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2 layersOpenmic, the printed circuit board in 3D

An open source audio interface

Copper layers
2
Thickness
1.6 mm
Parts
432
Nets
370
Pads
1,687
Tracks, vias
0, 0
Routed
Not yet
KiCad
KiCad 10.0 (file 20260206)
Created
8 Apr 2025
Updated
25 Sep 2026

Overview

Openmic 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 with 432 parts on 370 nets.

It is built around the 74AHCT125D, INA1650IPW and OPA1637DGK, with the CH224K, OPA1642AID and PTN5150AHXMP among its other parts. Its parts include 186 capacitors, 137 resistors, 49 diodes, 19 ICs and 15 switches.

Main components

12

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

432
QtyValueFootprintReferences
83100nFCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC1, C10, C101, C105, C107, C108, C109, C110, C111, C112, C113, C114, C122, C123, C126, C132 +67
34WS2812B-2020LED_SMD:LED_WS2812B-2020_PLCC4_2.0x2.0mmD1, D2, D3, D18, D19, D20, D21, D22, D23, D24, D25, D35, D36, D37, D38, D39 +18
25100nFCapacitor_SMD:C_0402_1005Metric_Pad0.74x0.62mm_HandSolderC125, C127, C128, C129, C130, C131, C133, C134, C135, C136, C137, C138, C139, C140, C141, C142 +9
2010kResistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR1, R2, R6, R7, R30, R31, R34, R35, R43, R65, R66, R67, R68, R78, R79, R113 +4
161kResistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR4, R33, R63, R69, R75, R81, R86, R91, R117, R127, R128, R129, R130, R131, R132, R133
1647kResistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR18, R32, R49, R58, R61, R71, R73, R92, R96, R98, R99, R100, R116, R135, R136, R139
1310uFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC151, C157, C158, C159, C160, C161, C162, C164, C165, C167, C177, C178, C198
1210Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR10, R13, R39, R42, R62, R72, R77, R88, R123, R124, R125, R126
1022pFCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC23, C29, C36, C37, C61, C67, C75, C76, C155, C156
102kResistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR16, R17, R23, R28, R29, R47, R48, R54, R59, R60
81k2Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR11, R14, R21, R22, R24, R27, R52, R55
847uFCapacitor_SMD:CP_Elec_6.3x5.4C18, C22, C27, C28, C33, C41, C60, C66
8510Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR19, R20, R25, R26, R50, R51, R56, R57
710uFCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC80, C81, C85, C100, C104, C106, C115
6100kResistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR45, R80, R87, R97, R134, R137
510kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR104, R106, R108, R120, R122
51MResistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR5, R12, R15, R36, R101
5DG1413EEQPackage_SO:TSSOP-16_4.4x5mm_P0.65mmSW3, SW5, SW6, SW9, SW11
4100kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR107, R111, R112, R114
4100pFCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC24, C30, C32, C34
4100uFCapacitor_SMD:CP_Elec_6.3x5.4C2, C11, C12, C13
410nFCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC102, C103, C120, C121
410uFCapacitor_SMD:CP_Elec_6.3x5.4C50, C51, C52, C53
4220pFCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC25, C26, C63, C64
46.34kResistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR64, R70, R74, R76
46k81Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR8, R9, R37, R38
475Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR138, R140, R141, R142
4BAT54SPackage_TO_SOT_SMD:SOT-23D31, D32, D33, D34
4BAV99Package_TO_SOT_SMD:SOT-23D65, D66, D67, D68
4CSD13380F3Package_DFN_QFN:Texas_PicoStar_DFN-3_0.69x0.60mmQ1, Q2, Q3, Q5
4LEDLED_SMD:LED_0603_1608Metric_Pad1.05x0.95mm_HandSolderD13, D30, D59, D63
4OPA1637Package_SO:VSSOP-8_3x3mm_P0.65mmU3, U9, U12, U13
4RotaryEncoderopenmic:PEC11LSW1, SW7, SW12, SW13
4SW_PushButton_Switch_SMD:SW_Push_1P1T_XKB_TS-1187ASW16, SW17, SW18, SW19
31uFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC169, C170, C180
31uFCapacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolderC82, C98, C99
322uFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC163, C166, C168
3OPA1612AxDPackage_SO:SOIC-8_3.9x4.9mm_P1.27mmU5, U24, U30
2100Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR41, R121
21000uFCapacitor_SMD:CP_Elec_8x10.5C14, C15
2100nFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC150, C197
22.2uFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC174, C175
22.2uHInductor_SMD:L_Wuerth_PMCI-201610L1, L2
247Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR82, R89
2470nFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC172, C173
25k1Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR85, R90
2DG1411EEQPackage_SO:TSSOP-16_4.4x5mm_P0.65mmSW4, SW10
2MBR0580Diode_SMD:D_SOD-123D64, D69
2NCJ10FI-H-0Connector_Audio:Jack_XLR-6.35mm_Neutrik_NCJ10FI-H-0_HorizontalJ3, J4
2THAT1580Package_DFN_QFN:QFN-16-1EP_4x4mm_P0.65mm_EP2.1x2.1mm_ThermalViasU2, U7
2USB_C_Receptacle_USB2.0_16PConnector_USB:USB_C_Receptacle_HRO_TYPE-C-31-M-12J7, J9
110nFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC176
1118kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR103
1127kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR109
112kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR119
11uFCapacitor_SMD:C_0402_1005Metric_Pad0.74x0.62mm_HandSolderC152
1220kResistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR93
130Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolderR102
1330kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR110
1392kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR118
14.7uFCapacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolderC171
14.7uHInductor_SMD:L_Wuerth_PMCI-201610L3
1475kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR115
1475uHopenmic:Wurth Elektronik 760390015T1
1499kResistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolderR105
1600RInductor_SMD:L_0402_1005Metric_Pad0.77x0.64mm_HandSolderFB1
174AHCT125Package_SO:SOIC-14_3.9x8.7mm_P1.27mmU16
1BAS316Diode_SMD:D_SOD-323D61
1CH224KPackage_SO:SSOP-10-1EP_3.9x4.9mm_P1mm_EP2.1x3.3mmU29
1INA1650Package_SO:TSSOP-14_4.4x5mm_P0.65mmU14
1NMJ6HHD2Connector_Audio:Jack_6.35mm_Neutrik_NMJ6HHD2_HorizontalJ8
1NSJ12HCConnector_Audio:Jack_6.35mm_Neutrik_NSJ12HC_HorizontalJ5
1OPA1622Package_SON:Texas_S-PVSON-N10U15
1OPA1642Package_SO:VSSOP-8_3x3mm_P0.65mmU6
1PTN5150AHXMPPackage_DFN_QFN:Texas_X2QFN-12_1.6x1.6mm_P0.4mmU18
1SN6505BDBVPackage_TO_SOT_SMD:SOT-23-6U21
1TAC5212openmic:TAC5212U11
1THAT5263Package_DFN_QFN:QFN-24-1EP_5x5mm_P0.65mm_EP3.4x3.4mmU1
1TKC 7M 24MHzCrystal:Crystal_SMD_TXC_7M-4Pin_3.2x2.5mm_HandSolderingY1
1TPS2116DRLPackage_TO_SOT_SMD:SOT-583-8U22

The 422 most common of 432 parts.

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Questions

What parts does the Openmic use?

432 parts, built around the 74AHCT125D, INA1650IPW, OPA1637DGK and CH224K. 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 Openmic KiCad files?

From the oliverpaddock/OpenMic repository on GitHub, at the commit this page was made from: the board is hardware/pcb/main-board/openmic.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 Openmic 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).