Solvers for triodes

An online collection of DC solvers for circuits based on triodes ECC81-82-83-88 and a far more powerful free PC app, including more tubes, more circuits and small-signal results

December 2022 – download PC app V1.8

The Windows PC application now offers 28 solvers in total, among which several clever circuits designed by John Broskie in https://www.tubecad.com

Download the application for Windows PC

Usage stats

Since January 2020, you performed more than 31 000 actions, and about 13000 in 2022. The most activated solvers are the gain stage +DC-coupled cathode follower (C4) for about 1/3, the basic common-cathode gain stage (C1), the cascode SRPP (C8), the Phase inverter, fixed bias cathodyne (C5) and the true cascode (C6).

See Usage stats. Stats are available too in the PC app.

Web resources

Among the many web sites (there was a lot to my surprise) I visited by fall 2019, I found particularly interesting these links

My contribution: a collection of triode solvers

This web site and the PC application are my contribution to the “tube community”, offering a set of solvers able to compute the operating points (DC bias) of the basic low-level circuits that are found in all tube amplifiers: gain stage, cascode, cathode follower, phase inverter, etc. The online library is limited to a few solvers and the DC state, whilst the PC app also delivers small-signal estimations for most of his solvers.

I programmed them for people who already are aware of tube design but who may feel uncomfortable with true simulation Spice-tools. One solver is needed per circuit. Luckily, the small number of circuits variants allows this simpler approach.

They are not perfect, they are in no case real circuits, and I am not liable for any wrong designs you may create after them! And never forget that playing with tubes is very dangerous because of the required high voltages!

Norman Koren’s modeling

All solvers use the modelling of triodes proposed by Norman Koren in the 2000’s, as described in http://www.normankoren.com/Audio/Tubemodspice_article.html taking advantage of his “new equations” and the parameters he indicates for the triodes 6DG8 (ECC88), 12AU7 (ECC82) and 12AX7 (ECC83). For other tubes, I took parameters from Spice models found on the Web.

I had also considered other models proposed by Dempwolf und Zölzer and Cohen and Hélie which take into account grid current. But as basic stages normally do not operate with grid currents, I decided to not implement them; in addition, my understanding is that they are based on very little experimental data (only ECC83), and one of them was simply not implementable because of a non documented parameter.

Contact me at tubes @ astefo.com