested with positive grid (however double check limiting values in the official datasheet http://www.r-type.org/pdfs/6j5.pdf )

Very nice tool Giuseppe!!! When I compare tubes it seems for example EL34 use 0V as Control Grid voltage when this calculates Power so Anode Current comes lower and Anode Voltage higher than for example 6L6GC which use +15V Controd Grid voltage. I just bought your Kindle book which I hope explains how it is possible to use CG positive values…

Sorry Giuseppe! Now the previous comments did open for me to read and you have already pointed to chapter where it is explained.

Perfect! 🙂

thank you for your calculator. can you please add 6AQ5/6005/EL90

Thanks. I added them to my todo list

Grazie tante per questa cosa.

Grazie a te 🙂

Done! Try it. 🙂

Hi,I want 6N7/6N7P/6H7C tube, Could You Add it?

Added to my todo list

And 807 tube

Hi, note that 807 is available since some days.

However, I still need some time for 6N7/6N7P/6H7C. There are others head in the list 🙂

Thanks I seen.

6N7/6N7P/6H7C are Same Tube ,6N7 is US Model，6N7P is China Model，6H7C is Soviet Model. It’s use for the low power Class-B PP.

6N7 added!

Please add 829B tube, thanks Vince

Added to my, now long, todo list 🙂

829B was already available. Hwever I took the opportunity to refine the model.

Hello, Giuseppe! If possible, please add E180F and EL803S. I will be very grateful!

In the todo list … be patient 🙂

Thanks! 🙂

Thanks for 6JN6)))

Buongiorno Giuseppe, complimenti per il tuo lavoro!!! Potresti aggiungere la 845? per la 211 e 845 sarebbe interessante qualche valore di griglia positiva!

Grazie

Hi Feliciano, addedd to my pending list.

Thanks!

Tra l’altro, considera che per la 211 ci sono già le curve con valori positivi di griglia.

By The way, note that 211 already has positive grid values available.

845 Ready!

Hello, Giuseppe! Is your pending list empty?)

Hi Dimitri,

Currently I have these in my pending list (sorted according to request date):

829B, E180F, EL803S, EC8020, E55L, 5881,Ck6336

Best regards

Very interesting list. Thank you very much!

This is so useful. thankyou! Any chance you could add 6au6? Thanks again.

Thanks!

Addedd to my pending list