# OhmNote: Electronics Tube Amp — Transformers & Valve Pinouts

> Transformers & Valve Pinouts (iPhone/iPad app by Sang Truong.)

- Source: https://appshunter.io/ios/app/ohmnote-electronics-tube-amp/id6799597672 (this page in markdown: same URL + `.md`)
- Developer: [Sang Truong](https://appshunter.io/developer/6799597675)
- Category: Utilities, Productivity
- Price: Free with in-app purchases
- Age rating: 12+
- Requires: iOS 15.6 · 29 MB
- Languages: American English
- Released: 2026-08-20
- Data updated: 2026-09-18
- User reviews in markdown: https://appshunter.io/ios/app/ohmnote-electronics-tube-amp/id6799597672/reviews.md

## What is OhmNote?

OhmNote is the electronics calculator that finally takes vacuum tubes seriously.

Whether you're designing a valve amplifier, winding a transformer, restoring vintage gear, or just learning Ohm's law, OhmNote puts many precise, beautifully crafted tools in your pocket - and it all works completely offline, with no ads and no account.

From a quick resistor color-code lookup to plotting a load line and winding your own output transformer, it's the rare toolkit that covers everyday electronics AND the deep tube-amp math most apps ignore.

BUILT FOR VACUUM-TUBE ENTHUSIASTS

Tube Analyzer - plot the load line, set the Q-point, and read gain, set bias, estimate distortion and more in real time
Tube database - specs, operating points and applications for hundreds of tubes
Tube pinouts - clear base diagrams at a glance for thousands of tubes
Tube substitution - find compatible replacements and equivalents
Tester settings - ready-to-use setups for popular tube testers

TRANSFORMERS & MAGNETICS

Output transformer (OPT) designer - turns ratio, primary inductance, air gap and saturation check
Power transformer designer - VA, turns-per-volt, every winding and its wire gauge
Gapped-core choke designer for power-supply filtering
Air-core inductor (Wheeler) - turns ↔ inductance, both directions
Transformer ratio & impedance, plus wire gauge (AWG ↔ SWG ↔ mm)
Inductive Reactance of coil or transformer - inductance ↔ impedance ↔ frequency

EVERYDAY ELECTRONICS

Ohm's law & power - solve for any value
Resistor color code (4/5/6-band + SMD) - read or generate
Capacitor code decoder, LED resistor, voltage divider
Series/parallel resistors, capacitors and inductors
Reactance, RC/RL time constants, resonant frequency
dB converter, frequency ↔ period

POWER & SIGNAL

Adjustable regulator (LM317 family) with heat & heatsink check
Zener regulator designer
Stepped attenuator (log volume control) designer
RC/RL passive filters with drawn schematics
Resistor & capacitor combination finder
Connector pinouts - USB, HDMI, VGA, RS-232 and more

WHY YOU'LL LOVE IT

Solve forward OR reverse - enter what you know, get what you need
Smart SI-unit input - just type 4.7k, 100n, 1M…
Instant results as you type
Fully offline - no internet required
No account, no ads, privacy-first
Gorgeous light & dark themes
Available in English, Vietnamese, Spanish, French and German

OhmNote is made for guitar and hi-fi amp builders, audiophiles, ham radio operators, repair techs, students and working engineers - anyone who wants fast, trustworthy answers without the clutter.

Download OhmNote and build with confidence.

Terms of Use (EULA): https://ohmnote.com/terms
Privacy Policy: https://ohmnote.com/privacy

## Pricing and in-app purchases

Base price: Free.

**Subscriptions**

| Subscription | Price | Period |
| --- | --- | --- |
| Hàng tháng | $2.99 | per month |
| Hàng năm | $14.99 | per year |

**One-time purchases**

| Purchase | Price | Type |
| --- | --- | --- |
| Gói trọn đời | $39.99 | one-time |



## Version history (last 4 releases)

### 1.0.4 — 2026-09-12

Support Russian Language 
Enhance Tube Analyze Tool
Enhance UI for more tools, separate into two mode basic and advanced for easier using

### 1.0.3 — 2026-08-25

Enhance UI for Tube-Analyzer
Support updating data file
Support Auto Updates

### 1.0.2 — 2026-08-25

Add more tubes information
Enhance the Tube-Analyzer tool
Enhance all inputs to follow SI standard

### 1.0.1 — 2026-08-20

No release notes.

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-09-18.*