24-bit Stereo Audio DAC for Raspberry Pi

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.

A finished prototype of the R-2R DAC.

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 Technica ATH-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.

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.

This is an open hardware project. All the contents including RTL source codes, configuration scripts, schematics and design files of this project are available at the GitHub repository.

Comments

Mio Taalas said…
Sure it's great for educational purposes and to learn stuff, but it's not really 24bit since you'll lose quite a bit (pun intended) for noise in the resistors themselves and in general noise since the surface area of the board and DAC is quite large. Not to even mention powersupply noise etc. etc.

Nice project regardless... you could talk about the drawbacks and the real performance as well so people get better understanding on how difficult it is to design DAC's :)
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