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

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

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/ 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 (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 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 and micbuilders.com communities

Author

Nikola Milovanovic — Talas Group