The full toolbox.
37 calculators across 8 categories. Search by tool, tube type or keyword, or filter by group.
Tube Database
Offline specs, pinout, equivalents and published operating points for popular audio tubes. Look up µ, gm, rp, maximum ratings and heater data -all from the datasheet, available without an internet connection.
Open toolTube Pinout Viewer
Socket diagrams for 2,400+ tube types including rare and obscure types not in the main database. Tap any pin to highlight it. Covers noval, octal, loktal, rimlock, UX and top-cap bases.
Open toolPlate Curves & Load-Line Analyzer ⭐
The app's flagship tool. Plot anode characteristic curves for triode, pentode, or ultralinear operation; draw the load line; set the Q-point; and read off voltage gain, output power, clipping margin and estimated 2nd harmonic -all from your own values.
Open toolSubstitution Guide
Find compatible replacements for nearly 2,000 tube types. Each substitute is graded Exact / Drop-in / Rebias / Caution with notes on sonic differences and heater current -the detail that prevents overloading a mains transformer.
Open toolTester Settings (TV-7 & TV-2/U)
Knob-by-knob settings for TV-7 and TV-2/U military testers covering 2,600+ tube types. Lists every control position -Fil V, Plate, Screen, Grid, Range -plus the pass/fail threshold.
Open toolResistor Color Code
Decode 4-band and 5-band colour codes, or enter a value to see which bands to look for. Also handles SMD 3-digit, 4-digit and EIA-96 codes. Shows value, tolerance and the E-series the part belongs to.
Open toolResistor Combo Finder
Enter a target resistance and the app finds 1–3 standard E-series resistors (series, parallel, or mixed) that combine closest to it. Tap any suggestion to see the circuit. Optionally restrict to values already in your parts drawer.
Open toolSum Resistors
Calculate the equivalent resistance of any series or parallel network. Add as many resistors as you need.
Open toolVoltage Divider
Forward mode: enter Vin, R1, R2 -get Vout, current and dissipation in each resistor. Reverse design mode: enter the source and target voltages -the app finds the nearest standard E12/E24 pair and shows the Vout you'd actually get. A live schematic updates as you type.
Open toolStepped Attenuator Designer
Design a switched-resistor volume control. Choose series, shunt or ladder topology; set A (log), B (linear) or custom dB-per-step taper; pick an E-series. Get the full schematic, a step-by-step dB table and a shopping parts list -per channel, so double for stereo.
Open toolLED Resistor Calculator
Calculate the current-limiting resistor for single LEDs, series strings or parallel arrays. Choose from LED-colour presets (red, green, blue, white…) or enter your own Vf / If. Shows the theoretical value, the E24 part to actually buy, and the resistor's power rating.
Open toolCapacitor Code Decoder
Decode EIA 3-digit numeric codes (104, 472…), text markings (4u7, 100n), and colour bands. Gives the value in pF, nF and µF simultaneously, plus tolerance and working voltage when the marking carries an EIA voltage letter.
Open toolCapacitor Combo Finder
Find 1–3 standard capacitors that combine to a target value you don't have. Series, parallel and mixed -ranked by error. Capacitors add in parallel and divide in series, so the maths is handled for you.
Open toolSum Capacitors
Calculate the equivalent capacitance of any series or parallel network.
Open toolCapacitor Charge & Energy
Enter capacitance and voltage to get charge (Q = CV) and stored energy (E = ½CV²). Useful for sizing PSU reservoirs -and for understanding how much energy a charged amplifier capacitor is holding before you touch it.
Open toolRC Time Constant
Enter R and C to get τ = RC, the 63.2% charge time, and the 5τ full-charge time (~99.3%). Essential for coupling capacitor and bypass capacitor design.
Open toolCapacitive Reactance
Calculate Xc = 1 / (2πfC). Enter frequency and capacitance to find the AC impedance of any capacitor.
Open toolSum Inductors
Calculate the equivalent inductance for series or parallel coil networks.
Open toolAir-Core Coil Designer
Single-layer and multilayer winding calculator using the Wheeler formula. Enter diameter, length (and depth for multilayer) then either the number of turns or the target inductance -get whichever you didn't enter, plus the wire length to cut.
Open toolInductor Energy Storage
Enter L and I to get E = ½LI² -the energy stored in a choke's magnetic field.
Open toolRL Time Constant
Enter R and L to get τ = L/R and the 5τ settled time -the current-rise figure needed when designing choke-input supplies.
Open toolInductive Reactance
Three-way solver: enter any two of impedance (Z), inductance (L) and frequency (f) to find the third. Z = 2πfL.
Open toolPower Transformer Designer
Design a mains transformer from the core you have. Choose EI, C-core or toroid; set Bmax or k-factor; add every secondary you need. Get VA rating, turns per volt, turns and wire gauge for every winding, and a window-fill warning when the wire won't fit.
Open toolOutput Transformer (OPT) Calculator
First-cut OPT design for single-ended or push-pull stages. Enter Zp, speaker impedance, output power and lowest frequency. Get turns ratio (Np:Ns), minimum primary inductance, air-gap thickness (SE), and a DC + signal flux check to catch core saturation.
Open toolGapped-Core Choke Designer
Design a PSU filter choke on a gapped core. Three modes: solve for turns, inductance, or both. Calculates air-gap, shim thickness, wire gauge, window fill, DC resistance, voltage drop and copper loss -with a saturation warning when the flux exceeds Bmax.
Open toolTransformer Turns Ratio
Enter primary turns, secondary turns and primary voltage to get the turns ratio and secondary voltage.
Open toolImpedance Transformation
Calculate the primary impedance seen by the tube from primary turns, secondary turns and speaker impedance. The core calculation behind matching a tube's plate impedance to a loudspeaker.
Open toolZener Shunt Regulator
Design a zener shunt regulator. Enter supply voltage (with variation), zener voltage, max load current and minimum zener current. Get the series-resistor window -not a single value, because Rs must handle both full-load and no-load -plus dissipation and efficiency.
Open toolAdjustable Regulator (LM317/LM337)
Set the output voltage of an LM317 (positive) or LM337 (negative) regulator. Enter Vin, target Vout and R1 to find R2; or enter R1 and R2 to find the actual Vout. Also calculates IC dissipation and estimated junction temperature -the part people skip.
Open toolPower Calculator
Four-mode solver: enter any two of P, V, I, R to find the other two using P = VI, P = I²R and P = V²/R simultaneously.
Open toolLC Resonant Frequency
Enter L and C to get resonant frequency fr and angular frequency ω. Covers tank circuits, filters and RF work.
Open toolRC / RL Filter
Calculate the –3 dB cutoff frequency for passive first-order low-pass or high-pass filters. Enter R and C (or R and L); get fc, τ and the circuit drawn for the filter type you chose.
Open toolDecibel Converter
Convert between dB, voltage ratio and power ratio -the 20 log and 10 log scales side by side. Exactly where level-calculation mistakes happen.
Open toolOhm's Law
Three-mode solver: enter any two of V, I, R to find the third and the power dissipation. The tool every other calculation starts from.
Open toolConnector Pinouts
Pin diagrams for common audio and power connectors -USB, HDMI, VGA, RS-232, XLR, RCA, DIN, IEC and more. Tap a pin or row to highlight it.
Open toolWire Gauge Converter
Enter a size in AWG, SWG, mm or mm² to get the equivalent in all other systems, plus cross-sectional area, current rating and resistance per metre -the figure needed when winding transformers or calculating cable voltage drop.
Open toolFrequency & Period
Two-mode converter: enter frequency to get period, or enter period to get frequency.
Open tool