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2 layers66 × 38.1 mmV2-line, the printed circuit board in 3D

An open source audio interface

Size
66 × 38.1 mm
Copper layers
2
Thickness
1.6 mm
Parts
55
Nets
50
Pads
171
Tracks, vias
256, 131
Pours
1
Routed
Yes
KiCad
KiCad 10.0 (file 20260206)
Created
8 Apr 2025
Updated
25 Sep 2026

Overview

V2-line is an open-source printed circuit board by oliverpaddock, from the oliverpaddock/OpenMic repository on GitHub, published under the CERN-OHL-S-2.0 licence. It is a 2-layer board of 66 × 38.1 mm with 55 parts on 50 nets, routed with 256 tracks and 131 vias.

It is built around the INA1650IPW, OPA1637DGK and BAV99. Its parts include 21 resistors, 17 capacitors, 9 connectors, 3 ICs and 3 diodes.

Main components

3

README

README.md

OpenMic

OpenMic is an open-source, 2-in, 2-out, usb-c audio interface.

About

Why open source?

Open source audio/music hardware is not scarce, but general-purpose open source audio interfaces for musicians are essentially non-existent. OpenMic brings repairability, transparency, and education to an overlooked corner of music hardware.

You own your hardware. All schematics, firmware, and design files are publicly accessible so you can repair it, modify it, and understand it.

What is OpenMic?

If you aren't familiar with audio interfaces like the Focusrite Scarlett 2i2 or the Universal Audio Apollo Twin, they basically take analog audio - from a microphone, a guitar, a synth, etc. - and convert it into digital audio your computer can use in a DAW like Ableton, Logic, or Audacity. They also convert digital audio from your computer back into analog audio that you can hear through speakers or headphones. Interfaces also typically provide some sort of amplification or volume control on the inputs and outputs.

This is exactly what OpenMic does. Two inputs that can take microphone/line/instrument level signals, outputs for your speakers, and a headphone jack. Plus a few other features like phantom power that are listed in more detail in the Features section.

Block diagram System block diagram

Current Status

OpenMic is currently in the prototyping stage. The circuit has been designed and simulated, and individual systems are being built and tested. View the schematics to see the current circuit design.

Progress will be posted on the OpenMic blog as prototyping continues.

Roadmap

  • Initial design and component selection
  • Simulation for design verification
  • Subsystem prototyping
  • Full board design in KiCad
  • First full v1 board
  • Crowd supply launch
  • Production

Features

  • 2 combo XLR/TRS inputs (mic/line/inst)
  • Balanced TRS stereo line outputs
  • TRS headphone output
  • 48V phantom power
  • Direct monitoring
  • Up to 32-bit/96kHz
  • USB-C bus powered (1.5A) with external USB-C fallback
  • Drives headphones from 32Ω to 600Ω
  • Fully open hardware and firmware

Getting Started

If you want to view/edit KiCAD files, make sure to add the part libraries located in /hardware/libs to your project or globally in your KiCAD instance.


Sponsors

AISLER 

AISLER 

Special Thanks

THAT Corporation

Neutrik

Parts

55
QtyValueFootprintReferences
9100nFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC1, C5, C7, C8, C9, C10, C11, C14, C15
52kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR13, R14, R15, R16, R17
410uFCapacitor_THT:C_Radial_D5.0mm_H11.0mm_P2.00mmC2, C3, C12, C13
4510Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR6, R7, R8, R9
210Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR18, R19
2100Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR22, R23
21kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR11, R12
21k2Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR5, R10
21uFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC4, C6
2330pFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC16, C17
25kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR20, R21
2BAV99Package_TO_SOT_SMD:SOT-23D2, D3
11MResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR4
147kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR1
1ANLGConnector_PinHeader_2.54mm:PinHeader_1x05_P2.54mm_VerticalJ2
1DG1412EEQPackage_SO:TSSOP-16_4.4x5mm_P0.65mmSW1
1GNDConnector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_VerticalJ4
1INA1650Package_SO:TSSOP-14_4.4x5mm_P0.65mmU1
1LEDLED_SMD:LED_0805_2012Metric_Pad1.15x1.40mm_HandSolderD1
1LOWVConnector_PinHeader_2.54mm:PinHeader_1x09_P2.54mm_VerticalJ3
1OPA1612AxDPackage_SO:SOIC-8_3.9x4.9mm_P1.27mmU2
1OPA1637Package_SO:VSSOP-8_3x3mm_P0.65mmU3
1OUTConnector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_VerticalJ9
1OUT_BIASConnector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_VerticalJ8
1PHConnector_PinHeader_2.54mm:PinHeader_1x03_P2.54mm_VerticalJ1
1SW CTRLConnector_PinHeader_2.54mm:PinHeader_1x04_P2.54mm_VerticalJ7
1SolderJumper_3_Bridged12Jumper:SolderJumper-3_P1.3mm_Bridged12_RoundedPad1.0x1.5mmJP1
1TRSConnector_PinHeader_2.54mm:PinHeader_1x06_P2.54mm_VerticalJ5
1XLRConnector_PinHeader_2.54mm:PinHeader_1x05_P2.54mm_VerticalJ6

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Questions

How big is the V2-line PCB?

It measures 66 × 38.1 mm and has 2 copper layers, 1.6 mm thick.

What parts does the V2-line use?

55 parts, built around the INA1650IPW, OPA1637DGK and BAV99. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.

Where can I download the V2-line KiCad files?

From the oliverpaddock/OpenMic repository on GitHub, at the commit this page was made from: the board is hardware/pcb/prototypes/input/v2-line/v2-line.kicad_pcb and its schematic hardware/pcb/main-board/codec.kicad_sch. PCBKit opens the board in the browser, with nothing to install.

Can I use the V2-line design in my own project?

Its repository publishes it under the CERN-OHL-S-2.0 licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).