Independent PCB Design Review — CM4-based mixed-signal audio board (Gerber + netlist) Anyone

Project type: One-time review / fixed price
Deliverable: Written findings report

Overview

We're a hardware startup preparing to fabricate the first prototypes of a CM4-based electronic musical instrument. The board has been designed and routed by our manufacturing partner, and we're seeking an independent, experienced reviewer to check the layout before we commit to fabrication. This is a review only, no redesign or routing work required.

About the board

4-layer mixed-signal PCB
Raspberry Pi Compute Module 4 (CM4) as the main processor
Audio codec with analog audio input/output path
MIPI DSI display interface
I2S audio bus, I2C, USB, MIDI (TRS), and a matrix of RGB-backlit control pads
Designed in PADS; Gerbers available now, IPC-D-356 netlist to follow

What we need reviewed (in priority order)

Analog/digital ground partitioning and return-path integrity, our biggest concern
Isolation of the analog audio section from the CM4, switching regulator, and digital switching noise
Controlled-impedance routing on the I2S audio bus and MIPI display lines, including length matching
Decoupling/bypass adequacy around the CM4, codec, and power section
Power-supply layout and switching-regulator placement relative to sensitive analog
General manufacturability and any layout choices likely to raise the audio noise floor or cause EMI

We're specifically looking for judgment on signal integrity and audio performance, not just a DRC re-run. We'll provide an IPC-D-356 netlist alongside the Gerbers so connectivity can be verified, not just copper geometry.

Ideal background

Strong experience with mixed-signal and audio PCB layout
Familiarity with SoM/embedded Linux boards (Raspberry Pi CM4/CM5 a plus)
Controlled-impedance and high-speed routing experience
Able to work from Gerber + IPC-D-356 netlist

Deliverable

A written report identifying any issues, risks, or recommendations, prioritized by severity, that we can act on before fabrication. Flagging anything that would warrant a board revision is the primary goal.

Timeline & format

We have a one-week window and would prefer a fixed-price quote with a defined turnaround. Please share relevant experience with audio or mixed-signal boards, your estimated turnaround, and your fixed price.

Note: This is an unreleased, patent-pending product. We'll ask the selected reviewer to sign a short NDA before files are shared. read less