VPP (V) 
RL (kΩ) 
vacuum tube voltage and currents


  1. Enter your plate supply voltage and plate load resistor value.
  2. Click the green button.
  3. Pick a desired DC operating point on the red load line.
  4. Enter its plate current and grid voltage from the graph.
  5. Enter the input impedance (AC load) of the next stage.
  6. Click the recalculate button.
  7. Read the cathode resistor value from the top of the calculator.
  8. Observe the updated green AC load line, which shows the extent of guitar signal swing relative to the DC operating point.