Valve/Tube Design - Drawing a Loadline & Calculating Cathode Resistor. Part 1.

[@richardhansen469]

Thanks, this is one of the best explanations I've seen. Because it shows how to determine both resistors. Load lines have been frustratingly hard for me to grasp. What would be really cool, is to combine this video along with an actual breadboarded 6SN7 tube where you can demonstrate the current and voltage measurements with the resistors. A beginner like me can then see how the theoretical process connects to the actual resulting circuit. Very nice.

[@diabolicalartificer]

I shall try & do that for you. TFW.

[@richardhansen469]

@@diabolicalartificer What would be the resulting final schematic with all voltages and resistors shown is generally the goal I would think. So a beginner (like me) can relate the derived schematic to the completed graph markup one does. To eliminate all confusion, for example seeing that the 300 volts on the graph would be the voltage going into the anode resistor, not at the anode itself (one example of how this number always confused me as to where it winds up in the circuit). I never realized finding the cathode resistor needed to be computed using the grid voltage curve, on and on. Wow this is finally beginning to make sense. So many books seem to make assumptions about what the reader knows. I want to learn this basic process, to the point of annotating the graph while simultaneously annotating a schematic, I think that would finally lock it in for me!

[@ianmorgan6104]

Thanks Andy, I’m going to watch this several times later👍

[@diabolicalartificer]

No wuckers me old duck, hope it helps.

[@Luckiestmanalive-bb1mi]

Thanks, for this. It is a complicated process so I've been using online loadline calculator at vtadiy to check the operating point of the tubes in my amplifier. Have you tried it?

[@jahmahrahdesafilli6268]

Great, Thanks for doing this again, it's starting to make a bit more sense now. Just a quick question if I may, Can You put some currant at the maximum plate voltage? Say in Your example the load line was raised to 5ma at 300v (on a max 300v transformer) Would You HAVE to use a higher voltage transformer? (when the load line is 0ma at say 500v). I hope I explained it ok. I would appreciate any help You could give Me. Best Wishes Jahmahrah