This project is about 24-bit stereo DAC, which we build for Raspberry Pi boards. This R-2R ladder DAC is developing around Intel / Altera EPM240T100C5N CPLD.
We developed this module after review the PT8211 DAC, which we tested a few months ago. Compare with PT8211 DAC, this module is capable to provide high-quality audio output with Raspbian OS.
At the testing stages, we drive this DAC with the I2S bus of the Raspberry Pi 3 Model B board. The provided device tree overlay is developed and tested on the new Raspbian Buster OS.
The audio quality of this DAC is impressive. In most of the circumstances, we test this unit using mpg123 player and got excellent results.
The MCP602 opamp of this module is capable to drive a headphone, and for the testing, we use Audio TechnicaATH-PRO500MK2BK headphones directly with this module. Also, we pair this module with several AF power amplifiers and obtained superior results. The most noticeable AF power amplifiers which offer excellent results with this system are based on STK4221, LM3886, and TA2020 ICs.
Bottom side of the DAC prototype board.
To minimize the cost, we use small SMD components with this PCB. Most of the components of this PCB design are on (1608) 0603 packages. To avoid short-circuits, and damages we recommend to assemble this PCB using SMD rework station.