• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

ECC82 cathode voltage question


As far as I can see, this calculator doesn't take the input impedance of the next stage (if there is one) into account. For practical purposes that impedance is the value of the grid resistor of the next stage. For AC (so for signal) that impedance stands parallel to the load resistane of the stage (so if the load resistor is 100K and the grid resistor of the next stage is 330K, the AC load becomes about 77K (1/100K + 1/330K = 1/Rac).