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**(suppressor tied to cathode) 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:**Check full list of available tubes

Operating mode: | PP/SE: | ||

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

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

Load (Ohm): | |||

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

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. However 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)))

E180F and EL803 added

Many many thanks!

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

6AU6 just addedd and available to be used

Ciao Giuseppe,

could you please also add 12AY7 and ECC808? Thanks for all you do, it’s really very useful

Antonio

Hi Antonio,

Thanks! Added to my to do list. Be patient 🙂

12AY7 is now available.

Thank you so much Giuseppe!

ECC808 available as well

Great! I’ll wait, no problem. Good Easter

Hi, can you add 3A5 (DCC90) with sections is parallel? And 4P1L triode strapped.

Added to my todo list! Thanks

Anything? Regards

Hi Tomislav,

here is my pending list: EFL200/PFL200 , 2AY7 ECC808, 3A5 (DCC90), PX25, 300BXLS, T100, 12AT7/6072, 5902/6p30b, 6n16 and 6n17, 6C41, 6U8A, 6528.

Just a few, before your 3A5. Be patient 🙂

Thanks.

3A5 is now available

Thank you!

4P1L is ready as well. However, be carefull. In my model, triode mode is with G3 connected to to ground. I saw some curves, obtained with curve tracers, where 4P1L triode mode was plotted using G3 connected to anode, resulting in much higher current. Take this into account, if you compare my curves with those.

Hi Giuseppe.

Why I cannot set both Iq and Vq using my “own” values?

If I set Iq, the tool automatically calculates Vq and related Grid Bias Voltage or if I set Vq, the tool automatically calculates Iq and related Grid Bias Voltage.

My desire is to put my pair of Iq and Vq values, then obtaining Grid Bias Voltage from tool.

Thanks.

Hi Federico,

Once you fix the load and V+, then Vq and Iq are dependent one from the other becouse the Ohm Law: Iq=(V+-Vq)/load.

So, if you modify one of the two, the other follows from the Ohm Law and cannot be chosen arbitrarily. The result is that Vq and Iq are constrained to move along the loadline.

The calculator in addition computes the Grid Voltage needed to obtain the chosen pair (Vq,Iq).

Hi Giuseppe, you are right!

I often forgot the role of load line..

Nifty tool thank you !

Could you please add 12AT7/6072

Added to my pending list

12AT7 and 6072 (12AY7) are available

Hi. Thanks for that. It’s really helpful solution for designing and understanding valve amps.

I appreciate your job.

Is it possible to add there 6c41 tube? I have a datasheet if you need.

Regards

Thanks!

Added to my todo list. If you already have a datasheet, it would make things easier to me.

Hi,

6c41c is now available to be tested

THANK YOU GIUSEPPE.YOU SAVED US FROM A LOT OF CALCULATION TIME.THE TUBE 6U8A IS A VERY HANDY TUBE COULD YOU PLEASE ADD IT TO YOUR LIST?

Thanks a lot for appreciating my effort. I added the 6U8A to my (increasing 🙂 ) todo list.

6U8A (both triode and pentode sections) finally addedd to the calculator.

could you at 6sk7 6ba6 6j7 6sj7 6au6

Hi Arash,

note that 6sj7 and 6au6 are already available.

I added the others to my pending list.

Hi Giuseppe,

Hope you’re doing well.

I have a question, some tubes (like PCC88 and 6N7) show positive grid voltage curves.

I am a little confused by these, does this mean that these are still usable?

The reason why I am asking, is that the ECC88 for example doesn’t show these, while it’s basically the same tube (different heater voltage).

The result is that the calculated output power is a lot higher??!!??

Positive grid voltages should be used according to the guidelines in the datasheet. When in my graphs I show positive grid curves is because these are shown also in the datasheet. However, for using them carefully check the datasheet. Input impedance changes significantly with positive grid values, so circuits should be carefully designed for this.

For what concerns output power. In the last version of my calculator, I show various values, corresponding to output voltage swing along the loadline up to: max grid value displayed, grid equal to 0, class A/A2, and power at the specified headroom.

Thanks.

So practically for a Class-AB push-pull does this means I have to look at the grid equal to 0 (= g1), or is it also possible those valves to a positive grid?

Positive grid is possible both in Class A2 and AB2. Soecifically, class A means that the tube does not cut-off. It corresponds to a headroom around the operating point that does not arrive to tube cut-off. This might happen within negative grid (Class A) or positive grid (Class A2). In Class AB (negative grid) and AB2 (also positive grid), in turn one of the two tubes might cut-off, for a limited time, when delivering high output power.

Thanks, and it just depends on the tube if they can handle positive grid voltages?

So why isn’t there a positive grid for the ECC88 but there is for the PCC88 ?

To give a practical example, let’s put the PCC88 in PP mode, with V+ of 150V, reactive load of 15k and bias current of 8mA

According to this calculator, I should get 2.53W out of a PP PCC88, is that correct? Or am I just missing something?

Hi,

In fact there was an imprecision in the PCC88 model. The Philips PCC88 datasheet does not mention the possibility of positive grid. So I removed the option of choosing positive grids for this model.

When I built it I used the E88CC as basis, which is very similar and also allows positive grid values.

Now it should be fine.

Giuseppe! can you add 811A ? thaks

Added to may, now veeeery long, pending list.

I have been quite busy during last month and the pending list is now very long.

Can you do JJ’s 6V6S? While it is VERY similar to the 6V6GT it does have higher voltage tolerance as well a high plate dissipation.

Added to my long pending list

Dear firends,

recentely I have been very busy so my list of tubes to add became very long. Sorry for taking so long to satisfy you requests.

Currently my pending list contains:

ECC808, 3A5, 4P1L, PX25, 300BXLS, T100, 5902, 6p30b, 6n16, 6n17, 6C41, 6U8A

6528, 6sk7, 6ba6, 6j7, 6Y6, 811A, 2E22, 6dq6b, 6gw6, 6V6S

Hi Giuseppe!

Can you please add 811A?

Hi Arash,

It is in my pending list … there are a few haed of it still waiting … pe patient 🙂

Hi,

811A is now available.

Giuseppe Amato , how are you ? With a 807 tube , 4200ohm load, 350V 75mA. Do you think is a good point of work ?

Hi,

if you want Class A, probably yes. Elsewhere, I think you might need higher voltage and lower quiescent current.

Hello Giuseppe! Thanks for Your jobe)

Can You add 6BX7, 6AH4 and 6CK4 tubes in yours fantastic collection?

Best regards, Dmitry.

Added to my todo list.

Thanks

Many thanks!

Hello Giuseppe! Thanks for Your job !!!!!

6E5P , 6E6P , 7721 or D3A ?

Hi,

Addedd to my long pending list

Thanks you.. and Could be that when i look E180F in triode mode , dont run correctly.. For example, i put 200v y then figure 100v or 150 !! and the current too is diferent to i put.. Santiago.

Hi,

I was not able to reproduce the problem. Can you send me a screeshot?

However, note that Vq and Iq cannot be chosen arbitrarily. They depend one fron the other and the operating point MUST stay on the loadline.

Giuseppe , i was in Load Resisitve , not reactive.

it was my mistake

Ok! Perfect!

Hello Giuseppe, Thank you so much for your excellent work. I notice when a certain tube is selected, the calculator starts up with defaults to a certain V+ and Iq. Are these the optimum operating conditions you or the data sheets suggest ?

Hi Joseph,

Default values are, in most cases, taken directly from datasheets. Optimal values depend on specific design and preferences.

Thank you, Giuseppe