These boards can be bought from http://devboardshop.com
This version has multiple changes from the previous version, like:
V 4.0A is a version with 18 Bands + Two VU meters for right and left channels.
- Can handle stereo signals.
- Display format is 18+1+1( to display 18 bands of frequencies and Left Right signal level) .
- USB adapter for easy upgrade.
- Dedicated RTC with battery back-up.
- Added two usart connectors to create cascade spectrum analyzers( to create large display from boards like this ).
- A microcontroller twice faster that previous and multiple hardware advantages that increase speed of signal processing and display rendering.
V 4.0B is a version with 20Bands.
A 3D presentation of Audio Spectrum Analyzer 4.0B: