Simple USB Sound Card with PCM2904

Today you can easily buy simple USB sound card for ridiculously small amount of money. But if you have some time and maybe, same as I, some spare PCM2904 parts in your drawer, why not creating the sound card yourself?

Features: Stereo analog line input and output, bus-powered, buttons for volume control through HID, 16-Bit Delta-Sigma ADC and DAC, sampling rates up to 48 kHz
Advantages: Single-sided PCB can easily be created at home. Card can be integrated into bigger projects.
Limitations: Output requires impedance at least 10 kΩ, so you cannot connect your headphones directly.
Eagle project including PCB: PCM2904DAC_ADC.tar.gz

The PCM2904 from Texas Instruments is little bit older, but as of today still active audio codec. It provides full ADC and DAC support with just few additional components. Circuit presented on these pages is not very innovative in any way, it is more or less standard catalog connection from the datasheet with analog supply inspiration taken from similar project. Following schematics depicts the final result:

The goal was to create a circuit which can be easily constructed in a hobby environment. This means using ideally single-sided PCB with just several wire connections form the top side and big 1206 SMD or through-hole parts. Input and output connection is realized using Jack connectors attached through PCB Headers connectors. Similar approach has been chosen for the control buttons connection. This allows placing the board into some nice box.

People interested in building or customizing and building this project can find full Eagle project files at the top of this page. Prototype was fully working as expected and with careful board manufacturing and parts soldering, everything works on the first power-up. Just please be aware of the minimum required impedance when connecting any load.

Feel free to mail me your opinions or remarks.