Calculator

Common Equations for Tube Amps & General Audio Electronics

Welcome to the SonicTone calculator. It is intended to be a useful online tool to assist with many common formulae and equations needed when working on tube amps or other audio electronics.

You can enter different value formats, for example:

Warning: Tube amps can contain dangerous and even lethal amounts of high voltage. Working with these voltages can be very dangerous or even fatal, so do not do so unless you are knowledgeable and skilled enough to work on tube amps. SonicTone Amplification is not liable for any damages, loss, injury or death due to the use of this calculator to assist in working on a tube amplifier or any electronics. Use the calculator and its results at your own risk.

Ohm's Law
[V = I x R]
Enter two of the variables to calculate the value of the third variable.
Voltage Divider
[V(out) = V(in) x (R2 / (R1 + R2))]
Enter all three variables and click calculate.
Power
[P = I x V]
Enter the current and voltage values to calculate the power in watts. Entering the max dissipation value in watts will give you the percentage of dissipation achieved.
RC Filter
[1 / 2ΠRC]
Enter the resistance and capacitance values to calculate the value of the cut-off frequency.
Resistance
Enter comma-separated values of resistance to calculate the total resistance. Select the correct configuration in which the resistors are configured.
Parallel Series
Capacitance
Enter comma-separated values of capacitance to calculate the total capacitance. Select the correct configuration in which the capacitors are configured.
Parallel Series
Bias
This calculator utilizes the output transformer resistance to measure the plate current to calculate the bias. Select the correct amp configuration parameters. Enter the B+ voltage and at least one OT primary resistance value and one tube plate voltage value.

Warning: To perform this calculation, it requires measurements of high voltage while the amp is turned on. Working with voltages can be very dangerous or even fatal, so do not do so unless you are knowledgeable and skilled enough to work on tube amps. Please see these reference links for more information on this procedure: Biasing Tube Amps, Biasing an Amp (Part 1), Biasing an Amp (Part 2), How to Bias an Amp.
Output Transformers
This calculator can be used in one of three ways:
  1. To calculate the unknown primary impedance of an output transformer
  2. To calculate the unknown speaker impedance of a secondary tap of an output transformer
  3. To calculate impedance and winding ratios of an output transformer
To calculate the unknown primary impedance, you must enter the voltages applied and transformed on the primary and secondary taps, as well as the known speaker impedance of the secondary tap.

To calculate the unknown speaker impedance of a secondary tap, you must enter the voltages applied and transformed on the primary and secondary taps, as well as the known primary impedance.

To calculate the impedance and winding ratios, simply enter the known primary impedance and the speaker impedance of the secondary tap.

Warning: To perform this calculation, you must apply voltage to the taps of the output transformer and take measurements of what the voltages are on the primary and secondary taps. Working with voltages can be very dangerous or even fatal, so do not do so unless you are knowledgeable and skilled enough to work on tube amps. Please reference this video for more information on this procedure.
B+ Voltage
To estimate the rectified B+ voltage, enter the secondary VAC value and select the type of rectifier used. Results are approximate.

Capacitance Conversion Chart:

Microfarads (uF) Nanofarads (nF) Picofarads (pF)
1uF 1000nF 1000000pF
0.68uF 680nF 680000pF
0.47uF 470nF 470000pF
0.33uF 330nF 330000pF
0.22uF 220nF 220000pF
0.1uF 100nF 100000pF
0.068uF 68nF 68000pF
0.047uF 47nF 47000pF
0.033uF 33nF 33000pF
0.022uF 22nF 22000pF
0.01uF 10nF 10000pF
0.0068uF 6.8nF 6800pF
0.0047uF 4.7nF 4700pF
0.0033uF 3.3nF 3300pF
0.0022uF 2.2nF 2200pF
0.001uF 1nF 1000pF
0.00068uF 0.68nF 680pF
0.00047uF 0.47nF 470pF
0.00033uF 0.33nF 330pF
0.00022uF 0.22nF 220pF
0.0001uF 0.1nF 100pF
0.000068uF 0.068nF 68pF
0.000047uF 0.047nF 47pF
0.000033uF 0.033nF 33pF
0.000022uF 0.022nF 22pF
0.000010uF 0.01nF 10pF
Version 1.3.0
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