Cheap audio measurements!
The Problem..
Most engineers are familiar with the Audio Precision line of instruments—the gold standard for high-quality audio measurements. However, even second-hand units on eBay cost thousands of dollars.
Quant Asylum devices offer a more cost-effective solution for hobbyists, but they’re still far from cheap.
You could use an oscilloscope and waveform generator for basic sweeps and FFT measurements, but their resolution and speed are limited for detailed analysis.
Another option is connecting a USB audio interface to a PC and using REW (Room EQ Wizard) or similar open-source tools. This can work well, but setup takes time, and incorrect input or output gain settings can ruin the measurement accuracy.
This Project
This project aims to provide a low-cost alternative for practical, near–real-time audio measurements.
Performance is limited by the PCM3060 codec and NE5532 input/output amplifiers, but the goal is to achieve >90 dB SNR and <−90 dB THD.
The expectation is to create a capable device for mid-grade audio measurements in analog and digital hobby projects. Powered by the RP2040, it should provide relatively fast data processing and analysis. The exact speed and accuracy remain to be seen.
Measurement Capabilities
Total Harmonic Distortion (THD and THD+N)
Signal-to-Noise Ratio (SNR)
Fast Fourier Transform (FFT)
Frequency sweeps (Bode plots)
Amplitude sweeps (transfer curves)
Crosstalk
Hardware Features
2× analog inputs
2× analog outputs
320×240 touchscreen
Selectable input impedance: 50 Ω / 1 MΩ
Monitor output for listening
As of now, it lives on a breadboard while I am figuring out the SPI display drivers and measurement algorithms in fixed point math.