2 layers37 × 51 mm ElectretXLRMic, the printed circuit board in 3D

ElectretXLRMic

Phantom powered OPA Alice / https://www.ti.com/lit/an/sboa320a/sboa320a.pdf?ts=1773332275188 resembling Electret mic Impedance Converter with balanced out.

Full screen GitHub .kicad_pcb

Size: 37 × 51 mm
Copper layers: 2
Thickness: 1.6 mm
Parts: 38
Nets: 12
Pads: 72
Tracks, vias: 75, 235
Pours: 80
Routed: Yes
KiCad: KiCad 10.0 (file 20260206)
Created: 13 Mar 2026
Updated: 21 Apr 2026

Overview

ElectretXLRMic is an open-source printed circuit board by MHeis22, from the MHeis22/P48ElectretMicPCB repository on GitHub. It is a 2-layer board of 37 × 51 mm with 38 parts on 12 nets, routed with 75 tracks and 235 vias.

It is built around the OPA1678ID and SMAJ58CA. Its parts include 10 capacitors, 9 resistors, 3 diodes, 2 connectors and 1 IC.

Main components

README

README.md

Ordered the PCBs from JLCPCB and components from Mouser. Initial test on 26.3.26 provided great results. Noticeably less bass heavy than the Fifine K688 which was used with XLR. Both microphones tested on a Scarlett 2i2 4th generation.

🛠 Technical Hardware Summary

Autogenerated by GitHub Command Center

📋 Project Overview

Metric	Value
Board Dimensions	37.0 x 51.01 mm
Total Area	1887.24 mm²
Layer Count	2 Copper Layers
Total Components	27
SMD Components	21
THT Components	4
Unique Parts	25
KiCad Version	10.0.1

📐 Manufacturing & DRC

Metric	Value
Vias	235 Total (235 TH, 0 Blind, 0 Micro)

📄 Architecture

Power Domains: GND

⚙️ Mechanical

Mounting Holes: 2 (H2 (MountingHole_2.7mm_M2.5_DIN965_Pad_TopBottom), H1 (MountingHole_2.5mm))

🚫 Do Not Populate (DNP)

J3 (XLR3)

🧠 Core ICs & Modules

Reference	Component	Function / Description
U1	OPA1678	Low-Distortion Audio Operational Amplifiers, SOIC-8/VSSOP-8

🔌 Connectors & Interfaces

Reference	Type	Component	Description
J2	Connector	MIC	Generic connector, single row, 01x02, script generated
J1	Connector	XLR3	Header for XLR pins
J3	Connector	XLR3	XLR Connector, Female, 3 Pins

📏 Passive Components

Component	Breakdown
Capacitor	5x0603 and 5xOther
Diode	3xOther
Resistor	9x0603

Project files

Show this board on your page

https://pcbkit.io/boards/MHeis22/P48ElectretMicPCB

The board's own page, for a message or a post.

Source

Repository: MHeis22/P48ElectretMicPCB
Board file: ElectretXLRMic.kicad_pcb
Commit: 457863b
Licence: Not stated

Parts

Qty	Value	Footprint	References
4	GND1	TestPoint:TestPoint_Pad_2.0x2.0mm	TP1, TP2, TP8, TP10
3	100pF	Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolder	C3, C5, C6
2	100	Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder	R1, R2
2	1k	Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder	R5, R7
2	1uF	Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolder	C7, C8
2	2.2k	Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder	R4, R6
2	3.3uF	Capacitor_THT:C_Rect_L10.3mm_W5.7mm_P7.50mm_MKS4	C1, C4
2	33uF	Capacitor_SMD:C_Elec_8x10.2	C9, C10
2	SMAJ58CA	Diode_SMD:D_SMA	D1, D3
1	100k	Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder	R3
1	10uF	SamacSys_Parts:CAPAE660X850N	C2
1	330	Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder	R8
1	7.5k	Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder	R9
1	D_Zener 8.2V	Diode_SMD:D_SOD-123	D2
1	MIC	Connector_PinHeader_2.00mm:PinHeader_1x02_P2.00mm_Vertical	J2
1	MountingHole	MountingHole:MountingHole_2.5mm	H1
1	MountingHole_GND	MountingHole:MountingHole_2.7mm_M2.5_DIN965_Pad_TopBottom	H2
1	OPA1678	Package_SO:SOIC-8_3.9x4.9mm_P1.27mm	U1
1	U1A+	TestPoint:TestPoint_Pad_2.0x2.0mm	TP6
1	U1AOUT	TestPoint:TestPoint_Pad_2.0x2.0mm	TP4
1	U1BOUT	TestPoint:TestPoint_Pad_2.0x2.0mm	TP5
1	VCC	TestPoint:TestPoint_Pad_2.0x2.0mm	TP11
1	XLR2	TestPoint:TestPoint_Pad_2.0x2.0mm	TP3
1	XLR3	TestPoint:TestPoint_Pad_2.0x2.0mm	TP9
1	XLR3	Connector_PinHeader_2.54mm:PinHeader_1x03_P2.54mm_Vertical	J1
1	Zener	TestPoint:TestPoint_Pad_2.0x2.0mm	TP7

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Questions

How big is the ElectretXLRMic PCB?

It measures 37 × 51 mm and has 2 copper layers, 1.6 mm thick.

What parts does the ElectretXLRMic use?

38 parts, built around the OPA1678ID and SMAJ58CA. 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 ElectretXLRMic KiCad files?

From the MHeis22/P48ElectretMicPCB repository on GitHub, at the commit this page was made from: the board is ElectretXLRMic.kicad_pcb and its schematic ElectretXLRMic.kicad_sch. PCBKit opens the board in the browser, with nothing to install.

Can I use the ElectretXLRMic design in my own project?

Its repository states no licence, so its author keeps all rights: ask MHeis22 before reusing the design.