Tube Bias Calculator II

Enter info in blue and click any 'Calculate' button

Select Tube Type: Enter Plate-to-Cathode Voltage: DC volts (plate voltage minus cathode voltage)

 

Tube Max Design Dissipation = watts  100% Pa

Class A Fixed Bias   70% Cool = DC milliamps    80% Average =    90% Max Safe Dissipation =
Class AB Fixed Bias   50% Cool = DC milliamps    60% Average =   70% Max Safe Dissipation = *
Cathode Bias   85% Cool = DC milliamps    95% Average =    100 % Max Safe Dissipation =
*Merlin Blencowe believes up to 85% is OK for Class AB Fixed Bias Amps

Tube Dissipation Using Cathode Resistor Voltage Drop

You must enter Tube Type and Plate-to-Cathode Voltage above before calculating Tube Dissipation.

Enter Number of Tubes that share a cathode resistor:  

Enter Voltage Across Cathode Resistor: DC volts Voltage drop across the cathode resistor.

Enter Cathode Resistor: ohms  Cathode resistor ohm value.

  

Total Cathode Current = DC milliamps   = Voltage Across Cathode Resistor / Cathode Resistor.

Total Plate Current = DC milliamps  = Cathode Current minus approximate screen current of 5.5%.

Plate Current per Tube = DC milliamps  = Total Plate Current / Number of Tubes.

Plate Dissipation per Tube = watts   = Plate Current per Tube x Plate Voltage.

Plate Dissipation per Tube % = % Plate Dissipation per Tube % = Plate Dissipation per Tube / Tube Max Rated Dissipation.

If your tube is a triode (or dual triode with both triodes used) your plate current is milliamps, your plate dissipation is watts and %.

Tube Dissipation Using Plate Current

Use this calculator when you measure the actual plate current. You must enter Tube Type and Plate-to-Cathode Voltage above before calculating Tube Dissipation.

Enter Plate Current: DC milliamps

 
    
 

Plate Dissipation = watts  = Plate Voltage * Plate Current.

Plate Dissipation % = %  = Plate Dissipation / Tube Maximum Rated Dissipation.

 
Note: You must re-calculate after changing values by clicking any Calculate button. Tube Type and Plate-to-Cathode Voltage must be entered for all calculations.