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2 layers100 × 61 mmInput, the printed circuit board in 3D

An open source audio interface

Size
100 × 61 mm
Copper layers
2
Thickness
1.6 mm
Parts
122
Nets
97
Pads
383
Tracks, vias
929, 201
Pours
1
Routed
Yes
KiCad
KiCad 10.0 (file 20260206)
Created
8 Apr 2025
Updated
25 Sep 2026

Overview

Input 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 100 × 61 mm with 122 parts on 97 nets, routed with 929 tracks and 201 vias.

It is built around the INA1650IPW, OPA1637DGK and OPA1641AID, with the THAT5263, BAV99 and BSS138 among its other parts. Its parts include 38 resistors, 33 capacitors, 14 diodes, 9 connectors and 7 switches.

Main components

6

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

122
QtyValueFootprintReferences
14100nFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC15, C16, C19, C20, C22, C23, C24, C25, C26, C27, C28, C29, C30, C31
101kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR4, R21, R22, R23, R24, R25, R26, R27, R28, R29
10LEDLED_SMD:LED_0805_2012Metric_Pad1.15x1.40mm_HandSolderD1, D2, D3, D8, D9, D10, D11, D12, D13, D14
52kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR30, R31, R32, R33, R34
410Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR6, R7, R35, R36
41k2Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR9, R10, R15, R20
41uFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC1, C6, C18, C21
422pFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC2, C3, C4, C5
4510Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR16, R17, R18, R19
4SolderJumper_2_OpenJumper:SolderJumper-2_P1.3mm_Open_RoundedPad1.0x1.5mmJP1, JP2, JP3, JP4
2100kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR8, R12
2100pFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC10, C11
210uFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC12, C13
210uFCapacitor_SMD:CP_Elec_5x5.4C32, C33
21MResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR13, R14
2220pFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC7, C14
247uFCapacitor_SMD:CP_Elec_6.3x5.8C8, C9
24k7Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR1, R2
25kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR37, R38
26k81Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR3, R5
2BAV99Package_TO_SOT_SMD:TSOT-23_HandSolderingD4, D5
2SolderJumper_2_BridgedJumper:SolderJumper-2_P1.3mm_Bridged2Bar_RoundedPad1.0x1.5mmJP5, JP7
2VTVS19ASMFDiode_SMD:D_SMFD6, D7
1100Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR11
11000uFCapacitor_SMD:CP_Elec_8x10C17
148V_PHConnector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_VerticalJ5
15263Connector_PinHeader_2.54mm:PinHeader_1x06_P2.54mm_VerticalJ6
15263_GPOConnector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_VerticalJ7
1AUDIO_OUTConnector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_VerticalJ9
1BSS138Package_TO_SOT_SMD:SOT-23Q2
1Conn_01x04_PinConnector_PinHeader_2.54mm:PinHeader_1x04_P2.54mm_VerticalJ1
1GAIN_0openmic:DPDT_SWSW3
1GAIN_1openmic:DPDT_SWSW4
1GAIN_2openmic:DPDT_SWSW5
1GAIN_3openmic:DPDT_SWSW6
1INA1650Package_SO:TSSOP-14_4.4x5mm_P0.65mmU1
1INST_SWopenmic:4PDT_SWSW2
1INST_TPTestPoint:TestPoint_Pad_D1.0mmTP2
1IN_ENopenmic:DPDT_SWSW7
1LINE_INST_N_TPTestPoint:TestPoint_Pad_D1.0mmTP6
1LINE_INST_P_TPTestPoint:TestPoint_Pad_D1.0mmTP5
1LINE_TPTestPoint:TestPoint_Pad_D1.0mmTP1
1MIC_N_TPTestPoint:TestPoint_Pad_D1.0mmTP4
1MIC_P_TPTestPoint:TestPoint_Pad_D1.0mmTP3
1NCJ10FI-H-0Connector_Audio:Jack_XLR-6.35mm_Neutrik_NCJ10FI-H-0_HorizontalJ2
1OPA1612AxDPackage_SO:SOIC-8_3.9x4.9mm_P1.27mmU5
1OPA1637Package_SO:VSSOP-8_3x3mm_P0.65mmU6
1OPA1641Package_SO:SOIC-8_3.9x4.9mm_P1.27mmU2
1OUT_BIASConnector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_VerticalJ8
1OUT_N_TPTestPoint:TestPoint_Pad_D1.0mmTP7
1OUT_P_TPTestPoint:TestPoint_Pad_D1.0mmTP8
1THAT1580Package_DFN_QFN:QFN-16-1EP_4x4mm_P0.65mm_EP2.1x2.1mm_ThermalViasU4
1THAT5263Package_DFN_QFN:QFN-24-1EP_5x5mm_P0.65mm_EP3.4x3.4mmU3
1TRS_SIGConnector_PinHeader_2.54mm:PinHeader_1x03_P2.54mm_VerticalJ3
1TRS_SWopenmic:4PDT_SWSW1
1XLR_SIGConnector_PinHeader_2.54mm:PinHeader_1x03_P2.54mm_VerticalJ4

Questions

How big is the Input PCB?

It measures 100 × 61 mm and has 2 copper layers, 1.6 mm thick.

What parts does the Input use?

122 parts, built around the INA1650IPW, OPA1637DGK, OPA1641AID and THAT5263. 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 Input KiCad files?

From the oliverpaddock/OpenMic repository on GitHub, at the commit this page was made from: the board is hardware/pcb/prototypes/input/v1/input.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 Input 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).

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