Built an audio signal processing device that I use in my car.
Not sure if the details are of interest here, but I think the end result might be -- a good deal of audio DSP capability for crossovers and EQ.
Some pics and then a brief description.
ADAU1442 audio signal processor chassis:
Four Wolfson WM8524 DACs (2 Vrms ground-centered output, -89 dB THD+N, 106 dB dynamic range)
The computing core: Analog Devices ADAU1442 audio signal processor (easy to use with their SigmaStudio graphical user interface software).
ADAU1442 board top
ADAU1442 board bottom
Testing ADAU1442 and WM8524 analog outputs (DACs are "upside down" under the ADAU1442, protected by the two ground planes in the boards)
Final prototype, box open
Final ADAU1442 prototype audio signal processor
- Analog outputs: Four independent WM8524 24-bit stereo DACs (e.g. sub, midbass, midrange, tweets). 2 Vrms ground-centered output (no DC blocking caps).
- Digital Outputs: Four independent optical S/PDIF outputs (CS8406 to TOTX147). (Future plans are to use these instead of analog).
- Power: "12 volt" from car with remote turn-on/off.
- Control: Digital volume up/down and digital source select. (Possibly more in the future if needed).
- ADAU1442 Computing Highlights:
- 3584 instructions per sample at 48 kHz.
- 56-bit processing.
- 8k data RAM (up to 170 ms delay at 48 kHz).
- IIR and FIR filters, EQ and more; easy implementation with GUI software (see below).
- ADAU1442 Usability:
After I spent some time reading about various ICs that are available, it only took about four partial weekends to build and debug the box. Then another couple hours here and there to fashion the GUI in Analog's SigmaStudio software that implements my current crossover scheme.
Many of the parts are free samples; others aren't very expensive.
I'm presently using the box for active crossovers. But now that I have some processing power I'm interested in learning about how to really EQ a car audio system.