Finding a tool

Three ways to reach any of the 37 calculators:

• Search on the home screen -type a tool name, a tube type, or a keyword ("load line", "12AX7", "colour code").
• Browse by category -the eight category icons at the top.
• Recents & favourites -tools you've used appear first; tap ★ to pin the ones you use constantly.

Entering values

Type SI prefixes directly -every numeric field understands them, which is far faster than counting zeros. A dot or a comma both work as the decimal separator, and results update as you type (there is no "calculate" button).

• 4k7 or 4.7k → 4.7 kΩ
• 100n → 100 nF
• 2M2 → 2.2 MΩ
• 10u or 10µ → 10 µF
• 470p → 470 pF

"Solve for" -one tool, several directions

Many calculators have a Solve for selector at the top. Enter the quantities you know, choose the one you want, and the app rearranges the maths for you.

Example -Ohm's Law: choose Voltage, enter current and resistance, and you get voltage. Choose Resistance instead, enter voltage and current, and you get resistance. Same tool, three directions. Each tool's detail page states how many modes it has.

Reading the results

• The bold figure is the main answer; the lines under it are the supporting numbers that matter in practice (dissipation, total current, error against the target).
• Amber and red panels are warnings: dissipation exceeded, current too high, core saturating. Read them before you build.
• Standard-value suggestions round to the E12/E24/E96 series, so you can buy what the app recommends.
• Schematics are drawn from the values you entered and redraw as you change them.

Language

Switch language any time from the top navigation. Tube electrode names and technical database entries stay in English in both languages -those are the international terms printed on every datasheet, so leaving them alone keeps the app consistent with the documentation you're working from.

⚡ Safety

Valve circuits run at lethal voltages. B+ rails of 250–500 V are routine and large amplifiers exceed 1,000 V. Reservoir capacitors hold a dangerous charge long after the power is off -always discharge and verify before touching a circuit.

Treat the app's output as a design starting point, not a substitute for measurement and experience. Real components deviate from theory, and tubes in particular vary 10–20% between samples of the same type.

FAQ

• Does it need internet? No -everything ships inside the app, so it works in a workshop with no signal.
• Where does the tube data come from? Manufacturer datasheets, plus Koren parameter sets shared and refined by the valve community.
• How accurate is it? The Koren model is empirical; a few percent deviation from datasheet curves is normal and fine for design work.
• Why are electrode names in English even in Vietnamese mode? Plate, Grid, Cathode and the rest are the international terms printed on every datasheet.