Tube Single-Ended and Push-Pull power stage calculator - critique invited - Page 1
Forum section: electronics / projects

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: February 10, 2022, 03:43:24 am
content: Over the past few weeks I worked up a spreadsheet which will draw SE and P-P plate curves for a pentode or triode used in single-ended or push-pull configuration. Once load with points on the plate current curves, including max plate dissipation power, it will take into account the bias voltage used the screen voltage used and create the I-V charts for it.This is a short description of it:https://imgur.com/a/Ya9ZtuwI sent it to Tristan (u/calinet6 on Reddit) to host the file so that others can try it out. It was created in LibreOffice 7.3 but works in OpenOffice and probably Excel, too. Tristan is hosting the ss for the 6L6 but I have two more for the KT88 both in non-ultralinear and ultralinear mode.Here is his link:https://www.trisweb.com/files/P-P_Calc_6L6.odsClick Edit Document to make it operable.I invite anybody to critique this spreadsheet and post comments here regarding any shortcomings or possible additions or corrections that may be make it better. Feel free to suggest tubes for which you would like to see entered into the calculator.I have three examples of it using the 6L6, KT88 in non-ultralinear mode and the KT88 in ultralinear mode. I will probably do more. The cells which are to accept tube data from the user are the GREY cells. All others are calculated. The output power and distortion figures it calculates are based on the method used by Steve Bench. [EDIT: these methods were originally documented by Langford-Smith in the RDH4 but I cannot, at the moment put my finger on them] In fact, the idea and initial structure of the ss was inspired by him but has been extensively modified and grown from that.The dependence of the curves on screen grid voltage, the plate curves are adjusted from the entered raw data from published/measured plate current curves according to the voltage given on the screen grid. A voltage higher than that on the original curves will make the curves swell upward. A lower voltage will make them shrink down. The amount of this growth/shrinkage is determined by a 2nd order-polynomial that is found by interpolating data also given in the published charts. For instance the 6L6 curves published by RCA include a set of curves which show the plate current at Vg1 = 0 for various Vg2 voltages. I have included this chart as well so you can see what I used. The 2nd order polynomial is found by using the plate current figures from these curves at a fixed plate voltage and Vg1 voltage and fitting a 2nd order curve through them. This way the spreadsheet can self-adjust for the Vg2 to calculate composite curves and power/dist figures at any screen voltage.One thing I have NOT done is to confirm what it calculates experimentally. That would require me measuring the plate current data for a couple of samples on the bench and seeing how they perform in a circuit compared with what comes out of this calculator, I may get around to that sometime when the weather gets warmer.This calculator is given under the Attribution, Non-commercial, Share-alike license. Of course, should the calculator be copied, distributed or used for a derivative work I want the Basin Street Design name and its copyright message preserved.Check it out and LMKWYT

author: alexanderbrevig
author_rank: Frequent Contributor
timestamp: February 10, 2022, 07:15:35 am
content: Looks like nice work but why do you use Comic Sans!?Makes it look not trustworthy.Fonts and presentation matters

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: February 10, 2022, 06:41:07 pm
content: Quote from: alexanderbrevig on February 10, 2022, 07:15:35 amThanks but as for the font, free to change it to anything you want.