Yamaha CP70 Electric Grand Piano - 72 Channel Pre-amplifier Project

https://www.pomeindhoven.nl/

Paviljoen Ongehoorde Muziek
Vestdijk 25 - 5611 CA
Eindhoven

Project Overview

This repository contains the KiCad project files, documentation, and design decisions for a custom-built 72-channel pre-amplifier designed for a Yamaha CP70 electric grand piano. This project is an open-source initiative developed in collaboration with Paviljoen Ongehoorde Muziek (POM) in Eindhoven, Netherlands, as part of an art project.

The primary goal of this pre-amplifier is to individually buffer and potentially amplify the signals from each of the 72 string pickups of the CP70, providing a high-quality, low-noise output output signal for further amplification to 72 speakers.

Repository URL: https://github.com/edwin-oetelaar/CP70_preamp/tree/main

Image of the piano

Background

The Yamaha CP70 is an iconic electric grand piano known for its unique sound, derived from real strings and hammers combined with a piezo pickup system.
This project aims to provide a modern, high-fidelity replacement, with 72 separate output channels as an alternative pre-amplifier system.

This pre-amp is designed with the following considerations:

High Input Impedance: To accurately capture the full tonal character of the CP70 pickups without loading them down.
Low Noise Performance: Essential for a clean signal, especially with 72 individual channels.
Sufficient Headroom: To handle the potentially large signal swings from the pickups.
Individual Channel Processing: Each pickup receives its own pre-amplifier stage.
Modularity: For ease of assembly, testing, and maintenance.
Open Source: All design files and documentation are publicly available to encourage learning, modification, accessibility.

Project Status

[ TODO: Update this section regularly, e.g., In Design, Prototyping, Tested, In Use ]

Current Version: [e.g., v0.1 - Initial Design]
Key Milestones:
- Initial schematic design complete.
- PCB layout for [16]-channel module complete.
- PCB ordered
- parts ordered
- First prototype(s) built and tested.
- Full 72-channel system assembled.
- Integration with the CP70 at Paviljoen Ongehoorde Muziek.

Design Files and Documentation

This repository is structured to include:

/kicad_project: Contains the KiCad schematic and PCB layout files.
- CP70_preamp.kicad_pro - Main KiCad project file.
- CP70_preamp.kicad_sch - Main schematic file.
- CP70_preamp.kicad_pcb - Main PCB layout file (or individual module files).
- libraries/ - Custom schematic symbols and PCB footprints, if any.
- out1/ - Gerber files for PCB manufacturing (to be added when ready). (file out1.zip sent to JLCPCB)
- bom/ - Bill of Materials (to be added).
/documentation:
- design_decisions.md - Detailed explanation of the design choices, component selection, and rationale.
- specifications.md - Target specifications for the pre-amplifier.
- testing_procedure.md - (To be added) How to test individual modules and the full system.
- Images, block diagrams, and other supporting documents.
/images: Schematics, photos of prototypes, etc.
README.md - This file.

image of version 0.1 printed circuit board

Key Design Aspects (Summary)

Number of Channels: 72 (one for each pickup)
Input Stage: High-impedance buffer for each channel.
- Target Input Impedance: 470K Ω
- Expected Pickup Output: Up to 45V peak-to-peak in 1 M (requiring input attenuation).
Operational Amplifier: [e.g., TL072 or similar, specify your choice and link to design_decisions.md]
Power Supply: Symmetrical (e.g., +/-15V or +/-18V)
Gain: [e.g., Unity gain buffer, or variable gain via potentiometer - specify and link to design_decisions.md]

More detailed information on architecture, component choices, and trade-offs can be found in /documentation/design_decisions.md.

Getting Started / How to Use

Clone the repository:

git clone https://github.com/edwin-oetelaar/CP70_preamp.git
cd CP70_preamp

Open in KiCad: Open the CP70_preamp.kicad_pro file in KiCad (Latest version).
Review Schematics and PCB Layout: Explore the design in the KiCad schematic editor and PCB editor.
Check Documentation: Read through the design_decisions.md and other documents for a deeper understanding.

Contributing

This is an open-source project, and contributions or suggestions are welcome! If you have ideas, find bugs, or want to contribute to the design:

Fork the repository.
Create a new branch for your feature or bug fix.
Make your changes.
Submit a Pull Request with a clear description of your changes.

You can also open an Issue to report bugs or suggest improvements.

Collaboration

This project is in proud collaboration with:

Paviljoen Ongehoorde Muziek (POM)
Vestdijk 25 - 5611 CA Eindhoven
https://www.pomeindhoven.nl/

The pre-amplifier is intended for use in an art project hosted at POM.

License

This project is licensed under the MIT License - see the LICENSE.md file for details.

Contact

For questions or discussions regarding this project, you can contact:

Edwin van den Oetelaar - Leave a message in the issue tracker or google my name/email
Or open an issue on this GitHub repository.

edwin-oetelaar/CP70_preamp