# Talas One — Open Hardware Condenser Microphone

A large-diaphragm condenser microphone designed for professional audio recording. Fully open hardware: schematics, PCB layouts, BOM, and assembly documentation published under CERN-OHL-W-2.0.

![Assembled prototype](photos/prototype_assembled.jpg)

## Overview

Talas One is a dual-PCB condenser microphone based on the Alice OPA circuit topology by DJJules:
- **Preamp board** — OPA1642 low-noise operational amplifier, balanced XLR output
- **Hex inverter board** — TC4584BF-based voltage multiplier providing bias voltage for the condenser capsule

The dual-PCB architecture means if one component fails, you replace that component — not the whole microphone.

## Project Status

**Prototype assembled — debugging in progress.**

Both PCBs have been fabricated (PCBWay) and hand-assembled with SMD and through-hole components. The prototype does not produce audio yet — first-revision debugging is underway. This is documented openly as part of the design process.

> The hex inverter KiCAD project in this repository is a partial reconstruction. The complete design files from the fabricated board are being recovered and will be uploaded shortly. The fabricated board photos and gerber files are included.

## Repository Structure

```
hardware/
  preamp/                  # OPA1642 preamp — complete KiCAD project
  hex-inverter/            # Hex inverter PSU — KiCAD project (WIP, see note above)
  components/              # Custom KiCAD symbols and footprints
  gerbers/                 # Production files (as sent to PCBWay)
bom/                       # Bill of materials with sourcing links
docs/
  assembly-guide.md        # Step-by-step build instructions (in progress)
photos/                    # Prototype and PCB photos
LICENSE                    # CERN-OHL-W-2.0
```

## Photos

| Preamp PCB | Hex Inverter PCB | Assembled Mic | Body + Capsule |
|:---:|:---:|:---:|:---:|
| ![preamp](photos/pcb_preamp.jpg) | ![hex](photos/pcb_hex.jpg) | ![assembled](photos/prototype_assembled.jpg) | ![body](photos/mic_body_detached.jpg) |

## Circuit Design

Based on the Alice OPA topology (DJJules, published on Instructables and GroupDIY forums):
- **Capsule**: t.bone SC-600 large-diaphragm condenser (34mm, gold-sputtered)
- **Preamp**: OPA1642AIDR — ultra-low noise, low distortion JFET-input op-amp
- **Bias supply**: TC4584BF hex Schmitt-trigger inverter configured as charge pump, generating ~60V DC bias from 48V phantom power
- **Output**: Balanced, transformer-less, via standard XLR connector

## Bill of Materials

See [`bom/`](bom/) for the complete BOM with component values, part numbers, and sourcing links.

Key components:
| Component | Part | Role |
|-----------|------|------|
| Op-amp | OPA1642AIDR | Low-noise preamp |
| Hex inverter | TC4584BF | Bias voltage generation |
| Capsule | t.bone SC-600 | Large-diaphragm condenser |
| Resistors | MFS series (metal film) | Signal path |
| Capacitors | Nichicon / Vishay | Filtering, charge pump |

## Tools Required

- Soldering station with fine tip (for SMD work)
- Stereo microscope or magnifying lamp
- Multimeter
- Oscilloscope (for debugging — recommended)
- Standard screwdrivers (body assembly)

## Design Software

All electronic design files use [KiCAD](https://www.kicad.org/) (open source EDA).

## License

Hardware design files are licensed under **CERN Open Hardware Licence Version 2 — Weakly Reciprocal (CERN-OHL-W-2.0)**.

See [LICENSE](LICENSE) for the full text.

## Acknowledgments

- **DJJules** — Alice OPA circuit topology (Instructables, GroupDIY, JLI Electronics)
- **DIYPerks** — inspiration for the "build a studio mic for cheap" approach
- The [GroupDIY](https://groupdiy.com/) and [micbuilders.com](https://micbuilders.com/) communities

## Author

**Nikola Milovanovic** — [Talas Group](https://talas.music)