Pi Shield Audio Project Completion

GENERATED:
I'm seeking a skilled electronics engineer to finish modifying an existing Pi Shield audio project for my personal use. The project is partially complete, but I can no longer load it due to some missing hardware components.

Key Tasks:
- Add a dual opamp for VCOM
- Integrate missing filters, capacitors, and resistors
- Check for grounding and trace errors
- Create Gerber files and pick-and-place files
- Assist in final JLCPCB order

Ideal skills and experience:
- Proficiency in circuit design and modification
- Experience with Gerber file generation
- Familiarity with JLCPCB and PCB assembly

References and documentation are already provided. Your expertise will help ensure a successful project completion.

MY BRIEF

Backstory

A few years back, I wanted to build the Monome Norns Shield, but couldn’t because the CS4270 was out of production for many years.
I noticed the CS4271 and CS4272 *were* readily available so I began modifying the original design to support the CS4272, at the same time, taking advantage of the CS4272’s differential topology to upgrade the flimsy/noisy mini headphone jack to prosumer grade balanced XLR inputs and outputs (external board)

While researching the CS4272, I came across the SuperAudioBoard (hackaday) which already had a working and tested analog supporting circuits for the CS4272 that we could bring over to the Norns mod.

Note: recently, Monome actually made their own new version of the Norns Shield (211028) that uses the CS4271 with TL072s as the input and output buffers, mostly making my work obsolete. However, it still uses the flimsy/noisy mini headphone jack and doesn’t support balanced connections.

My Problem

I still want to build my version of project, but it needs some fixes, and I can no longer load and edit my Eagle project files.


What I want you to do

1. Familiarise yourself with both the Norns and SuperAudioBoard projects.
2. Read or at least skim over pages 10-15 of the SuperAudioBoardDesignGuide.pdf which explains the implementation of the THS4521 opamps for the buffers including:
* Feedback topology and filtering
* Generating VCOM / VOCM using a dual, low-noise opamp (OPA2348)
* Necessity for large electrolytic caps on the output.

3. Load my Eagle project and notice main error: that I’ve tied VOCM to GND on the external head which is wrong.
4. Add the missing OPA2348 to generate buffered VCOM and correctly supply VOCM on all 4 of the THS4521 with that.
5. Check over anything else I’ve missed, making changes where necessary. Pay attention to clean audio with regard to EMF, digital vs analog ground etc.
6. Check over the analog and digital ground planes and make sure digital noise cant get into the analog signal paths.
7. Check I’ve set up and oriented the new crystal correctly.
8. Check for any other obvious mistakes in the schematic and board. Should be fairly easy as you hav both the Norns and SuperAudioBoard eagle files for reference.
9. Add any extra protection or extra filtering where necessary to keep the audio clean and free from digital hash from the Pi or the LCD, EMF, parasitic noise and aliasing. SuperAudioBoard should have taken care of most of this already though.
10. Feel free to improve anything that becomes obvious along the way.
11. Build the Breakout Board
12. Create the gerbers and pick and place files and help me send off the job to JLCPCB including SMD assembly of everything except the large through hole components that I can solder manually.

I will supply sch/brd that's %90 complete and I’ve already downloaded all the data sheets and reference docs you should need.