Free Electronics & Amplifier Tools
Fast calculators built around real repair-bench jobs — for musicians, amp technicians, electronics engineers and anyone who wants the numbers without the guesswork.
Valve Bias Pro for Android
A dedicated valve-amp toolkit with bias calculations, valve and amplifier libraries, multi-valve comparison, saved jobs and workshop references.
Set up, test and diagnose.
Biasing, speaker loads, transformer ratios and the calculations behind common amplifier work.
Valve / Tube Bias Calculator
Calculate target plate current from plate voltage and dissipation, then compare measured valve currents.
Open calculator →Speaker Impedance Calculator
Work out series, parallel and common 2×12 / 4×12 cabinet loads before connecting an amplifier.
Open calculator →Plate Dissipation Calculator
Convert measured plate voltage and current into watts and percentage of the valve’s rated maximum.
Open calculator →Cathode Bias Calculator
Estimate cathode current, plate current and dissipation from cathode voltage and resistor values.
Open calculator →Output Transformer Ratio
Calculate turns ratio, impedance ratio and reflected primary load from measured AC voltages.
Open calculator →Ohm’s Law & Power
Enter any two known values and calculate voltage, current, resistance and power instantly.
Open calculator →Quick bench calculations.
Handy component and circuit calculators for everyday fault-finding, prototyping and repair work.
Resistor Colour Code
Decode a standard 4-band resistor into its resistance value, tolerance and expected range.
Open calculator →Capacitors: Series & Parallel
Calculate equivalent capacitance and convert between pF, nF and µF in one place.
Open calculator →Voltage Divider
Calculate unloaded divider output voltage, current and resistor power dissipation.
Open calculator →Resistors: Series & Parallel
Calculate equivalent resistance for two, three or four resistors in common network arrangements.
Open calculator →Understand the calculation.
Short practical guides that explain the theory, assumptions and workshop context behind the tools.
Valve / Tube Bias Explained
Plate voltage, current, dissipation and the difference between plate and cathode current.
Read guide →Speaker Impedance Explained
4 Ω, 8 Ω and 16 Ω loads, plus series, parallel and common cabinet wiring.
Read guide →Output Transformer Impedance
Turns ratio, impedance ratio and how a speaker load reflects back to the output stage.
Read guide →Ohm’s Law for Electronics Repair
Voltage, current, resistance and power with practical bench examples.
Read guide →Resistor Colour Codes Explained
Read 4-band resistor values, multipliers, tolerances and replacement considerations.
Read guide →Capacitor Values Explained
pF, nF and µF conversion, series/parallel rules, polarity and voltage ratings.
Read guide →Equipment already faulty?
We repair guitar and bass amplifiers, PA, mixers, effects, lighting and selected electronics from our Telford workshop.