Tone Alchemy Bias Pro guitar amp tube bias meter and probe set - complete!

This is a build of the open source Adurino bias meter project. It’s the coolest bias meter there is, by far. It allows you to see all of the data points for both tubes at once, including plate volts, current draw, watts, % of max dissipation, and match. Has options for all popular octal tube types and you can add your own User defined tube profiles. You can also calibrate and fine tune the accuracy through the "Tools" menu.
All of the info is available on the Tone Alchemy GitHub site, as well as instructions on how to build your own. I do not own the intellectual property. I just think it's incredibly cool!
This is a custom hand-built item, and there is no warranty or returns. Includes TubeDepot Bias Scout probes and switched USB power cable.
It works great, but it’s a serious profess tool, so you need some knowledge and skill to use it correctly. See all the info by searching "Tone Alchemy Bias Pro"

From the website:

BiasPro introduces professional-grade data integrity and safety features not found in standard DIY alternatives.

🛠 Core Functionality

• Dual Probe Measurement: Simultaneous real-time monitoring of Tube A and Tube B.
• True Plate Dissipation: Calculates power (Watts) and dissipation percentage based on the specific tube type chosen after the splash screen.
• Screen Current Correction: Implements industry-standard math to subtract estimated screen current, ensuring the displayed bias represents true Plate dissipation, not just Cathode current.

💾 Robust Data Integrity

• Checksum Protection: The EEPROM data includes a computed checksum. If the memory is corrupted or a new chip is installed, the system detects the error and automatically restores safe default values, preventing dangerous behavior.
• Safety Clamps: The Calibration Menu now prevents users from accidentally setting dangerous values (e.g., setting a shunt resistor to 0.0Ω or a voltage scaler to 0), effectively "clamping" entries to safe, realistic ranges.
• Profile Store Protection: Your custom tube profiles are validated on both save and load. A malformed entry (for example a blank name) is rejected rather than written, so a bad edit can never silently wipe your saved profiles back to defaults on the next power-up.

🛡️ Safety & Reliability

• Active Over-Voltage Monitor: While in Live Bias mode, the plate voltage is checked on every measurement cycle; if it exceeds the configured limit the interface locks and displays a red "LOCKOUT" warning until the voltage falls back into the safe band. (The lock, once tripped, persists across screens until released.) This automatic check runs only in Live Bias mode — it is not active on the Calibration screen, even though that screen shows a live voltage. During calibration, rely on your DMM and your own judgement (see the Calibration Guide warning below).
• Safety Hysteresis: The system requires a voltage drop of 50V (hysteresis) before resetting the safety lock, preventing rapid toggling near the limit.
• Input Debouncing: Advanced state-machine logic eliminates switch "recoil" and bounce, ensuring the cursor never jumps unintentionally.
• Sensor-Glitch Rejection: A failed or corrupted ADC read (for example from an EMI burst) is flagged invalid rather than trusted. An invalid reading can never release an active voltage lockout, and Live Bias mode holds the last good measurement instead of momentarily flashing 0 V.
• Flicker-Free Display: Every screen — including the red VOLTAGE LOCKOUT alert — uses incremental redraw, so critical readouts stay rock-steady instead of strobing.
• Centered, Stacked UI Layout: Selection screens (Tube Select and Profile Manager) feature vertically stacked, horizontally centered text elements with balanced line spacing for improved readability.

⚙️ On-Board Calibration

• Software Calibration: Shunt resistance and Voltage Divider scaling can be adjusted via the screen menu and saved to EEPROM. You do not need to edit the source code to calibrate the unit. Edits save automatically when you advance to the next field or leave the screen — there is no separate "save" step — which also minimises wear on the EEPROM.
• Live Voltage Feedback: While adjusting the Scale or Shunt fields in Calibration mode, the screen displays a live, non-blocking computed plate voltage (refreshed every ~350 ms) for the active probe. This allows you to match the calibration to your DMM readings in real time.