How to Build a Digitally-Controlled Audio Preamplifier with Red Pitaya

Introduction: From Thesis to DIY Audio Engineering 

Meet Dima Korschunov, an electrical engineering student who transformed a long-held vision into reality during his bachelor's thesis at HTWK Leipzig. His project? A sophisticated analog audio preamplifier featuring digitally-controlled crossover filters, specifically designed for reggae sound systems - where precision audio control is paramount. 

The journey began five years ago when Dima first envisioned building this preamplifier. After years of research and gathering information, he brought the concept to life over two intensive semesters of development and construction. 

What makes this project exceptional is how Red Pitaya STEMlab 125-14 became the Swiss Army knife of his development process, replacing multiple expensive lab instruments while enabling precise measurements and validation at every stage. 

Project Goals: Building a DIY Digital Audio Preamplifier 

• Objective: Design an active audio preamp with digitally adjustable crossover filters (Linkwitz-Riley style) in real time. 

• Complexity: Bridging analog circuit design, digital control, PCB layout, firmware, and desktop software. 

• Key challenge: Ensure seamless integration of all subsystems while preserving high audio fidelity. 

Why Use Red Pitaya for Audio Projects? 

Traditional instrumentation (spectrum analyzers, oscilloscopes, Bode analyzers) is expensive and disconnected. Red Pitaya gives Dima a unified platform for: 

• Bode (amplitude/phase) measurements 

• Oscilloscope traces 

• Logic / digital signal debugging 

• Spectrum and THD analysis 

• Seamless data export for MATLAB and LaTeX 

Dima: “With Red Pitaya, I could measure filter transmission, export to MATLAB, and integrate plots directly into my thesis.” 

System Architecture: Modular PCB Design and Audio Filters 

Instead of one large PCB, the preamp was split into four functional modules for easier testing and upgrades. 

Key modules: 

• Analog front end and filters
• Digital potentiometer interface
• Arduino Nano microcontroller for real-time control
• Desktop UI for end-user interaction
• Measurement and test points for Red Pitaya

Implementation: Simulation, Debugging, and Validation 

• Filter Characterization: Bode Analyzer to measure amplitude and phase across audio frequencies. 

• Digital Interface Debugging: Logic Analyzer caught subtle serial communication errors. 

• System-Level Testing: Spectrum and THD analysis ensured clean, professional-grade audio performance. 

Results: A Professional-Grade DIY Audio Preamplifier 

• Achieved a professional-grade, modular audio preamp with real-time filter control 

• Integrated measurement-driven design: every design decision was validated 

• Created a desktop UI (C#) to make filter adjustment accessible to end users 

• Demonstrated how a student project can reach high engineering standards 

Student Learnings and Future Development 

• Grounding & layout: Noise and crosstalk were nontrivial; better ground topology needed 

• Toolchain choices: Moving from Altium to KiCad promised broader accessibility 

• Next steps: Add automatic tuning via feedback (microphone + control theory) for adaptive adaptation in acoustics 

Educational Impact: Why This Project Matters 

This project proves that with the right tools, students can build professional-quality audio electronics without prohibitive lab costs. Platforms like Red Pitaya make it possible to design, measure, and validate projects end to end — bridging the gap between academia and industry. 

Getting Started & Resources 

1. Begin with a clear set of signal specs and a measurement plan. 

1. Modularize early — test subsystems separately. 

1. Use Red Pitaya’s multi-modal capabilities (Bode, logic, oscilloscope) continuously throughout development. 

1. Export early, document often — seamless export from Red Pitaya to MATLAB and thesis is a major advantage. 

Repository & References 

Dive into the full design, code, and documentation of the DiKo PreAmp on GitHub: https://github.com/dkorschu/DiKo_PreAmp 

This repository offers a comprehensive look at a student-led project that bridges analog audio engineering with digital control systems. Inside, you’ll find: 

• Modular PCB Designs: Schematics and layouts for each functional block. 

• Firmware Code: Arduino sketches for controlling digital potentiometers and filter parameters. 

• Desktop Interface: C# application for real-time user interaction. 

• Measurement Data: Exported results from Red Pitaya analyses, ready for further exploration. 

• Documentation: Detailed explanations and insights into the design and testing processes. 

Whether you’re interested in audio electronics, embedded systems, or measurement techniques, this project serves as a valuable resource. Feel free to explore, fork, or contribute to enhance and expand upon this work. 

Want to Share Your Project? 

If you’ve developed a project using Red Pitaya and would like to share it with the community, we’d love to hear from you! Please send an email to žiga.agostini@redpitaya.com with details about your project, and we’ll help showcase it.